1
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Li J, Ji Q, Wang R, Zhang ZG, Wang X, Xiao M, Lu YQ, Zhang C. Charge Generation Dynamics in Organic Photovoltaic Blends under One-Sun-Equivalent Illumination Detected by Highly Sensitive Terahertz Spectroscopy. J Am Chem Soc 2024. [PMID: 38980945 DOI: 10.1021/jacs.4c05786] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/11/2024]
Abstract
Organic photovoltaic (OPV) devices attain high performance with nonfullerene acceptors by utilizing the synergistic dual channels of charge generation that originate from excitations in both the donor and acceptor materials. However, the specific intermediate states that facilitate both channels are subject to debate. To address this issue, we employ time-resolved terahertz spectroscopy with improved sensitivity (ΔE/E < 10-6), enabling direct probing of charge generation dynamics in a prototypical PM6:Y6 bulk heterojunction system under one-sun-equivalent excitation density. Charge generation arising from donor excitations is characterized with a rise time of ∼9 ps, while that from acceptor excitations shows a rise time of ∼18 ps. Temperature-dependent measurements further reveal notably distinct activation energies for these two charge generation pathways. Additionally, the two channels of charge generation can be substantially manipulated by altering the ratio of bulk to interfaces. These findings strongly suggest the presence of two distinct intermediate states: interfacial and intramoiety excitations. These states are crucial in mediating the transfer of electrons and holes, driving charge generation within OPV devices.
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Affiliation(s)
- Jiacong Li
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center for Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Qing Ji
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center for Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Rui Wang
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center for Advanced Microstructures, Nanjing University, Nanjing 210093, China
- College of Physics, Nanjing University of Aeronautics and Astronautics, and Key Laboratory of Aerospace Information Materials and Physics (NUAA), MIIT, Nanjing 211106, China
- Institute of Materials Engineering, Nanjing University, Nantong, Jiangsu 226019, China
| | - Zhi-Guo Zhang
- State Key Laboratory of Organic/Inorganic Composites, Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, China
| | - Xiaoyong Wang
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center for Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Min Xiao
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center for Advanced Microstructures, Nanjing University, Nanjing 210093, China
- Department of Physics, University of Arkansas, Fayetteville, Arkansas 72701, United States
| | - Yan-Qing Lu
- National Laboratory of Solid State Microstructures, Key Laboratory of Intelligent Optical Sensing and Manipulation, College of Engineering and Applied Sciences, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210023, China
| | - Chunfeng Zhang
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center for Advanced Microstructures, Nanjing University, Nanjing 210093, China
- Institute of Materials Engineering, Nanjing University, Nantong, Jiangsu 226019, China
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2
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Li S, Nishikubo R, Saeki A. Combined Charge Extraction by Linearly Increasing Voltage and Time-Resolved Microwave Conductivity to Reveal the Dynamic Charge Carrier Mobilities in Thin-Film Organic Solar Cells. ACS OMEGA 2024; 9:26951-26962. [PMID: 38947799 PMCID: PMC11209900 DOI: 10.1021/acsomega.3c09977] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/13/2023] [Revised: 05/22/2024] [Accepted: 06/05/2024] [Indexed: 07/02/2024]
Abstract
This article reports a purely experiment-based method to evaluate the time-dependent charge carrier mobilities in thin-film organic solar cells (OSCs) using simultaneous charge extraction by linearly increasing the voltage (CELIV) and time-resolved microwave conductivity (TRMC) measurements. This method enables the separate measurement of electron mobility (μe) and hole mobility (μh) in a metal-insulator-semiconductor (MIS) device. A slope-injection-restoration voltage profile for MIS-CELIV is also proposed to accurately determine the charge densities. The dynamic behavior of μe and μh is examined in five bulk heterojunction (BHJ) OSCs of polymer:fullerene (P3HT:PCBM and PffBT4T:PCBM) and polymer:nonfullerene acceptor (PM6:ITIC, PM6:IT4F, and PM6:Y6). While the former exhibits fast decays of μh and μe, the latter, in particular, PM6:IT4F and PM6:Y6, exhibits slow decays. Notably, the high-performing PM6:Y6 demonstrates both a balanced mobility (μe/μh) of 1.0-1.1 within 30 μs and relatively large CELIV-TRMC mobility values among the five BHJs. The results exhibit reasonable consistency with a high fill factor. The proposed new CELIV-TRMC technique offers a path toward a comprehensive understanding of dynamic mobility and its correlation with the OSC performance.
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Affiliation(s)
- Shaoxian Li
- Department
of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Ryosuke Nishikubo
- Department
of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
- Innovative
Catalysis Science Division (ICS), Institute for Open and Transdisciplinary
Research Initiatives (OTRI), Osaka University, 1-1 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Akinori Saeki
- Department
of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
- Innovative
Catalysis Science Division (ICS), Institute for Open and Transdisciplinary
Research Initiatives (OTRI), Osaka University, 1-1 Yamadaoka, Suita, Osaka 565-0871, Japan
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3
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Mizuno Y, Nogata A, Suzuki M, Nakayama KI, Hisaki I, Kishi R, Konishi A, Yasuda M. Synthesis and Characterization of Dibenzothieno[ a, f]pentalenes Enabling Large Antiaromaticity and Moderate Open-Shell Character through a Small Energy Barrier for Bond-Shift Valence Tautomerization. J Am Chem Soc 2023; 145:20595-20609. [PMID: 37695346 DOI: 10.1021/jacs.3c07356] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/12/2023]
Abstract
Experimental and theoretical rationalization of bond-shift valence tautomerization, characterized by double-well potential surfaces, is one of the most challenging topics of study among the rich electronic properties of antiaromatic molecules. Although the pseudo-Jahn-Teller effect (PJTE) is an essential effect to provide attractive characteristics of 4nπ systems, an understanding of the structure-property relationship derived from the PJTE for planar 4nπ electron systems is still in its infancy. Herein, we describe the synthesis and characterization of two regioisomers of the thiophene-fused diareno[a,f]pentalenes 6 and 7. The magnetic and optoelectronic properties characterize these sulfur-doped diareno[a,f]pentalenes as open-shell antiaromatic molecules, in sharp contrast to the closed-shell antiaromatic systems of 3 and 5, in which these main cores consist of the same number of π electrons as 6 and 7. Notably, thiophene-fused 6b and 7b showed pronounced antiaromaticity, the strongest among the previous systems, as well as moderate open-shell characteristics. Our experimental and theoretical investigations concluded that these properties of 6b and 7b are derived from the small energy barrier Ea‡ for the bond-shift valence tautomerization. The energy profile of the single crystal of 6b showed the temperature-dependent structural variations assigned to the dynamic mutual exchange between the two Cs-symmetric structures, which was also supported by changes in the chemical shifts of variable-temperature 1H NMR spectra in the solution phase. Both experimental and computational results revealed the importance of introducing heteroaromatic rings into 4nπ systems for controlling the PJTE and manifesting the antiaromatic and open-shell natures originating from the high-symmetric structure. The findings of this study advance the understanding of antiaromaticity characterized by the PJTE by controlling the energy barrier for bond-shift valence tautomerizations, potentially leading to the rational design of optoelectronic devices based on novel antiaromatic molecules possessing the strong contributions of their high-symmetric geometries.
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Affiliation(s)
- Yusuke Mizuno
- Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Akira Nogata
- Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Mitsuharu Suzuki
- Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Ken-Ichi Nakayama
- Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Ichiro Hisaki
- Division of Chemistry, Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531, Japan
| | - Ryohei Kishi
- Department of Materials Engineering Science, Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531, Japan
- Center for Quantum Information and Quantum Biology (QIQB), Osaka University, Toyonaka, Osaka 560-8531, Japan
- Innovative Catalysis Science Division, Institute for Open and Transdisciplinary Research Initiatives (ICS-OTRI), Osaka University, Suita, Osaka 565-0871, Japan
| | - Akihito Konishi
- Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
- Innovative Catalysis Science Division, Institute for Open and Transdisciplinary Research Initiatives (ICS-OTRI), Osaka University, Suita, Osaka 565-0871, Japan
| | - Makoto Yasuda
- Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
- Innovative Catalysis Science Division, Institute for Open and Transdisciplinary Research Initiatives (ICS-OTRI), Osaka University, Suita, Osaka 565-0871, Japan
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4
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Willson JT, Liu W, Balzer D, Kassal I. Jumping Kinetic Monte Carlo: Fast and Accurate Simulations of Partially Delocalized Charge Transport in Organic Semiconductors. J Phys Chem Lett 2023; 14:3757-3764. [PMID: 37044057 DOI: 10.1021/acs.jpclett.3c00388] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
Developing devices using disordered organic semiconductors requires accurate and practical models of charge transport. In these materials, charge transport occurs through partially delocalized states in an intermediate regime between localized hopping and delocalized band conduction. Partial delocalization can increase mobilities by orders of magnitude compared to those with conventional hopping, making it important for the design of materials and devices. Although delocalization, disorder, and polaron formation can be described using delocalized kinetic Monte Carlo (dKMC), it is a computationally expensive method. Here, we develop jumping kinetic Monte Carlo (jKMC), a model that approaches the accuracy of dKMC for modest amounts of delocalization (such as those found in disordered organic semiconductors), with a computational cost comparable to that of conventional hopping. jKMC achieves its computational performance by modeling conduction using identical spherical polarons, yielding a simple delocalization correction to the Marcus hopping rate that allows polarons to jump over their nearest neighbors. jKMC can be used in regimes of partial delocalization inaccessible to dKMC to show that modest delocalization can increase mobilities by as much as 2 orders of magnitude.
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Affiliation(s)
- Jacob T Willson
- School of Chemistry, University of Sydney, Sydney, NSW 2006, Australia
| | - William Liu
- School of Chemistry, University of Sydney, Sydney, NSW 2006, Australia
| | - Daniel Balzer
- School of Chemistry, University of Sydney, Sydney, NSW 2006, Australia
| | - Ivan Kassal
- School of Chemistry, University of Sydney, Sydney, NSW 2006, Australia
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5
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Unraveling complex performance-limiting factors of brominated ITIC derivative: PM6 organic solar cells by using time-resolved measurements. Polym J 2022. [DOI: 10.1038/s41428-022-00704-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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6
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Novikov S. Charge transport in the spatially correlated exponential random energy landscape: effect of the nonpositive correlation function. Phys Chem Chem Phys 2022; 24:9534-9542. [PMID: 35389389 DOI: 10.1039/d1cp04991g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Charge transport in amorphous semiconductors having spatially correlated exponential density of states (DOS) has been considered for the arbitrary behavior of the correlation function of random energies. Average carrier velocity is exactly calculated for the quasi-equilibrium (nondispersive) transport regime. For the symmetric exponential DOS with exponential tails for low and high energies and nonpositive correlation function the temperature of the transition to the dispersive transport regime depends on correlation properties and becomes greater than the traditional estimation based on the DOS decay energy kT = U0. Another new feature of the transport in the landscape having nonpositive correlation function is the decrease of the mobility with the field in the low field region and development of the universal mobility field dependence for stronger fields.
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Affiliation(s)
- Sergey Novikov
- A.N. Frumkin Institute of Physical Chemistry and Electrochemistry, Leninsky Prosp. 31, Moscow 119071, Russia.
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7
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Horii K, Nogata A, Mizuno Y, Iwasa H, Suzuki M, Nakayama KI, Konishi A, Yasuda M. Synthesis and Characterization of Dinaphtho[2,1-a:2,3-f]pentalene: A Stable Antiaromatic/Quinoidal Hydrocarbon Showing Appropriate Carrier Mobility in the Amorphous Layer. CHEM LETT 2022. [DOI: 10.1246/cl.210809] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Koki Horii
- Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Akira Nogata
- Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Yusuke Mizuno
- Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Haruna Iwasa
- Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Mitsuharu Suzuki
- Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Ken-ichi Nakayama
- Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Akihito Konishi
- Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
- Center for Atomic and Molecular Technologies, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
- Innovative Catalysis Science Division, Institute for Open and Transdisciplinary Research Initiatives (ICS-OTRI), Osaka University, Suita, Osaka 565-0871, Japan
| | - Makoto Yasuda
- Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
- Innovative Catalysis Science Division, Institute for Open and Transdisciplinary Research Initiatives (ICS-OTRI), Osaka University, Suita, Osaka 565-0871, Japan
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8
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Wu J, Cha H, Du T, Dong Y, Xu W, Lin CT, Durrant JR. A Comparison of Charge Carrier Dynamics in Organic and Perovskite Solar Cells. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2022; 34:e2101833. [PMID: 34773315 DOI: 10.1002/adma.202101833] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Revised: 09/10/2021] [Indexed: 06/13/2023]
Abstract
The charge carrier dynamics in organic solar cells and organic-inorganic hybrid metal halide perovskite solar cells, two leading technologies in thin-film photovoltaics, are compared. The similarities and differences in charge generation, charge separation, charge transport, charge collection, and charge recombination in these two technologies are discussed, linking these back to the intrinsic material properties of organic and perovskite semiconductors, and how these factors impact on photovoltaic device performance is elucidated. In particular, the impact of exciton binding energy, charge transfer states, bimolecular recombination, charge carrier transport, sub-bandgap tail states, and surface recombination is evaluated, and the lessons learned from transient optical and optoelectronic measurements are discussed. This perspective thus highlights the key factors limiting device performance and rationalizes similarities and differences in design requirements between organic and perovskite solar cells.
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Affiliation(s)
- Jiaying Wu
- Department of Chemistry and Centre for Processable Electronics, Imperial College London, London, W12 0BZ, UK
| | - Hyojung Cha
- Department of Chemistry and Centre for Processable Electronics, Imperial College London, London, W12 0BZ, UK
- Department of Hydrogen & Renewable Energy, Kyungpook National University, Daegu, 41566, South Korea
| | - Tian Du
- Department of Chemistry and Centre for Processable Electronics, Imperial College London, London, W12 0BZ, UK
| | - Yifan Dong
- Department of Chemistry and Centre for Processable Electronics, Imperial College London, London, W12 0BZ, UK
| | - Weidong Xu
- Department of Chemistry and Centre for Processable Electronics, Imperial College London, London, W12 0BZ, UK
| | - Chieh-Ting Lin
- Department of Chemistry and Centre for Processable Electronics, Imperial College London, London, W12 0BZ, UK
| | - James R Durrant
- Department of Chemistry and Centre for Processable Electronics, Imperial College London, London, W12 0BZ, UK
- SPECIFIC IKC, College of Engineering, Swansea University, Bay Campus, Fabian Way, Swansea, Wales, SA1 8EN, UK
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9
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Charge Carriers Density, Temperature, and Electric Field Dependence of the Charge Carrier Mobility in Disordered Organic Semiconductors in Low Density Region. CONDENSED MATTER 2021. [DOI: 10.3390/condmat6040038] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
We investigate the transport properties of charge carriers in disordered organic semiconductors using a model that relates a mobility with charge carriers (not with small polarons) hopping by thermal activation. Considering Miller and Abrahams expression for a hopping rate of a charge carrier between localized states of a Gaussian distributed energies, we employ Monte Carlo simulation methods, and calculate the average mobility of finite charge carriers focusing on a lower density region where the mobility was shown experimentally to be independent of the density. There are Monte Carlo simulation results for density dependence of mobility reported for hopping on regularly spaced states neglecting the role of spatial disorder, which does not fully mimic the hopping of charge carriers on randomly distributed states in disordered system as shown in recent publications. In this work we include the spatial disorder and distinguish the effects of electric field and density which are not separable in the experiment, and investigate the influence of density and electric field on mobility at different temperatures comparing with experimental results and that found in the absence of the spatial disorder. Moreover, we analyze the role of density and localization length on temperature and electric field dependence of mobility. Our results also give additional insight regarding the value of localization length that has been widely used as 0.1b where b is a lattice sites spacing.
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10
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Hamada F, Saeki A. Mobility Relaxation of Holes and Electrons in Polymer:Fullerene and Polymer : Non-Fullerene Acceptor Solar Cells. CHEMSUSCHEM 2021; 14:3528-3534. [PMID: 33847041 DOI: 10.1002/cssc.202100566] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2021] [Revised: 04/09/2021] [Indexed: 06/12/2023]
Abstract
A non-fullerene small molecular acceptor (NFA) is a prominent molecule that shows moderate electron mobility and a narrow bandgap complementary to middle-bandgap p-type conjugated polymers, which leads to great improvement in the performance of organic photovoltaic (OPV) cells. However, little is known about the relaxation of charge carriers, which is key to efficient charge transport. Simultaneous time-of-flight (TOF) and time-resolved microwave conductivity (TRMC) measurements have been carried out on benzodithiophene-based polymer (PBDB-T):soluble C70 -fullerere (PCBM) and PBDB-T:NFA (ITIC or Y6) blends, as benchmark systems. In addition to the conventional TOF mobilities, relaxation of the hole and electron mobility are evaluated by TRMC under an external electric field. PBDB-T : ITIC exhibits much faster relaxation than PBDB-T : PCBM, whereas that in PBDB-T : Y6 is moderate. This is consistent with the energetic disorder estimated from the photoabsorption onset. Interestingly, the slower relaxation of the electrons compared to the holes in PBDB-T : Y6 is in line with the preferred normal device structure. Our work deepens the understanding of the energetics of polymer : NFA blends and offers a basis for achieving efficient NFA properties.
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Affiliation(s)
- Fumiya Hamada
- Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Akinori Saeki
- Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka, 565-0871, Japan
- Innovative Catalysis Science Division, Institute for Open and Transdisciplinary Research Initiatives (ICS-OTRI), Osaka University, 2-1 Yamadaoka, Suita, Osaka, 565-0871, Japan
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11
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Novikov S. Two-dimensional bimolecular recombination in amorphous organic semiconductors. Phys Chem Chem Phys 2020; 22:1174-1180. [PMID: 31848542 DOI: 10.1039/c9cp05511h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We consider the two-dimensional bimolecular recombination of charge carriers in amorphous organic semiconductors having the lamellar structure. We calculate the dependence of the effective recombination rate constant on the carrier density taking into account the correlated nature of the energetic disorder typical for organic semiconductors. The resulting recombination kinetics demonstrates a very rich variety of behaviors depending on the correlation properties of the particular semiconductor and relevant charge density range.
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Affiliation(s)
- Sergey Novikov
- A.N. Frumkin Institute of Physical Chemistry and Electrochemistry, Leninsky prosp. 31, Moscow 119071, Russia. and National Research University Higher School of Economics, Myasnitskaya Ulitsa 20, Moscow 101000, Russia
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12
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Athanasopoulos S, Bässler H, Köhler A. Disorder vs Delocalization: Which Is More Advantageous for High-Efficiency Organic Solar Cells? J Phys Chem Lett 2019; 10:7107-7112. [PMID: 31661274 DOI: 10.1021/acs.jpclett.9b02866] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
We investigate the combined influence of energetic disorder and delocalization on electron-hole charge-transfer state separation efficiency in donor-acceptor organic photovoltaic systems using an analytical hopping model and Monte Carlo calculations, coupled with an effective mass model. Whereas energetic disorder increases the separation yield at intermediate and low electric fields for low-efficiency blends with strongly localized carriers, we find that it reduces dramatically the fill factors and power conversion efficiencies in high-efficiency solar cells that require high carrier delocalization within the conjugated segment and high mobility-lifetime product. We further demonstrate that the initial electron-hole distance and thermalization processes play only a minor role in the separation dynamics.
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Affiliation(s)
- Stavros Athanasopoulos
- Departamento de Física , Universidad Carlos III de Madrid , Avenida Universidad 30 , 28911 Leganés, Madrid , Spain
| | - Heinz Bässler
- Bayreuth Institute of Macromolecular Research (BIMF) and Bavarian Polymer Institute (BPI) , University of Bayreuth , Bayreuth 95440 , Germany
| | - Anna Köhler
- Bayreuth Institute of Macromolecular Research (BIMF) and Bavarian Polymer Institute (BPI) , University of Bayreuth , Bayreuth 95440 , Germany
- Soft Matter Optoelectronics , University of Bayreuth , Bayreuth 95440 , Germany
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13
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Rudnicki PE, MacPherson Q, Balhorn L, Feng B, Qin J, Salleo A, Spakowitz AJ. Impact of Liquid-Crystalline Chain Alignment on Charge Transport in Conducting Polymers. Macromolecules 2019. [DOI: 10.1021/acs.macromol.9b01729] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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14
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Electric polarization of electron-hole pairs in organic semiconductors induced by picosecond pulses of an electromagnetic wave: Consideration of small-molecule semiconductors with a negligibly small concentration of traps. Chem Phys 2019. [DOI: 10.1016/j.chemphys.2019.110456] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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15
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Kaiser W, Gagliardi A. Kinetic Monte Carlo Study of the Role of the Energetic Disorder on the Open-Circuit Voltage in Polymer/Fullerene Solar Cells. J Phys Chem Lett 2019; 10:6097-6104. [PMID: 31533434 DOI: 10.1021/acs.jpclett.9b02144] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
One major factor limiting the efficiency in organic solar cells (OSCs) is the low open-circuit voltage (Voc). Existing theoretical studies link the Voc with the charge transfer (CT) state and nonradiative recombination. However, also morphology and energetic disorder can have a strong impact on the Voc within realistic bulk-heterojunction OSCs. In this work, we present a kinetic Monte Carlo study on the role of the energetic disorder on the maximum Voc. We compute the quasi-Fermi level splitting for different energetic disorder and analyze the impact of the energetic disorder at the donor-acceptor interface as well as correlations in the site energies on the Voc. Our results show that the interface strongly controls the maximum Voc. For a higher interface disorder, charge densities and nongeminate recombination increase and the Voc is reduced. Furthermore, the correlated morphologies show an increase in the maximum Voc and a reduced impact of the energetic disorder.
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Affiliation(s)
- W Kaiser
- Department of Electrical and Computer Engineering , Technical University of Munich , Karlstraße 45 , 80333 Munich , Germany
| | - A Gagliardi
- Department of Electrical and Computer Engineering , Technical University of Munich , Karlstraße 45 , 80333 Munich , Germany
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