1
|
Zhu X, Luo X, Deng Y, Wei H, Feng Peng, Ying L, Huang F, Hu Y, Jin Y. Doping bilayer hole-transport polymer strategy stabilizing solution-processed green quantum-dot light-emitting diodes. SCIENCE ADVANCES 2024; 10:eado0614. [PMID: 39151002 PMCID: PMC11328901 DOI: 10.1126/sciadv.ado0614] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2024] [Accepted: 07/11/2024] [Indexed: 08/18/2024]
Abstract
Quantum-dot light-emitting diodes (QLEDs) are solution-processed electroluminescence devices with great potential as energy-saving, large-area, and low-cost display and lighting technologies. Ideally, the organic hole-transport layers (HTLs) in QLEDs should simultaneously deliver efficient hole injection and transport, effective electron blocking, and robust electrochemical stability. However, it is still challenging for a single HTL to fulfill all these stringent criteria. Here, we demonstrate a general design of doping-bilayer polymer-HTL architecture for stabilizing high-efficiency QLEDs. We show that the bilayer HTLs combining the electrochemical-stable polymer and the electron-blocking polymer unexpectedly increase the hole injection barrier. We mitigated the problem by p-doping of the underlying sublayer of the bilayer HTLs. Consequently, green QLEDs with an unprecedented maximum luminance of 1,340,000 cd m-2 and a record-long operational lifetime (T95 lifetime at an initial luminance of 1000 cd m-2 is 17,700 hours) were achieved. The universality of the strategy is examined in various polymer-HTL systems, providing a general route toward high-performance solution-processed QLEDs.
Collapse
Affiliation(s)
- Xitong Zhu
- State Key Laboratory of Silicon and Advanced Semiconductor Materials, Key Laboratory of Excited-State Materials of Zhejiang Province, Department of Chemistry, Zhejiang University, Hangzhou 310027, China
| | - Xiao Luo
- State Key Laboratory of Silicon and Advanced Semiconductor Materials, Key Laboratory of Excited-State Materials of Zhejiang Province, Department of Chemistry, Zhejiang University, Hangzhou 310027, China
| | - Yunzhou Deng
- State Key Laboratory of Silicon and Advanced Semiconductor Materials, Key Laboratory of Excited-State Materials of Zhejiang Province, Department of Chemistry, Zhejiang University, Hangzhou 310027, China
- Cavendish Laboratory, University of Cambridge, Cambridge, UK
| | - Huan Wei
- International Science and Technology Innovation Cooperation Base for Advanced Display Technologies of Hunan Province, School of Physics and Electronics, Hunan University, Changsha 410082, China
| | - Feng Peng
- Dongguan Volt-Amp Optoelectronics Technology Co. Ltd., Dongguan 523808, China
| | - Lei Ying
- Dongguan Volt-Amp Optoelectronics Technology Co. Ltd., Dongguan 523808, China
- Institute of Polymer Optoelectronic Materials and Devices, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, China
| | - Fei Huang
- Institute of Polymer Optoelectronic Materials and Devices, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, China
| | - Yuanyuan Hu
- International Science and Technology Innovation Cooperation Base for Advanced Display Technologies of Hunan Province, School of Physics and Electronics, Hunan University, Changsha 410082, China
| | - Yizheng Jin
- State Key Laboratory of Silicon and Advanced Semiconductor Materials, Key Laboratory of Excited-State Materials of Zhejiang Province, Department of Chemistry, Zhejiang University, Hangzhou 310027, China
| |
Collapse
|
2
|
Shen Q, Sun X, Chen S. Electrode Doping and Dielectric Effect in Hole Injection into Organic Semiconductors through High Work-Function Oxides. J Phys Chem Lett 2023; 14:4830-4836. [PMID: 37192342 DOI: 10.1021/acs.jpclett.3c00770] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
High work-function metal oxides are common for enhancing hole injection into organic semiconductors. However, the current understanding of the electrostatic mechanism needs to be more consistent with materials' electronic properties. Here, we study the electrostatic profile of high work-function oxides by considering their dielectricity and energetic disorder. Using MoO3 as an example, we first show that the significant vacuum-level change at the electrode-oxide interface originates from electrode doping rather than the conventionally assumed interface dipole. Moreover, electrode doping is enough to explain the Fermi-level shift, so MoO3's characteristic n-type property is not necessarily due to intrinsic donors. This conclusion also applies to the n-type oxides with reduced work functions, like WO3, V2O5, and p-type NiO. Finally, the dielectricity of the oxide, either n-type or p-type, reduces the surface p-doping of the further deposited organic layer. Increasing the oxide's metallicity and energetic disorder facilitates the hole injection.
Collapse
Affiliation(s)
- Qi Shen
- Suzhou Key Laboratory of Novel Semiconductor-optoelectronics Materials and Devices, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, Jiangsu, China
| | - Xiaojuan Sun
- Suzhou Key Laboratory of Novel Semiconductor-optoelectronics Materials and Devices, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, Jiangsu, China
| | - Song Chen
- Suzhou Key Laboratory of Novel Semiconductor-optoelectronics Materials and Devices, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, Jiangsu, China
- Jiangsu Key Laboratory of Advanced Negative Carbon Technologies, Soochow University, Suzhou 215123, Jiangsu, PR China
| |
Collapse
|
3
|
Rijal K, Amos S, Valencia-Acuna P, Rudayni F, Fuller N, Zhao H, Peelaers H, Chan WL. Nanoscale Periodic Trapping Sites for Interlayer Excitons Built by Deformable Molecular Crystal on 2D Crystal. ACS NANO 2023; 17:7775-7786. [PMID: 37042658 DOI: 10.1021/acsnano.3c00541] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
The nanoscale moiré pattern formed at 2D transition-metal dichalcogenide crystal (TMDC) heterostructures provides periodic trapping sites for excitons, which is essential for realizing various exotic phases such as artificial exciton lattices, Bose-Einstein condensates, and exciton insulators. At organic molecule/TMDC heterostructures, similar periodic potentials can be formed via other degrees of freedom. Here, we utilize the structure deformability of a 2D molecular crystal as a degree of freedom to create a periodic nanoscale potential that can trap interlayer excitons (IXs). Specifically, two semiconducting molecules, PTCDI and PTCDA, which possess similar band gaps and ionization potentials but form different lattice structures on MoS2, are investigated. The PTCDI lattice on MoS2 is distorted geometrically, which lifts the degeneracy of the two molecules within the crystal's unit cell. The degeneracy lifting results in a spatial variation of the molecular orbital energy, with an amplitude and periodicity of ∼0.2 eV and ∼2 nm, respectively. On the other hand, no such energy variation is observed in PTCDA/MoS2, where the PTCDA lattice is much less distorted. The periodic variation in molecular orbital energies provides effective trapping sites for IXs. For IXs formed at PTCDI/MoS2, rapid spatial localization of the electron in the organic layer toward the interface is observed, which demonstrates the effectiveness of these interfacial IX traps.
Collapse
Affiliation(s)
- Kushal Rijal
- Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, United States
| | - Stephanie Amos
- Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, United States
| | - Pavel Valencia-Acuna
- Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, United States
| | - Fatimah Rudayni
- Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, United States
- Department of Physics, Jazan University, Jazan 45142, Saudi Arabia
| | - Neno Fuller
- Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, United States
| | - Hui Zhao
- Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, United States
| | - Hartwin Peelaers
- Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, United States
| | - Wai-Lun Chan
- Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, United States
| |
Collapse
|
4
|
Ślęczkowski P. Spectroscopic and Spectroelectrochemical Studies of Hexapentyloxytriphenylene-A Model Discotic Molecule. Int J Mol Sci 2023; 24:ijms24086924. [PMID: 37108088 PMCID: PMC10139095 DOI: 10.3390/ijms24086924] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2023] [Revised: 03/27/2023] [Accepted: 04/06/2023] [Indexed: 04/29/2023] Open
Abstract
The electrochemical and spectroelectrochemical properties of the discotic mesogen 2,3,6,7,10,11-pentyloxytriphenylene (H5T) were studied with the use of cyclic voltammetry combined with UV-Vis and electron paramagnetic resonance (EPR) spectroscopy in solution. The UV-Vis absorption spectroscopy of H5T in dichloromethane showed its monomeric state in a concentration range up to 10-3 mol dm-3. The reversible process of the electrochemical formation of the radical cation was evidenced within the experimentally accessible potential window. The in situ UV-Vis spectroelectrochemical measurements further enabled identification of the product of the redox process and evaluation of the effect of aggregation in the concentration range of 5 × 10-3 mol dm-3. The results are discussed in the frame of solvent effects on the self-assembly propensity of solute molecules, in a wide range of concentrations. In particular, the crucial role of the solvent polarity is indicated, which contributes to the understanding of solution effects and pre-programming of supramolecular organic materials, in particular anisotropic disc-shaped hexa-substituted triphenylenes.
Collapse
Affiliation(s)
- Piotr Ślęczkowski
- International Centre for Research on Innovative Biobased Materials (ICRI-BioM)-International Research Agenda, Lodz University of Technology, Zeromskiego 116, 90-924 Lodz, Poland
| |
Collapse
|
5
|
Yu ZD, Lu Y, Wang ZY, Un HI, Zelewski SJ, Cui Y, You HY, Liu Y, Xie KF, Yao ZF, He YC, Wang JY, Hu WB, Sirringhaus H, Pei J. High n-type and p-type conductivities and power factors achieved in a single conjugated polymer. SCIENCE ADVANCES 2023; 9:eadf3495. [PMID: 36827372 PMCID: PMC9956111 DOI: 10.1126/sciadv.adf3495] [Citation(s) in RCA: 15] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/15/2022] [Accepted: 01/25/2023] [Indexed: 06/18/2023]
Abstract
The charge transport properties of conjugated polymers are commonly limited by the energetic disorder. Recently, several amorphous conjugated polymers with planar backbone conformations and low energetic disorder have been investigated for applications in field-effect transistors and thermoelectrics. However, there is a lack of strategy to finely tune the interchain π-π contacts of these polymers that severely restricts the energetic disorder of interchain charge transport. Here, we demonstrate that it is feasible to achieve excellent conductivity and thermoelectric performance in polymers based on thiophene-fused benzodifurandione oligo(p-phenylenevinylene) through reducing the crystallization rate of side chains and, in this way, carefully controlling the degree of interchain π-π contacts. N-type (p-type) conductivities of more than 100 S cm-1 (400 S cm-1) and power factors of more than 200 μW m-1 K-2 (100 μW m-1 K-2) were achieved within a single polymer doped by different dopants. It further demonstrated the state-of-the-art power output of the first flexible single-polymer thermoelectric generator.
Collapse
Affiliation(s)
- Zi-Di Yu
- Beijing National Laboratory for Molecular Sciences (BNLMS), Key Laboratory of Polymer Chemistry and Physics of Ministry of Education, Center of Soft Matter Science and Engineering, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
| | - Yang Lu
- Beijing National Laboratory for Molecular Sciences (BNLMS), Key Laboratory of Polymer Chemistry and Physics of Ministry of Education, Center of Soft Matter Science and Engineering, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
| | - Zi-Yuan Wang
- Beijing National Laboratory for Molecular Sciences (BNLMS), Key Laboratory of Polymer Chemistry and Physics of Ministry of Education, Center of Soft Matter Science and Engineering, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
| | - Hio-Ieng Un
- Optoelectronics Group, Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, UK
| | - Szymon J. Zelewski
- Optoelectronics Group, Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, UK
- Department of Semiconductor Materials Engineering, Faculty of Fundamental Problems of Technology, Wrocław University of Science and Technology, Wybrzeże Wyspiańskiego 27, Wrocław 50-370, Poland
| | - Ying Cui
- Department of Polymer Science and Engineering, State Key Lab of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Hao-Yang You
- Beijing National Laboratory for Molecular Sciences (BNLMS), Key Laboratory of Polymer Chemistry and Physics of Ministry of Education, Center of Soft Matter Science and Engineering, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
| | - Yi Liu
- Beijing National Laboratory for Molecular Sciences (BNLMS), Key Laboratory of Polymer Chemistry and Physics of Ministry of Education, Center of Soft Matter Science and Engineering, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
| | - Ke-Feng Xie
- Department of Polymer Science and Engineering, State Key Lab of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Ze-Fan Yao
- Beijing National Laboratory for Molecular Sciences (BNLMS), Key Laboratory of Polymer Chemistry and Physics of Ministry of Education, Center of Soft Matter Science and Engineering, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
| | - Yu-Cheng He
- Department of Polymer Science and Engineering, State Key Lab of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Jie-Yu Wang
- Beijing National Laboratory for Molecular Sciences (BNLMS), Key Laboratory of Polymer Chemistry and Physics of Ministry of Education, Center of Soft Matter Science and Engineering, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
| | - Wen-Bing Hu
- Department of Polymer Science and Engineering, State Key Lab of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Henning Sirringhaus
- Optoelectronics Group, Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, UK
| | - Jian Pei
- Beijing National Laboratory for Molecular Sciences (BNLMS), Key Laboratory of Polymer Chemistry and Physics of Ministry of Education, Center of Soft Matter Science and Engineering, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
| |
Collapse
|
6
|
Ni Y, Feng J, Liu J, Yu H, Wei H, Du Y, Liu L, Sun L, Zhou J, Xu W. An Artificial Nerve Capable of UV-Perception, NIR-Vis Switchable Plasticity Modulation, and Motion State Monitoring. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2022; 9:e2102036. [PMID: 34716679 PMCID: PMC8728819 DOI: 10.1002/advs.202102036] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2021] [Revised: 08/26/2021] [Indexed: 06/02/2023]
Abstract
The first flexible organic-heterojunction neuromorphic transistor (OHNT) that senses broadband light, including near-ultraviolet (NUV), visible (vis), and near-infrared (NIR), and processes multiplexed-neurotransmission signals is demonstrated. For UV perception, electrical energy consumption down to 536 aJ per synaptic event is demonstrated, at least one order of magnitude lower than current UV-sensitive synaptic devices. For NIR- and vis-perception, switchable plasticity by alternating light sources is yielded for recognition and memory. The device emulates multiplexed neurochemical transition of different neurotransmitters such as dopamine and noradrenaline to form short-term and long-term responses. These facilitate the first realization of human-integrated motion state monitoring and processing using a synaptic hardware, which is then used for real-time heart monitoring of human movement. Motion state analysis with the 96% accuracy is then achieved by artificial neural network. This work provides important support to future biomedical electronics and neural prostheses.
Collapse
Affiliation(s)
- Yao Ni
- Institute of Photoelectronic Thin Film Devices and Technology of Nankai UniversityTianjin300350P. R. China
- Key Laboratory of Optoelectronic Thin Film Devices and Technology of TianjinTianjin300350P. R. China
- Engineering Research Center of Thin Film Optoelectronics Technology of Ministry of EducationNankai UniversityTianjin300350P. R. China
- College of Electronic Information and Optical Engineering of Nankai UniversityNational Institute for Advanced MaterialsNankai UniversityTianjin300350P. R. China
| | - Jiulong Feng
- Institute of Photoelectronic Thin Film Devices and Technology of Nankai UniversityTianjin300350P. R. China
- Key Laboratory of Optoelectronic Thin Film Devices and Technology of TianjinTianjin300350P. R. China
- Engineering Research Center of Thin Film Optoelectronics Technology of Ministry of EducationNankai UniversityTianjin300350P. R. China
- College of Electronic Information and Optical Engineering of Nankai UniversityNational Institute for Advanced MaterialsNankai UniversityTianjin300350P. R. China
| | - Jiaqi Liu
- Institute of Photoelectronic Thin Film Devices and Technology of Nankai UniversityTianjin300350P. R. China
- Key Laboratory of Optoelectronic Thin Film Devices and Technology of TianjinTianjin300350P. R. China
- Engineering Research Center of Thin Film Optoelectronics Technology of Ministry of EducationNankai UniversityTianjin300350P. R. China
- College of Electronic Information and Optical Engineering of Nankai UniversityNational Institute for Advanced MaterialsNankai UniversityTianjin300350P. R. China
| | - Hang Yu
- College of Microelectronics and Communication EngineeringChongqing UniversityChongqing400044P. R. China
- No. 24 Research Institute of China Electronics Technology Group CorporationChongqing400060P. R. China
| | - Huanhuan Wei
- Institute of Photoelectronic Thin Film Devices and Technology of Nankai UniversityTianjin300350P. R. China
- Key Laboratory of Optoelectronic Thin Film Devices and Technology of TianjinTianjin300350P. R. China
- Engineering Research Center of Thin Film Optoelectronics Technology of Ministry of EducationNankai UniversityTianjin300350P. R. China
- College of Electronic Information and Optical Engineering of Nankai UniversityNational Institute for Advanced MaterialsNankai UniversityTianjin300350P. R. China
| | - Yi Du
- Institute of Photoelectronic Thin Film Devices and Technology of Nankai UniversityTianjin300350P. R. China
- Key Laboratory of Optoelectronic Thin Film Devices and Technology of TianjinTianjin300350P. R. China
- Engineering Research Center of Thin Film Optoelectronics Technology of Ministry of EducationNankai UniversityTianjin300350P. R. China
- College of Electronic Information and Optical Engineering of Nankai UniversityNational Institute for Advanced MaterialsNankai UniversityTianjin300350P. R. China
| | - Lu Liu
- Institute of Photoelectronic Thin Film Devices and Technology of Nankai UniversityTianjin300350P. R. China
- Key Laboratory of Optoelectronic Thin Film Devices and Technology of TianjinTianjin300350P. R. China
- Engineering Research Center of Thin Film Optoelectronics Technology of Ministry of EducationNankai UniversityTianjin300350P. R. China
- College of Electronic Information and Optical Engineering of Nankai UniversityNational Institute for Advanced MaterialsNankai UniversityTianjin300350P. R. China
| | - Lin Sun
- Institute of Photoelectronic Thin Film Devices and Technology of Nankai UniversityTianjin300350P. R. China
- Key Laboratory of Optoelectronic Thin Film Devices and Technology of TianjinTianjin300350P. R. China
- Engineering Research Center of Thin Film Optoelectronics Technology of Ministry of EducationNankai UniversityTianjin300350P. R. China
- College of Electronic Information and Optical Engineering of Nankai UniversityNational Institute for Advanced MaterialsNankai UniversityTianjin300350P. R. China
| | - Jianlin Zhou
- College of Microelectronics and Communication EngineeringChongqing UniversityChongqing400044P. R. China
| | - Wentao Xu
- Institute of Photoelectronic Thin Film Devices and Technology of Nankai UniversityTianjin300350P. R. China
- Key Laboratory of Optoelectronic Thin Film Devices and Technology of TianjinTianjin300350P. R. China
- Engineering Research Center of Thin Film Optoelectronics Technology of Ministry of EducationNankai UniversityTianjin300350P. R. China
- College of Electronic Information and Optical Engineering of Nankai UniversityNational Institute for Advanced MaterialsNankai UniversityTianjin300350P. R. China
| |
Collapse
|
7
|
Wan P, Chen X, Liu Q, Mahadevan S, Guo M, Qiu J, Sun X, Tsang SW, Zhang M, Li Y, Chen S. Direct Observation of the Charge Transfer States from a Non-Fullerene Organic Solar Cell with a Small Driving Force. J Phys Chem Lett 2021; 12:10595-10602. [PMID: 34695357 DOI: 10.1021/acs.jpclett.1c03365] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
For organic solar cells (OSCs), the charge generation mechanism and the recombination loss are heavily linked with charge transfer states (CTS). Measuring the energy of CTS (ECT) by the most widely used technique, however, has become challenging for the non-fullerene-based OSCs with a small driving force, resulting in difficulty in the understanding of OSC physics. Herein, we present a study of the PM6:Y6 bulk heterojunction. It is demonstrated that electro-absorption can not only reveal the dipolar nature of Y6 but also resolve the morphology-dependent absorption signal of CTS in the sub-bandgap region. The device with the optimum blending weight ratio shows an ECT of 1.27 eV, which is confirmed by independent measurements. Because of the charge transfer characteristics of Y6, the charge generation at PM6:Y6 interfaces occurs efficiently under a small but non-negligible driving force of 0.14 eV, and the total recombination loss is as low as 0.43 eV.
Collapse
Affiliation(s)
- Peng Wan
- College of Chemistry, Chemical Engineering and Materials Science, Soochow University, 199 Ren'ai Road, Suzhou 215123, PR China
| | - Xingtong Chen
- College of Chemistry, Chemical Engineering and Materials Science, Soochow University, 199 Ren'ai Road, Suzhou 215123, PR China
| | - Qi Liu
- State and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials, Laboratory of Advanced Optoelectronic Materials, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, 199 Ren'ai Road, Suzhou 215123, PR China
| | - Sudhi Mahadevan
- Department of Materials Science and Engineering, City University of Hong Kong, 83 Tat Chee Avenue, Hong Kong SAR 999077, China
| | - Mingxuan Guo
- College of Chemistry, Chemical Engineering and Materials Science, Soochow University, 199 Ren'ai Road, Suzhou 215123, PR China
| | - Jinjing Qiu
- State and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials, Laboratory of Advanced Optoelectronic Materials, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, 199 Ren'ai Road, Suzhou 215123, PR China
| | - Xiaojuan Sun
- College of Chemistry, Chemical Engineering and Materials Science, Soochow University, 199 Ren'ai Road, Suzhou 215123, PR China
| | - Sai-Wing Tsang
- Department of Materials Science and Engineering, City University of Hong Kong, 83 Tat Chee Avenue, Hong Kong SAR 999077, China
| | - Maojie Zhang
- State and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials, Laboratory of Advanced Optoelectronic Materials, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, 199 Ren'ai Road, Suzhou 215123, PR China
| | - Yongfang Li
- State and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials, Laboratory of Advanced Optoelectronic Materials, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, 199 Ren'ai Road, Suzhou 215123, PR China
| | - Song Chen
- College of Chemistry, Chemical Engineering and Materials Science, Soochow University, 199 Ren'ai Road, Suzhou 215123, PR China
| |
Collapse
|
8
|
Wang Z, Lin H, Zhang X, Li J, Chen X, Wang S, Gong W, Yan H, Zhao Q, Lv W, Gong X, Xiao Q, Li F, Ji D, Zhang X, Dong H, Li L, Hu W. Revealing molecular conformation-induced stress at embedded interfaces of organic optoelectronic devices by sum frequency generation spectroscopy. SCIENCE ADVANCES 2021; 7:7/16/eabf8555. [PMID: 33853785 PMCID: PMC8050595 DOI: 10.1126/sciadv.abf8555] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2020] [Accepted: 02/25/2021] [Indexed: 05/28/2023]
Abstract
Interface stresses are pervasive and critical in conventional optoelectronic devices and generally lead to many failures and reliability problems. However, detection of the interface stress embedded in organic optoelectronic devices is a long-standing problem, which causes the unknown relationship between interface stress and organic device stability (one key and unsettled issue for practical applications). In this study, a kind of previously unknown molecular conformation-induced stress is revealed at the organic embedded interface through sum frequency generation (SFG) spectroscopy technique. This stress can be greater than 10 kcal/mol per nm2 and is sufficient to induce molecular disorder in the organic semiconductor layer (with energy below 8 kcal/mol per nm2), finally causing instability of the organic transistor. This study not only reveals interface stress in organic devices but also correlates instability of organic devices with the interface stress for the first time, offering an effective solution for improving device stability.
Collapse
Affiliation(s)
- Zhongwu Wang
- Tianjin Key Laboratory of Molecular Optoelectronic Sciences, Department of Chemistry, Institute of Molecular Aggregation Science, Tianjin University, Tianjin 300072, China
| | - Hongzhen Lin
- Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123, China
| | - Xi Zhang
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - Jie Li
- Tianjin Key Laboratory of Molecular Optoelectronic Sciences, Department of Chemistry, Institute of Molecular Aggregation Science, Tianjin University, Tianjin 300072, China
| | - Xiaosong Chen
- Tianjin Key Laboratory of Molecular Optoelectronic Sciences, Department of Chemistry, Institute of Molecular Aggregation Science, Tianjin University, Tianjin 300072, China
| | - Shuguang Wang
- Tianjin Key Laboratory of Molecular Optoelectronic Sciences, Department of Chemistry, Institute of Molecular Aggregation Science, Tianjin University, Tianjin 300072, China
| | - Wenbin Gong
- Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123, China
| | - Hui Yan
- School of Pharmaceutical Sciences, Liaocheng University, Liaocheng 252059, China
| | - Qiang Zhao
- College of Science, Civil Aviation University of China, Tianjin 300300, China
| | - Weibang Lv
- Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123, China
| | - Xue Gong
- Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123, China
| | - Qingbo Xiao
- Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123, China
| | - Fujin Li
- Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123, China
| | - Deyang Ji
- Tianjin Key Laboratory of Molecular Optoelectronic Sciences, Department of Chemistry, Institute of Molecular Aggregation Science, Tianjin University, Tianjin 300072, China
| | - Xiaotao Zhang
- Tianjin Key Laboratory of Molecular Optoelectronic Sciences, Department of Chemistry, Institute of Molecular Aggregation Science, Tianjin University, Tianjin 300072, China
| | - Huanli Dong
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - Liqiang Li
- Tianjin Key Laboratory of Molecular Optoelectronic Sciences, Department of Chemistry, Institute of Molecular Aggregation Science, Tianjin University, Tianjin 300072, China.
- Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123, China
- Joint School of National University of Singapore and Tianjin University, International Campus of Tianjin University, Fuzhou 350207, China
| | - Wenping Hu
- Tianjin Key Laboratory of Molecular Optoelectronic Sciences, Department of Chemistry, Institute of Molecular Aggregation Science, Tianjin University, Tianjin 300072, China
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- Joint School of National University of Singapore and Tianjin University, International Campus of Tianjin University, Fuzhou 350207, China
| |
Collapse
|
9
|
Hansmann AK, Döring RC, Rinn A, Giesen SM, Fey M, Breuer T, Berger R, Witte G, Chatterjee S. Charge Transfer Excitation and Asymmetric Energy Transfer at the Interface of Pentacene-Perfluoropentacene Heterostacks. ACS APPLIED MATERIALS & INTERFACES 2021; 13:5284-5292. [PMID: 33492144 DOI: 10.1021/acsami.0c16172] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
High-performance solar cells demand efficient charge-carrier excitation, separation, and extraction. These requirements hold particularly true for molecular photovoltaics, where large exciton binding energies render charge separation challenging at their commonly complex donor-acceptor interface structure. Among others, charge-transfer (CT) states are considered to be important precursors for exciton dissociation and charge separation. However, the general nature of CT excitons and their formation pathways remain unclear. Layered quasiplanar crystalline molecular heterostructures of the prototypical donor-acceptor system pentacene-perfluoropentacene studied at cryogenic temperatures are a paramount model system to gain insights into the underlying physical mechanism. In particular, a detailed experiment-theory analysis on a layered heterojunction featuring perfluoropentacene in its π-stacked polymorph and pentacene in the Siegrist phase indicates that exciton diffusion in unitary films can influence the formation efficiency of CT excitons localized at internal interfaces for these conditions. The correlation of the structural characteristics, that is, the molecular arrangement at the interfaces, with their absorption and photoluminescence excitation spectra is consistent with exciton transfer from pentacene to the CT exciton state only, whereas no transfer of excitons from the perfluoropentacene is detected. Electronic structure calculations of the model systems and investigation of coupling matrix elements between the various electronic states involved suggest hampered exciton diffusion toward the internal interface in the perfluoropentacene films. The asymmetric energy landscape around an idealized internal donor-acceptor interface thus is identified as a reason for asymmetric energy transfer. Thus, long-range effects apparently can influence charge separation in crystalline molecular heterostructures, similar to band gap bowing, which is well established for inorganic pn-junctions.
Collapse
Affiliation(s)
- Anna-Katharina Hansmann
- Department of Chemistry, Philipps-University Marburg, Hans-Meerwein-Straße 4, Marburg D-35032, Germany
| | - Robin C Döring
- Institute of Experimental Physics I and Center for Materials Research (LaMa), Justus Liebig University Giessen, Heinrich-Buff-Ring 16, D-35392 Giessen, Germany
| | - Andre Rinn
- Institute of Experimental Physics I and Center for Materials Research (LaMa), Justus Liebig University Giessen, Heinrich-Buff-Ring 16, D-35392 Giessen, Germany
| | - Steffen M Giesen
- Department of Chemistry, Philipps-University Marburg, Hans-Meerwein-Straße 4, Marburg D-35032, Germany
| | - Melanie Fey
- Institute of Experimental Physics I and Center for Materials Research (LaMa), Justus Liebig University Giessen, Heinrich-Buff-Ring 16, D-35392 Giessen, Germany
| | - Tobias Breuer
- Department of Physics and Materials Sciences Center, Philipps-University Marburg, Renthof 7, Marburg D-35032, Germany
| | - Robert Berger
- Department of Chemistry, Philipps-University Marburg, Hans-Meerwein-Straße 4, Marburg D-35032, Germany
| | - Gregor Witte
- Department of Physics and Materials Sciences Center, Philipps-University Marburg, Renthof 7, Marburg D-35032, Germany
| | - Sangam Chatterjee
- Institute of Experimental Physics I and Center for Materials Research (LaMa), Justus Liebig University Giessen, Heinrich-Buff-Ring 16, D-35392 Giessen, Germany
| |
Collapse
|
10
|
Li P, Lu ZH. Interface Engineering in Organic Electronics: Energy‐Level Alignment and Charge Transport. SMALL SCIENCE 2020. [DOI: 10.1002/smsc.202000015] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Affiliation(s)
- Peicheng Li
- Department of Materials Science and Engineering University of Toronto Toronto M5S 3E4 Canada
| | - Zheng-Hong Lu
- Department of Materials Science and Engineering University of Toronto Toronto M5S 3E4 Canada
- Department of Physics Center for Optoelectronics Engineering Research Yunnan University Kunming 650091 P. R. China
| |
Collapse
|
11
|
Li T, Bandari VK, Hantusch M, Xin J, Kuhrt R, Ravishankar R, Xu L, Zhang J, Knupfer M, Zhu F, Yan D, Schmidt OG. Integrated molecular diode as 10 MHz half-wave rectifier based on an organic nanostructure heterojunction. Nat Commun 2020; 11:3592. [PMID: 32680989 PMCID: PMC7368027 DOI: 10.1038/s41467-020-17352-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Accepted: 06/23/2020] [Indexed: 11/23/2022] Open
Abstract
Considerable efforts have been made to realize nanoscale diodes based on single molecules or molecular ensembles for implementing the concept of molecular electronics. However, so far, functional molecular diodes have only been demonstrated in the very low alternating current frequency regime, which is partially due to their extremely low conductance and the poor degree of device integration. Here, we report about fully integrated rectifiers with microtubular soft-contacts, which are based on a molecularly thin organic heterojunction and are able to convert alternating current with a frequency of up to 10 MHz. The unidirectional current behavior of our devices originates mainly from the intrinsically different surfaces of the bottom planar and top microtubular Au electrodes while the excellent high frequency response benefits from the charge accumulation in the phthalocyanine molecular heterojunction, which not only improves the charge injection but also increases the carrier density. The demand for miniaturization of electronics has been motivating a growing interest in high-performance molecular electronics. Li, Bandari et al. report a fully integrated molecular rectifier based on a molecular heterojunction and microtubular electrode enabling high frequency operation at more than 10 MHz.
Collapse
Affiliation(s)
- Tianming Li
- Material Systems for Nanoelectronics, Chemnitz University of Technology, 09107, Chemnitz, Germany.,Institute for Integrative Nanosciences, Leibniz IFW Dresden, 01069, Dresden, Germany.,Center for Materials, Architectures and Integration of Nanomembranes (MAIN), Chemnitz University of Technology, 09126, Chemnitz, Germany
| | - Vineeth Kumar Bandari
- Material Systems for Nanoelectronics, Chemnitz University of Technology, 09107, Chemnitz, Germany.,Institute for Integrative Nanosciences, Leibniz IFW Dresden, 01069, Dresden, Germany.,Center for Materials, Architectures and Integration of Nanomembranes (MAIN), Chemnitz University of Technology, 09126, Chemnitz, Germany
| | - Martin Hantusch
- Institute for Solid State Research, Leibniz IFW Dresden, 01069, Dresden, Germany
| | - Jianhui Xin
- State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, 130022, China
| | - Robert Kuhrt
- Institute for Solid State Research, Leibniz IFW Dresden, 01069, Dresden, Germany
| | - Rachappa Ravishankar
- Material Systems for Nanoelectronics, Chemnitz University of Technology, 09107, Chemnitz, Germany.,Institute for Integrative Nanosciences, Leibniz IFW Dresden, 01069, Dresden, Germany
| | - Longqian Xu
- Material Systems for Nanoelectronics, Chemnitz University of Technology, 09107, Chemnitz, Germany.,Institute for Integrative Nanosciences, Leibniz IFW Dresden, 01069, Dresden, Germany
| | - Jidong Zhang
- State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, 130022, China
| | - Martin Knupfer
- Institute for Solid State Research, Leibniz IFW Dresden, 01069, Dresden, Germany
| | - Feng Zhu
- Material Systems for Nanoelectronics, Chemnitz University of Technology, 09107, Chemnitz, Germany. .,Institute for Integrative Nanosciences, Leibniz IFW Dresden, 01069, Dresden, Germany. .,Center for Materials, Architectures and Integration of Nanomembranes (MAIN), Chemnitz University of Technology, 09126, Chemnitz, Germany. .,State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, 130022, China.
| | - Donghang Yan
- State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, 130022, China
| | - Oliver G Schmidt
- Material Systems for Nanoelectronics, Chemnitz University of Technology, 09107, Chemnitz, Germany.,Institute for Integrative Nanosciences, Leibniz IFW Dresden, 01069, Dresden, Germany.,Center for Materials, Architectures and Integration of Nanomembranes (MAIN), Chemnitz University of Technology, 09126, Chemnitz, Germany
| |
Collapse
|
12
|
Franco-Cañellas A, Duhm S, Gerlach A, Schreiber F. Binding and electronic level alignment of π-conjugated systems on metals. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2020; 83:066501. [PMID: 32101802 DOI: 10.1088/1361-6633/ab7a42] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
We review the binding and energy level alignment of π-conjugated systems on metals, a field which during the last two decades has seen tremendous progress both in terms of experimental characterization as well as in the depth of theoretical understanding. Precise measurements of vertical adsorption distances and the electronic structure together with ab initio calculations have shown that most of the molecular systems have to be considered as intermediate cases between weak physisorption and strong chemisorption. In this regime, the subtle interplay of different effects such as covalent bonding, charge transfer, electrostatic and van der Waals interactions yields a complex situation with different adsorption mechanisms. In order to establish a better understanding of the binding and the electronic level alignment of π-conjugated molecules on metals, we provide an up-to-date overview of the literature, explain the fundamental concepts as well as the experimental techniques and discuss typical case studies. Thereby, we relate the geometric with the electronic structure in a consistent picture and cover the entire range from weak to strong coupling.
Collapse
Affiliation(s)
- Antoni Franco-Cañellas
- Institut für Angewandte Physik, Universität Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany
| | | | | | | |
Collapse
|
13
|
Akaike K. Distributions of Potential and Contact-Induced Charges in Conventional Organic Photovoltaics. MATERIALS (BASEL, SWITZERLAND) 2020; 13:E2411. [PMID: 32456312 PMCID: PMC7288283 DOI: 10.3390/ma13102411] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/25/2020] [Revised: 05/15/2020] [Accepted: 05/22/2020] [Indexed: 12/11/2022]
Abstract
The interfaces of dissimilar materials play central roles in photophysical events in organic photovoltaics (OPVs). Depth profiles of electrostatic potential and contact-induced charges determine the energy-level lineup of the frontier orbitals at electrode/organic and organic heterointerfaces. They are critical for the elementary processes in an OPV cell, such as generation and diffusion of free carriers. A simple electrostatic model describes the energetics in organic heterojunctions supported by an electrode, and experiments via photoelectron spectroscopy and the Kelvin probe method validate the potential distribution in the stacking direction of the device. A comparative study has clarified the significance of Fermi-level pinning and resulting electrostatic fields in determining the energy-level alignment. In this review, we discuss how parameters of device constituents affect the distributions of potential and the dark charges in conventional OPVs comprising metallophthalocyanine and C60 as donor and acceptor, respectively. The results of previous studies, together with additional numerical simulations, suggest that a number of the factors influence the depth profiles of the dark charge and potential, such as the work function of bottom materials, layer thickness, structural inhomogeneity at interfaces, top electrode, and stacking sequence.
Collapse
Affiliation(s)
- Kouki Akaike
- National Institute of Advanced Industrial Science and Technology, Tsukuba 305-8565, Japan
| |
Collapse
|
14
|
Sergi Lopes C, Merces L, de Oliveira RF, de Camargo DHS, Bof Bufon CC. Rectification ratio and direction controlled by temperature in copper phthalocyanine ensemble molecular diodes. NANOSCALE 2020; 12:10001-10009. [PMID: 32196026 DOI: 10.1039/c9nr10601d] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Organic diodes and molecular rectifiers are fundamental electronic devices that share one common feature: current rectification ability. Since both present distinct spatial dimensions and working principles, the rectification of organic diodes is usually achieved by interface engineering, while changes in molecular structures commonly control the molecular rectifiers' features. Here, we report on the first observation of temperature-driven inversion of the rectification direction (IRD) in ensemble molecular diodes (EMDs) prepared in a vertical stack configuration. The EMDs are composed of 20 nm thick molecular ensembles of copper phthalocyanine in close contact with one of its fluorinated derivatives. The material interface was found to be responsible for modifying the junction's conduction mechanisms from nearly activationless transport to Poole-Frenkel emission and phonon-assisted tunneling. In this context, the current rectification was found to be dependent on the interplay of such distinct charge transport mechanisms. The temperature has played a crucial role in each charge transport transition, which we have investigated via electrical measurements and band diagram analysis, thus providing the fundamentals on the IRD occurrence. Our findings represent an important step towards simple and rational control of rectification in carbon-based electronic nanodevices.
Collapse
Affiliation(s)
- Carolina Sergi Lopes
- Brazilian Nanotechnology National Laboratory (LNNano), Brazilian Center for Research in Energy and Materials (CNPEM), 13083-970, Campinas, São Paulo, Brazil
| | | | | | | | | |
Collapse
|
15
|
Kuhrt R, Hantusch M, Knupfer M, Büchner B. Charge transfer characteristics of F
6
TCNNQ–gold interface. SURF INTERFACE ANAL 2020. [DOI: 10.1002/sia.6794] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Robert Kuhrt
- IFF Leibniz Institute for Solid State and Materials Research (IFW) Dresden Germany
| | - Martin Hantusch
- IFF Leibniz Institute for Solid State and Materials Research (IFW) Dresden Germany
| | - Martin Knupfer
- IFF Leibniz Institute for Solid State and Materials Research (IFW) Dresden Germany
| | - Bernd Büchner
- IFF Leibniz Institute for Solid State and Materials Research (IFW) Dresden Germany
| |
Collapse
|
16
|
Wang Q, Franco-Cañellas A, Yang J, Hausch J, Struzek S, Chen M, Thakur PK, Gerlach A, Duhm S, Schreiber F. Heteromolecular Bilayers on a Weakly Interacting Substrate: Physisorptive Bonding and Molecular Distortions of Copper-Hexadecafluorophthalocyanine. ACS APPLIED MATERIALS & INTERFACES 2020; 12:14542-14551. [PMID: 32109044 DOI: 10.1021/acsami.9b22812] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Heteromolecular bilayers of π-conjugated organic molecules on metals, considered as model systems for more complex thin film heterostructures, are investigated with respect to their structural and electronic properties. By exploring the influence of the organic-metal interaction strength in bilayer systems, we determine the molecular arrangement in the physisorptive regime for copper-hexadecafluorophthalocyanine (F16CuPc) on Au(111) with intermediate layers of 5,7,12,14-pentacenetetrone and perylene-3,4,9,10-tetracarboxylic diimide. Using the X-ray standing wave technique to distinguish the different molecular layers, we show that these two bilayers are ordered following their deposition sequence. Surprisingly, F16CuPc as the second layer within the heterostructures exhibits an inverted intramolecular distortion compared to its monolayer structure.
Collapse
Affiliation(s)
- Qi Wang
- Institut für Angewandte Physik, Universität Tübingen, 72076 Tübingen, Germany
| | | | - Jiacheng Yang
- Institute of Functional Nano & Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices and Joint International Research Laboratory of Carbon-Based Functional Materials and Devices, Soochow University, Suzhou 215123, People's Republic of China
| | - Julian Hausch
- Institut für Angewandte Physik, Universität Tübingen, 72076 Tübingen, Germany
| | - Samuel Struzek
- Institut für Angewandte Physik, Universität Tübingen, 72076 Tübingen, Germany
| | - Mengting Chen
- Institute of Functional Nano & Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices and Joint International Research Laboratory of Carbon-Based Functional Materials and Devices, Soochow University, Suzhou 215123, People's Republic of China
| | - Pardeep Kumar Thakur
- Diamond Light Source, Harwell Science and Innovation Campus, Oxfordshire OX11 0DE, United Kingdom
| | - Alexander Gerlach
- Institut für Angewandte Physik, Universität Tübingen, 72076 Tübingen, Germany
| | - Steffen Duhm
- Institute of Functional Nano & Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices and Joint International Research Laboratory of Carbon-Based Functional Materials and Devices, Soochow University, Suzhou 215123, People's Republic of China
| | - Frank Schreiber
- Institut für Angewandte Physik, Universität Tübingen, 72076 Tübingen, Germany
| |
Collapse
|
17
|
Tan A, Zhang P. Tailoring the growth and electronic structures of organic molecular thin films. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:503001. [PMID: 31422957 DOI: 10.1088/1361-648x/ab3c22] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
In the rapidly developing electronics industry, it has become increasingly necessary to explore materials that are cheap, flexible and versatile which have led to significant research efforts towards organic molecular thin films. Organic molecules are unique compared to their inorganic atomic counterparts as their properties can be tuned drastically through chemical functionalization, offering versatility, though their extended shape and weak intermolecular interactions bring significant challenges to the control of both the growth and the electronic structures of molecular thin films. In this paper, we will review the self-assembly process and how to establish long-range ordered organic molecular thin films. We will also discuss how the electronic structures of thin films are impacted by the molecule's local electrostatic environment and its interaction with the substrate, within the context of controlling interfacial energy level alignment between organic semiconductors and electrodes in electronic devices.
Collapse
Affiliation(s)
- Andrew Tan
- Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824, United States of America
| | | |
Collapse
|
18
|
Band structure engineering in metal halide perovskite nanostructures for optoelectronic applications. NANO MATERIALS SCIENCE 2019. [DOI: 10.1016/j.nanoms.2019.10.004] [Citation(s) in RCA: 75] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
|
19
|
Kafle TR, Kattel B, Yao P, Zereshki P, Zhao H, Chan WL. Effect of the Interfacial Energy Landscape on Photoinduced Charge Generation at the ZnPc/MoS 2 Interface. J Am Chem Soc 2019; 141:11328-11336. [PMID: 31259543 DOI: 10.1021/jacs.9b05893] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Monolayer transition-metal dichalcogenide crystals (TMDC) can be combined with other functional materials, such as organic molecules, to form a wide range of heterostructures with tailorable properties. Although a number of works have shown that ultrafast charge transfer (CT) can occur at organic/TMDC interfaces, conditions that would facilitate the separation of interfacial CT excitons into free carriers remain unclear. Here, time-resolved and steady-state photoemission spectroscopy are used to study the potential energy landscape, charge transfer, and exciton dynamics at the zinc phthalocyanine (ZnPc)/monolayer (ML) MoS2 and ZnPc/bulk MoS2 interfaces. Surprisingly, although both interfaces have a type-II band alignment and exhibit sub-100 fs CT, the CT excitons formed at the two interfaces show drastically different evolution dynamics. The ZnPc/ML-MoS2 behaves like typical donor-acceptor interfaces in which CT excitons dissociate into electron-hole pairs. On the contrary, back electron transfer occur at ZnPc/bulk-MoS2, which results in the formation of triplet excitons in ZnPc. The difference can be explained by the different amount of band bending found in the ZnPc film deposited on ML-MoS2 and bulk-MoS2. Our work illustrates that the potential energy landscape near the interface plays an important role in the charge separation behavior. Therefore, considering the energy level alignment at the interface alone is not enough for predicting whether free charges can be generated effectively from an interface.
Collapse
Affiliation(s)
- Tika R Kafle
- Department of Physics and Astronomy , University of Kansas , Lawrence , Kansas 66045 , United States
| | - Bhupal Kattel
- Department of Physics and Astronomy , University of Kansas , Lawrence , Kansas 66045 , United States
| | - Peng Yao
- Department of Physics and Astronomy , University of Kansas , Lawrence , Kansas 66045 , United States.,Key Laboratory of Luminescence and Optical Information, Ministry of Education, Institute of Optoelectronic Technology , Beijing Jiaotong University , Beijing 100044 , China
| | - Peymon Zereshki
- Department of Physics and Astronomy , University of Kansas , Lawrence , Kansas 66045 , United States
| | - Hui Zhao
- Department of Physics and Astronomy , University of Kansas , Lawrence , Kansas 66045 , United States
| | - Wai-Lun Chan
- Department of Physics and Astronomy , University of Kansas , Lawrence , Kansas 66045 , United States
| |
Collapse
|
20
|
Futscher MH, Schultz T, Frisch J, Ralaiarisoa M, Metwalli E, Nardi MV, Müller-Buschbaum P, Koch N. Electronic properties of hybrid organic/inorganic semiconductor pn-junctions. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:064002. [PMID: 30523893 DOI: 10.1088/1361-648x/aaf310] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Hybrid inorganic/organic semiconductor heterojunctions are candidates to expand the scope of purely organic or inorganic junctions in electronic and optoelectronic devices. Comprehensive understanding of bulk and interface doping on the junction's electronic properties is therefore desirable. In this work, we elucidate the energy level alignment and its mechanisms at a prototypical hybrid pn-junction comprising ZnO (n-type) and p-doped N,N'-di(1-naphthyl)-N,N'-diphenyl-(1,1'-biphenyl)-4,4'-diamine (α-NPD) as semiconductors, using photoelectron spectroscopy. The level alignment can be quantitatively described by the interplay of contact-induced band and energy level bending in the inorganic and organic component away from the interface, and an interface dipole due to the push-back effect. By adjusting the dopant concentration in α-NPD, the position of the frontier energy levels of ZnO can be varied by over 0.5 eV and that of α-NPD by over 1 eV. The tunability of this pn-junction's energy levels evidences the substantial potential of the hybrid approach for enhancing device functionality.
Collapse
Affiliation(s)
- Moritz H Futscher
- Institut für Physik & IRIS Adlershof, Humboldt-Universität zu Berlin, 12489 Berlin, Germany. Physik-Department, Lehrstuhl für Funktionelle Materialien, Technische Universität München, 85748 Garching, Germany
| | | | | | | | | | | | | | | |
Collapse
|
21
|
Gusain A, Faria RM, Miranda PB. Polymer Solar Cells-Interfacial Processes Related to Performance Issues. Front Chem 2019; 7:61. [PMID: 30809519 PMCID: PMC6379278 DOI: 10.3389/fchem.2019.00061] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2018] [Accepted: 01/22/2019] [Indexed: 12/03/2022] Open
Abstract
Harnessing solar energy with solar cells based on organic materials (in particular polymeric solar cells) is an attractive alternative to silicon-based solar cells due to the advantages of lower weight, flexibility, lower manufacturing costs, easier integration with other products, low environmental impact during manufacturing and operations and short energy payback times. However, even with the latest efficiencies reported up to 17%, the reproducibility of these efficiencies is not up to par, with a significant variation in the efficiencies reported across the literature. Since these devices are based on ultrathin multilayer organic films, interfaces play a major role in their operation and performance. This review gives a concise account of the major interfacial issues that are responsible for influencing the device performance, with emphasis on their physical mechanisms. After an introduction to the basic principles of polymeric solar cells, it briefly discusses charge generation and recombination occurring at the donor-acceptor bulk heterojunction interface. It then discusses interfacial morphology for the active layer and how it affects the performance and stability of these devices. Next, the formation of injection and extraction barriers and their role in the device performance is discussed. Finally, it addresses the most common approaches to change these barriers for improving the solar cell efficiency, including the use of interface dipoles. These issues are interrelated to each other and give a clear and concise understanding of the problem of the underperformance due to interfacial phenomena occurring within the device. This review not only discusses some of the implemented approaches that have been adopted in order to address these problems, but also highlights interfacial issues that are yet to be fully understood in organic solar cells.
Collapse
Affiliation(s)
- Abhay Gusain
- Instituto de Física de São Carlos, Universidade de São Paulo, São Carlos, Brazil
| | - Roberto M Faria
- Instituto de Física de São Carlos, Universidade de São Paulo, São Carlos, Brazil
| | - Paulo B Miranda
- Instituto de Física de São Carlos, Universidade de São Paulo, São Carlos, Brazil
| |
Collapse
|
22
|
Kafle TR, Kattel B, Wang T, Chan WL. The relationship between the coherent size, binding energy and dissociation dynamics of charge transfer excitons at organic interfaces. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:454001. [PMID: 30265252 DOI: 10.1088/1361-648x/aae50b] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
At organic semiconductor interfaces, an electron and a hole can be bound Coulombically to form an interfacial charge transfer (CT) exciton. It is still under debate how a CT exciton can overcome its strong binding and dissociate into free carriers. Experimentally, capturing the evolution of the CT exciton on time (fs-ps) and length scales (nm) in which the dissociation process occurs is challenging. To overcome this challenge, time-resolved two photon photoemission spectroscopy is used to measure the binding energies and electronic coherent sizes of a series of CT states at organic interfaces, and capture the temporal dynamics of these CT excitons after their excitation. Using zinc phthalocyanine (ZnPc)/fullerene (C60) interface as a model system, it is shown that the interfacial CT process first populates a hot CT state with a coherent size of ~4 nm. Hot and delocalized CT excitons subsequently relax into CT excitons with lower energies and smaller coherent sizes. To correlate the CT exciton properties with the dissociation efficiency, we develop a method that exploits graphene field effect transistors to probe the rate and yield of free carrier generation at the interface. Our results show that exciton dissociation can be more efficient if one can extract electrons from the hot and delocalized CT state. We propose a cascade structure that would serve this purpose.
Collapse
Affiliation(s)
- Tika R Kafle
- Department of Physics and Astronomy, University of Kansas, Lawrence, KS 66045, United States of America
| | | | | | | |
Collapse
|
23
|
Lu SY, Mukhopadhyay S, Froese R, Zimmerman PM. Virtual Screening of Hole Transport, Electron Transport, and Host Layers for Effective OLED Design. J Chem Inf Model 2018; 58:2440-2449. [DOI: 10.1021/acs.jcim.8b00044] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Shao-Yu Lu
- Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States
| | | | - Robert Froese
- The Dow Chemical Company, Midland, Michigan 48674, United States
| | - Paul M. Zimmerman
- Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States
| |
Collapse
|
24
|
Izawa S, Shintaku N, Hiramoto M. Effect of Band Bending and Energy Level Alignment at the Donor/Acceptor Interface on Open-Circuit Voltage in Organic Solar Cells. J Phys Chem Lett 2018; 9:2914-2918. [PMID: 29770698 DOI: 10.1021/acs.jpclett.8b01134] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Open-circuit voltage ( VOC) is a key parameter governing the power conversion efficiency of organic solar cells. We clarified the effect of band bending in organic semiconductor films on the VOC of phthalocyanine (H2Pc)/fullerene (C60) planar heterojunction (PHJ) OSCs. The VOC was significantly affected by the H2Pc layer thickness, varying from 0.20 V at 2 nm to 0.49 V at 100 nm thickness. The large VOC change is due to the band bending in the H2Pc layer, where the difference in H2Pc layer thickness led to significant changes in the degree of the vacuum-level shift in the C60 layer because of the Fermi level ( EF) difference between the H2Pc and C60 layers. This result demonstrated that a new influential factor affecting the VOC is the position of the EF that is dependent on band bending in organic semiconductor films.
Collapse
Affiliation(s)
- Seiichiro Izawa
- Institute for Molecular Science , 5-1 Higashiyama, Myodaiji , Okazaki , Aichi 444-8787 , Japan
- The Graduate University for Advanced Studies (SOKENDAI) , 5-1 Higashiyama, Myodaiji , Okazaki , Aichi 444-8787 , Japan
| | - Naoto Shintaku
- Institute for Molecular Science , 5-1 Higashiyama, Myodaiji , Okazaki , Aichi 444-8787 , Japan
- The Graduate University for Advanced Studies (SOKENDAI) , 5-1 Higashiyama, Myodaiji , Okazaki , Aichi 444-8787 , Japan
| | - Masahiro Hiramoto
- Institute for Molecular Science , 5-1 Higashiyama, Myodaiji , Okazaki , Aichi 444-8787 , Japan
- The Graduate University for Advanced Studies (SOKENDAI) , 5-1 Higashiyama, Myodaiji , Okazaki , Aichi 444-8787 , Japan
| |
Collapse
|
25
|
Khim D, Luzio A, Bonacchini GE, Pace G, Lee MJ, Noh YY, Caironi M. Uniaxial Alignment of Conjugated Polymer Films for High-Performance Organic Field-Effect Transistors. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2018; 30:e1705463. [PMID: 29582485 DOI: 10.1002/adma.201705463] [Citation(s) in RCA: 66] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2017] [Revised: 12/28/2017] [Indexed: 06/08/2023]
Abstract
Polymer semiconductors have been experiencing a remarkable improvement in electronic and optoelectronic properties, which are largely related to the recent development of a vast library of high-performance, donor-acceptor copolymers showing alternation of chemical moieties with different electronic affinities along their backbones. Such steady improvement is making conjugated polymers even more appealing for large-area and flexible electronic applications, from distributed and portable electronics to healthcare devices, where cost-effective manufacturing, light weight, and ease of integration represent key benefits. Recently, a strong boost to charge carrier mobility in polymer-based field-effect transistors, consistently achieving the range from 1.0 to 10 cm2 V-1 s-1 for both holes and electrons, has been given by uniaxial backbone alignment of polymers in thin films, inducing strong transport anisotropy and favoring enhanced transport properties along the alignment direction. Herein, an overview on this topic is provided with a focus on the processing-structure-property relationships that enable the controlled and uniform alignment of polymer films over large areas with scalable processes. The key aspects are specific molecular structures, such as planarized backbones with a reduced degree of conformational disorder, solution formulation with controlled aggregation, and deposition techniques inducing suitable directional flow.
Collapse
Affiliation(s)
- Dongyoon Khim
- Department of Energy and Materials Engineering, Dongguk University, 30 Pildong-ro, 1-gil, Jung-gu, Seoul, 04620, Republic of Korea
| | - Alessandro Luzio
- Center for Nano Science and Technology @PoliMi, Istituto Italiano di Tecnologia, Via Pascoli 70/3, 20133, Milano, Italy
| | - Giorgio Ernesto Bonacchini
- Center for Nano Science and Technology @PoliMi, Istituto Italiano di Tecnologia, Via Pascoli 70/3, 20133, Milano, Italy
- Dipartimento di Fisica, Politecnico di Milano, P.zza L. da Vinci 32, 20133, Milan, Italy
| | - Giuseppina Pace
- Center for Nano Science and Technology @PoliMi, Istituto Italiano di Tecnologia, Via Pascoli 70/3, 20133, Milano, Italy
| | - Mi-Jung Lee
- School of Advanced Materials Engineering, Kookmin University, 77 Jeongneung-ro, Seongbuk-gu, Seoul, 136-712, Republic of Korea
| | - Yong-Young Noh
- Department of Energy and Materials Engineering, Dongguk University, 30 Pildong-ro, 1-gil, Jung-gu, Seoul, 04620, Republic of Korea
| | - Mario Caironi
- Center for Nano Science and Technology @PoliMi, Istituto Italiano di Tecnologia, Via Pascoli 70/3, 20133, Milano, Italy
| |
Collapse
|
26
|
Ibanez JG, Rincón ME, Gutierrez-Granados S, Chahma M, Jaramillo-Quintero OA, Frontana-Uribe BA. Conducting Polymers in the Fields of Energy, Environmental Remediation, and Chemical–Chiral Sensors. Chem Rev 2018; 118:4731-4816. [DOI: 10.1021/acs.chemrev.7b00482] [Citation(s) in RCA: 264] [Impact Index Per Article: 44.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Jorge G. Ibanez
- Departamento de Ingeniería y Ciencias Químicas, Universidad Iberoamericana, Prolongación Paseo de la Reforma 880, 01219 Ciudad de México, Mexico
| | - Marina. E. Rincón
- Instituto de Energías Renovables, Universidad Nacional Autónoma de México, Apartado Postal 34, 62580, Temixco, MOR, Mexico
| | - Silvia Gutierrez-Granados
- Departamento de Química, DCNyE, Campus Guanajuato, Universidad de Guanajuato, Cerro de la Venada S/N, Pueblito
de Rocha, 36080 Guanajuato, GTO Mexico
| | - M’hamed Chahma
- Laurentian University, Department of Chemistry & Biochemistry, Sudbury, ON P3E2C6, Canada
| | - Oscar A. Jaramillo-Quintero
- CONACYT-Instituto de Energías Renovables, Universidad Nacional Autónoma de México, Apartado Postal 34, 62580 Temixco, MOR, Mexico
| | - Bernardo A. Frontana-Uribe
- Centro Conjunto de Investigación en Química Sustentable, UAEM-UNAM, Km 14.5 Carretera Toluca-Ixtlahuaca, Toluca 50200, Estado de México Mexico
- Instituto de Química, Universidad Nacional Autónoma de México, Circuito
exterior Ciudad Universitaria, 04510 Ciudad de México, Mexico
| |
Collapse
|
27
|
Kotadiya NB, Lu H, Mondal A, Ie Y, Andrienko D, Blom PWM, Wetzelaer GJAH. Universal strategy for Ohmic hole injection into organic semiconductors with high ionization energies. NATURE MATERIALS 2018; 17:329-334. [PMID: 29459747 DOI: 10.1038/s41563-018-0022-8] [Citation(s) in RCA: 57] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2017] [Accepted: 01/15/2018] [Indexed: 06/08/2023]
Abstract
Barrier-free (Ohmic) contacts are a key requirement for efficient organic optoelectronic devices, such as organic light-emitting diodes, solar cells, and field-effect transistors. Here, we propose a simple and robust way of forming an Ohmic hole contact on organic semiconductors with a high ionization energy (IE). The injected hole current from high-work-function metal-oxide electrodes is improved by more than an order of magnitude by using an interlayer for which the sole requirement is that it has a higher IE than the organic semiconductor. Insertion of the interlayer results in electrostatic decoupling of the electrode from the semiconductor and realignment of the Fermi level with the IE of the organic semiconductor. The Ohmic-contact formation is illustrated for a number of material combinations and solves the problem of hole injection into organic semiconductors with a high IE of up to 6 eV.
Collapse
Affiliation(s)
| | - Hao Lu
- Max Planck Institute for Polymer Research, Mainz, Germany
| | - Anirban Mondal
- Max Planck Institute for Polymer Research, Mainz, Germany
| | - Yutaka Ie
- Max Planck Institute for Polymer Research, Mainz, Germany
- The Institute of Scientific and Industrial Research (ISIR), Osaka University, Ibaraki, Japan
| | | | - Paul W M Blom
- Max Planck Institute for Polymer Research, Mainz, Germany
| | | |
Collapse
|
28
|
Nakano K, Tajima K. Organic Planar Heterojunctions: From Models for Interfaces in Bulk Heterojunctions to High-Performance Solar Cells. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2017; 29:1603269. [PMID: 27885716 DOI: 10.1002/adma.201603269] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2016] [Revised: 08/30/2016] [Indexed: 05/28/2023]
Abstract
Recent progress regarding planar heterojunctions (PHJs) is reviewed, with respect to the fundamental understanding of the photophysical processes at the donor/acceptor interfaces in organic photovoltaic devices (OPVs). The current state of OPV research is summarized and the advantages of PHJs as models for exploring the relationship between organic interfaces and device characteristics described. The preparation methods and the characterization of PHJ structures to provide key points for the appropriate handling of PHJs. Next, we describe the effects of the donor/acceptor interface on each photoelectric conversion process are reviewed by examining various PHJ systems to clarify what is currently known and not known. Finally, it is discussed how we the knowledge obtained by studies of PHJs can be used to overcome the current limits of OPV efficiency.
Collapse
Affiliation(s)
- Kyohei Nakano
- RIKEN Center for Emergent Matter Science (CEMS), 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan
| | - Keisuke Tajima
- RIKEN Center for Emergent Matter Science (CEMS), 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan
- Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama, 332-0012, Japan
| |
Collapse
|
29
|
Li Y, Li P, Lu ZH. Mapping Energy Levels for Organic Heterojunctions. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2017; 29:1700414. [PMID: 28436573 DOI: 10.1002/adma.201700414] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2017] [Revised: 03/02/2017] [Indexed: 06/07/2023]
Abstract
An organic semiconductor thin film is a solid-state matter comprising one or more molecules. For applications in electronics and photonics, several distinct functional organic thin films are stacked together to create a variety of devices such as organic light-emitting diodes and organic solar cells. The energy levels at these thin-film junctions dictate various electronic processes such as the charge transport across these junctions, the exciton dissociation rates at donor-acceptor molecular interfaces, and the charge trapping during exciton formation in a host-dopant system. These electronic processes are vital to a device's performance and functionality. To uncover a general scientific principle in governing the interface energy levels, highest occupied molecular orbitals, and vacuum level dipoles, herein a comprehensive experimental research is conducted on several dozens of organic-organic heterojunctions representative of various device applications. It is found that the experimental data map on interface energy levels, after correcting variables such as molecular orientation-dependent ionization energies, consists of three distinct regions depending on interface fundamental physical parameters such as Fermi energy, work function, highest occupied molecular orbitals, and lowest unoccupied molecular orbitals. This general energy map provides a master guide in selection of new materials for fabricating future generations of organic semiconductor devices.
Collapse
Affiliation(s)
- Yiying Li
- Department of Materials Science and Engineering, University of Toronto, 184 College Street, Toronto, Ontario, M5S 3E4, Canada
| | - Peicheng Li
- Department of Materials Science and Engineering, University of Toronto, 184 College Street, Toronto, Ontario, M5S 3E4, Canada
| | - Zheng-Hong Lu
- Department of Materials Science and Engineering, University of Toronto, 184 College Street, Toronto, Ontario, M5S 3E4, Canada
- Department of Physics, Yunnan University, Yunnan, 650091, China
| |
Collapse
|
30
|
Röhr JA, Kirchartz T, Nelson J. On the correct interpretation of the low voltage regime in intrinsic single-carrier devices. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:205901. [PMID: 28294108 DOI: 10.1088/1361-648x/aa66cc] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
We discuss the approach of determining the charge-carrier density of a single-carrier device by combining Ohm's law and the Mott-Gurney law. We show that this approach is seldom valid, due to the fact that whenever Ohm's law is applicable the Mott-Gurney law is usually not, and vice versa. We do this using a numerical drift-diffusion solver to calculate the current density-voltage curves and the charge-carrier density, with increasing doping concentration. As this doping concentration is increased to very large values, using Ohm's law becomes a sensible way of measuring the product of mobility and doping density in the sample. However, in the high-doping limit, the current is no longer governed by space-charge and it will no longer be possible to determine the charge-carrier mobility using the Mott-Gurney law. This leaves the value for the mobility as an unknown in the mobility-doping density product in Ohm's law. We also show that, when the charge-carrier mobility for an intrinsic semiconductor is known in advance, the carrier density is underestimated up to many orders of magnitude if Ohm's law is used. We finally seek to establish a window of conditions where the two methods can be combined to yield reasonable results.
Collapse
Affiliation(s)
- Jason A Röhr
- Department of Physics and Centre for Plastic Electronics, Imperial College London, South Kensington Campus, London, SW7 2AZ, United Kingdom. Department of Chemistry and Centre for Plastic Electronics, Imperial College London, South Kensington Campus, London, SW7 2AZ, United Kingdom
| | | | | |
Collapse
|
31
|
Waas D, Rückerl F, Knupfer M, Büchner B. Energy-level alignment at interfaces between manganese phthalocyanine and C 60. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2017; 8:927-932. [PMID: 28546887 PMCID: PMC5433147 DOI: 10.3762/bjnano.8.94] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/23/2016] [Accepted: 03/22/2017] [Indexed: 06/07/2023]
Abstract
We have used photoelectron spectroscopy to determine the energy-level alignment at organic heterojunctions made of manganese phthalocyanine (MnPc) and the fullerene C60. We show that this energy-level alignment depends upon the preparation sequence, which is explained by different molecular orientations. Moreover, our results demonstrate that MnPc/C60 interfaces are hardly suited for application in organic photovoltaic devices, since the energy difference of the two lowest unoccupied molecular orbitals (LUMOs) is rather small.
Collapse
Affiliation(s)
- Daniel Waas
- IFW Dresden, P.O. Box 270116, D-01171 Dresden, Germany
| | | | | | - Bernd Büchner
- IFW Dresden, P.O. Box 270116, D-01171 Dresden, Germany
| |
Collapse
|
32
|
Opitz A. Energy level alignment at planar organic heterojunctions: influence of contact doping and molecular orientation. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:133001. [PMID: 28195076 DOI: 10.1088/1361-648x/aa5a6c] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Planar organic heterojunctions are widely used in photovoltaic cells, light-emitting diodes, and bilayer field-effect transistors. The energy level alignment in the devices plays an important role in obtaining the aspired gap arrangement. Additionally, the π-orbital overlap between the involved molecules defines e.g. the charge-separation efficiency in solar cells due to charge-transfer effects. To account for both aspects, direct/inverse photoemission spectroscopy and near edge x-ray absorption fine structure spectroscopy were used to determine the energy level landscape and the molecular orientation at prototypical planar organic heterojunctions. The combined experimental approach results in a comprehensive model for the electronic and morphological characteristics of the interface between the two investigated molecular semiconductors. Following an introduction on heterojunctions used in devices and on energy levels of organic materials, the energy level alignment of planar organic heterojunctions will be discussed. The observed energy landscape is always determined by the individual arrangement between the energy levels of the molecules and the work function of the electrode. This might result in contact doping due to Fermi level pinning at the electrode for donor/acceptor heterojunctions, which also improves the solar cell efficiency. This pinning behaviour can be observed across an unpinned interlayer and results in charge accumulation at the donor/acceptor interface, depending on the transport levels of the respective organic semiconductors. Moreover, molecular orientation will affect the energy levels because of the anisotropy in ionisation energy and electron affinity and is influenced by the structural compatibility of the involved molecules at the heterojunction. High structural compatibility leads to π-orbital stacking between different molecules at a heterojunction, which is of additional interest for photovoltaic active interfaces and for ground-state charge-transfer.
Collapse
|
33
|
D'Avino G, Muccioli L, Castet F, Poelking C, Andrienko D, Soos ZG, Cornil J, Beljonne D. Electrostatic phenomena in organic semiconductors: fundamentals and implications for photovoltaics. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2016; 28:433002. [PMID: 27603960 DOI: 10.1088/0953-8984/28/43/433002] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
This review summarizes the current understanding of electrostatic phenomena in ordered and disordered organic semiconductors, outlines numerical schemes developed for quantitative evaluation of electrostatic and induction contributions to ionization potentials and electron affinities of organic molecules in a solid state, and illustrates two applications of these techniques: interpretation of photoelectron spectroscopy of thin films and energetics of heterointerfaces in organic solar cells.
Collapse
Affiliation(s)
- Gabriele D'Avino
- Laboratory for the Chemistry of Novel Materials, Université de Mons, 7000 Mons, Belgium
| | | | | | | | | | | | | | | |
Collapse
|
34
|
Cao B, He X, Fetterly CR, Olsen BC, Luber EJ, Buriak JM. Role of Interfacial Layers in Organic Solar Cells: Energy Level Pinning versus Phase Segregation. ACS APPLIED MATERIALS & INTERFACES 2016; 8:18238-18248. [PMID: 27302178 DOI: 10.1021/acsami.6b02712] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
UNLABELLED Organic photovoltaics (OPVs) are assembled from a complex ensemble of layers of disparate materials, each playing a distinct role within the device. In this work, the role of the interface that bridges the transparent anode and the bulk heterojunction (BHJ) in an OPV device was investigated. The surface characteristics of the electrode interface affect the energy level alignment, phase segregation, and the local composition of the bulk heterojunction (BHJ), which is in close contact. The commonly used ITO/PEDOT:PSS electrode was tailored with a thin, low-band-gap polymer overlayer, called PBDTTPD-COOH, a variant of the established donor polymer, PBDTTPD. Three BHJs that were composed of a donor polymer and PC71BM, were examined, including the donor polymers PBDTTPD, PCDTBT, and PTB7, within the following OPV device stack: ITO/(interfacial layer or layers)/BHJ/LiF/Al/Mg. It was found that modification of the ITO/PEDOT:PSS electrode with PBDTTPD-COOH resulted in statistically significant increases of power conversion efficiency for the PBDTTPD- and PCDTBT-based donor polymer:PC71BM BHJs, but not for the PTB7:PC71BM BHJ. Ultraviolet photoelectron spectroscopy (UPS) enabled determination of the respective energy level diagrams for these three different polymers relative to the ITO/PEDOT:PSS/PBDTTPD-COOH electrode, and revealed no injection barrier in all three polymer/substrate pairs. The observed differences of efficiency were not, therefore, electronic in origin. ToF-SIMS depth profiling and detailed experiments to determine surface energies strongly suggested that the greatest factor influencing device performance was a significant change of the local composition of the BHJ at this interface. When favorable accumulation of the donor polymer at the PEDOT PSS/interfacial layer was observed, the result was higher OPV device efficiencies. These results suggest that for each BHJ, the surface energies of the electrodes need to be carefully considered, as they will influence the local composition of the BHJ and resulting device performance.
Collapse
Affiliation(s)
- Bing Cao
- Department of Chemistry, University of Alberta , 11227 Saskatchewan Drive, Edmonton, Alberta T6G 2G2, Canada
- National Institute for Nanotechnology, National Research Council Canada , 11421 Saskatchewan Drive, Edmonton, Alberta T6G 2M9, Canada
| | - Xiaoming He
- Department of Chemistry, University of Alberta , 11227 Saskatchewan Drive, Edmonton, Alberta T6G 2G2, Canada
| | - Christopher R Fetterly
- Department of Chemistry, University of Alberta , 11227 Saskatchewan Drive, Edmonton, Alberta T6G 2G2, Canada
- National Institute for Nanotechnology, National Research Council Canada , 11421 Saskatchewan Drive, Edmonton, Alberta T6G 2M9, Canada
| | - Brian C Olsen
- Department of Chemistry, University of Alberta , 11227 Saskatchewan Drive, Edmonton, Alberta T6G 2G2, Canada
- National Institute for Nanotechnology, National Research Council Canada , 11421 Saskatchewan Drive, Edmonton, Alberta T6G 2M9, Canada
| | - Erik J Luber
- Department of Chemistry, University of Alberta , 11227 Saskatchewan Drive, Edmonton, Alberta T6G 2G2, Canada
- National Institute for Nanotechnology, National Research Council Canada , 11421 Saskatchewan Drive, Edmonton, Alberta T6G 2M9, Canada
| | - Jillian M Buriak
- Department of Chemistry, University of Alberta , 11227 Saskatchewan Drive, Edmonton, Alberta T6G 2G2, Canada
- National Institute for Nanotechnology, National Research Council Canada , 11421 Saskatchewan Drive, Edmonton, Alberta T6G 2M9, Canada
| |
Collapse
|
35
|
Zou Y, Mao H, Meng Q, Zhu D. Impact of MoO3 interlayer on the energy level alignment of pentacene-C60 heterostructure. J Chem Phys 2016; 144:084706. [DOI: 10.1063/1.4942480] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Ye Zou
- Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - Hongying Mao
- Department of Physics, Hangzhou Normal University, Hangzhou 310036, China
- State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, China
| | - Qing Meng
- Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - Daoben Zhu
- Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| |
Collapse
|
36
|
Organic heterojunctions: Contact-induced molecular reorientation, interface states, and charge re-distribution. Sci Rep 2016; 6:21291. [PMID: 26887445 PMCID: PMC4758050 DOI: 10.1038/srep21291] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2015] [Accepted: 01/21/2016] [Indexed: 11/08/2022] Open
Abstract
We reveal the rather complex interplay of contact-induced re-orientation and interfacial electronic structure - in the presence of Fermi-level pinning - at prototypical molecular heterojunctions comprising copper phthalocyanine (H16CuPc) and its perfluorinated analogue (F16CuPc), by employing ultraviolet photoelectron and X-ray absorption spectroscopy. For both layer sequences, we find that Fermi-level (EF) pinning of the first layer on the conductive polymer substrate modifies the work function encountered by the second layer such that it also becomes EF-pinned, however, at the interface towards the first molecular layer. This results in a charge transfer accompanied by a sheet charge density at the organic/organic interface. While molecules in the bulk of the films exhibit upright orientation, contact formation at the heterojunction results in an interfacial bilayer with lying and co-facial orientation. This interfacial layer is not EF-pinned, but provides for an additional density of states at the interface that is not present in the bulk. With reliable knowledge of the organic heterojunction's electronic structure we can explain the poor performance of these in photovoltaic cells as well as their valuable function as charge generation layer in electronic devices.
Collapse
|