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Irshad Z, Lee W, Adnan M, Choi Y, Park T, Lim J. Elucidating Charge Carrier Dynamics in Perovskite-Based Tandem Solar Cells. Small Methods 2024; 8:e2300238. [PMID: 37322273 DOI: 10.1002/smtd.202300238] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2023] [Revised: 05/26/2023] [Indexed: 06/17/2023]
Abstract
Recently, multijunction tandem solar cells (TSCs) have presented high power conversion efficiency and revealed their immense potential in photovoltaic evolution. It is demonstrated that multiple light absorbers with various bandgap energies overcome the Shockley-Queisser limit of single-junction solar cells by absorbing the wide-range wavelength photons. Here, the main key challenges are reviewed, especially the charge carrier dynamics in perovskite-based 2-terminal (2-T) TSCs in terms of current matching, and how to manage these issues from a vantage point of characterization. To do this, the effect of recombination layers, optical and fabrication hurdles, and the impact of wide bandgap perovskite solar cells are discussed extensively. Afterward, this review focuses on various optoelectronics, spectroscopic, and theoretical (optical simulation) characterizations to figure out those issues, especially current-matching issues faced by the photovoltaic society. This review comprehensively provides deep insights into the relationship between the current-matching problems and the photovoltaic performance of TSCs through a variety of perspectives. Consequently, it is believed that this review is essential to address the main problems of 2-T TSCs, and the suggestions to elucidate the charge carrier dynamics and its characterization may pave the way to overcome such obstacles to further improve the development of 2-T TSCs in relation to the current-matching problems.
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Affiliation(s)
- Zobia Irshad
- Graduate School of Energy Science and Technology, Chungnam National University, Daejeon, 34134, Republic of Korea
| | - Wonjong Lee
- Graduate School of Energy Science and Technology, Chungnam National University, Daejeon, 34134, Republic of Korea
| | - Muhammad Adnan
- Graduate School of Energy Science and Technology, Chungnam National University, Daejeon, 34134, Republic of Korea
| | - Yelim Choi
- Department of Chemical Engineering, Pohang University of Science and Technology, Pohang, 37673, Republic of Korea
| | - Taiho Park
- Department of Chemical Engineering, Pohang University of Science and Technology, Pohang, 37673, Republic of Korea
| | - Jongchul Lim
- Graduate School of Energy Science and Technology, Chungnam National University, Daejeon, 34134, Republic of Korea
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Feng L, Li Z, Liu Y, Hua L, Wei Z, Cheng Y, Zhang Z, Xu B. Counterion Engineering toward High-Performance and pH-Neutral Polyoxometalates-Based Hole-Transporting Materials for Efficient Organic Optoelectronic Devices. ACS Nano 2024; 18:3276-3285. [PMID: 38252155 DOI: 10.1021/acsnano.3c09865] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2024]
Abstract
Although protonated polyoxometalates (POMs) are promising hole-transporting layer (HTL) materials for optoelectronic devices owing to their excellent hole collection/injection property, pH neutrality, and noncorrosiveness, POMs are seldom used as high-performance HTL materials. Herein, we designed and synthesized a series of mixed-additive POMs with pH-neutral counterions (NH4+, K+, and Na+) as HTL materials. X-ray photoelectron spectroscopy and single-crystal X-ray analyses indicated that the use of the lacunary heteropolyanion [P2W15O56]12- as an intermediate ensured successful incorporation of the counterions into the mixed-addenda POMs without causing deterioration of the POM frameworks. The hole-transporting layer performance of POM-NH4, which was characterized by a high work function and good conductivity and could be prepared using a low-cost method surpassed those of its protonated counterpart POM-4 and many classic HTL materials. An organic solar cell (OSC) modified with POM-NH4 delivered a power conversion efficiency of 18.0%, which was the highest photovoltaic efficiency achieved by POM-based OSCs to date. Moreover, an HTL material based on POM-NH4 reduced the turn-on voltage of an organic light-emitting diode from 4.2 to 3.2 V. The results of this study suggest that POMs are promising alternatives to the classic HTL materials owing to their excellent hole-collection ability, low costs, neutral nature, and high-chemical stability.
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Affiliation(s)
- Luxin Feng
- State Key Laboratory of Chemical Resource Engineering, College of Materials Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, China
| | - Zhe Li
- State Key Laboratory of Chemical Resource Engineering, College of Materials Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, China
| | - Yuchao Liu
- Key Laboratory of Rubber-Plastics, Ministry of Education, Qingdao University of Science & Technology, Qingdao 266042, P.R. China
| | - Lei Hua
- State Key Laboratory of Chemical Resource Engineering, College of Materials Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, China
| | - Zhengrong Wei
- School of physics, Hubei University, Wuhan 430072, P. R. China
| | - Yuan Cheng
- School of physics, Hubei University, Wuhan 430072, P. R. China
| | - Zhiguo Zhang
- State Key Laboratory of Chemical Resource Engineering, College of Materials Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, China
| | - Bowei Xu
- State Key Laboratory of Chemical Resource Engineering, College of Materials Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, China
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Wang H, Liu S, Yang Y, Li H, Wei Z, Cheng Y, Hou J, Xu B. Reducing the Depletion Region Width at the Anode Interface via a Highly Doped Conjugated Polyelectrolyte Composite for Efficient Organic Solar Cells. ACS Appl Mater Interfaces 2024; 16:3744-3754. [PMID: 38224058 DOI: 10.1021/acsami.3c15126] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/16/2024]
Abstract
In the realm of organic solar cells (OSCs), the width of the depletion region at the anode interface is a critical factor that adversely impacts the open-circuit voltage (Voc) and the power conversion efficiency (PCE). To address this challenge, a novel approach involving a conjugated polyelectrolyte (CPE)-based composite, PCP-2F-Li:POM, has been developed. This composite serves as a solution-processed hole transport layer (HTL), effectively minimizing the depletion region width in high-performance OSCs. The innovative aspect of PCP-2F-Li:POM lies in its "mutual doping" mechanism. Polyoxometalate (POM) is utilized as a dopant, facilitating the formation of p-doped CPE and n-doped POM within the composite. This results in a substantial increase in doping density, nearly 2 orders of magnitude higher than that observed in unmodified CPE. Consequently, the width of depletion region is markedly reduced, shrinking from 76.4 to 6.0 nm. This reduction plays a pivotal role in enhancing hole transport via the tunneling effect. The practical impact of this development is notable. It leads to an increase in Voc from 0.84 to 0.86 V, thereby contributing significantly to an impressive PCE of 18.04% in OSCs. Moreover, the compatibility of PCP-2F-Li:POM with large-area processing techniques underscores its potential as a viable HTL material for future practical applications. Additionally, its contribution to the enhanced long-term stability of OSCs further bolsters its suitability for practical applications.
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Affiliation(s)
- He Wang
- State Key Laboratory of Chemical Resource Engineering, College of Materials Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, China
| | - Shuyan Liu
- State Key Laboratory of Chemical Resource Engineering, College of Materials Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, China
| | - Yi Yang
- State Key Laboratory of Polymer Physics and Chemistry, Beijing National Laboratory for Molecular Sciences Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China
- University of Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Hao Li
- State Key Laboratory of Polymer Physics and Chemistry, Beijing National Laboratory for Molecular Sciences Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China
| | - Zhengrong Wei
- School of Physics, Hubei University, Wuhan 430072, P. R. China
| | - Yuan Cheng
- School of Physics, Hubei University, Wuhan 430072, P. R. China
| | - Jianhui Hou
- State Key Laboratory of Polymer Physics and Chemistry, Beijing National Laboratory for Molecular Sciences Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China
- University of Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Bowei Xu
- State Key Laboratory of Chemical Resource Engineering, College of Materials Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, China
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Xiang Y, Xu B, Li Y. Solution-Processed Semiconductor Materials as Cathode Interlayers for Organic Solar Cells. Adv Sci (Weinh) 2023; 10:e2304673. [PMID: 37882326 DOI: 10.1002/advs.202304673] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2023] [Revised: 08/20/2023] [Indexed: 10/27/2023]
Abstract
Cathode interlayers (CILs) play a crucial role in improving the photovoltaic efficiency and stability of OSCs. CILs generally consists of two kinds of materials, interfacial dipole-based CILs and SPS-based CILs. With good charge transporting ability, excellent compatibility with large-area processing methods, and highly tunable optoelectronic properties, the SPS-based CILs exhibit remarkable superiorities to their interfacial dipole-based counterparts in practical use, making them promising candidate in developing efficient CILs for OSCs. This mini-review highlights the great potential of SPS-based CILs in OSC applications and elucidates the working mechanism and material design strategy of SPS materials. Afterward, the SPS-based CIL materials are summarized and discussed in four sections, including organic small molecules, conjugated polymers, nonconjugated polymers, and TMOs. The structure-property-performance relationship of SPS-based CIL materials is revealed, which may provide readers new insight into the molecular design of SPS-based CILs. The mechanisms to endow SPS-based CILs with thickness insensitivity, resistance to environmental erosion, and photo-electric conversion ability are also elucidated. Finally, after a brief summary, the remaining issues and the prospects of SPS-based CILs are suggested.
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Affiliation(s)
- Yanhe Xiang
- State Key Laboratory of Chemical Resource Engineering, College of Materials Science and Engineering, Beijing University of Chemical Technology, Beijing, 100029, P. R. China
| | - Bowei Xu
- State Key Laboratory of Chemical Resource Engineering, College of Materials Science and Engineering, Beijing University of Chemical Technology, Beijing, 100029, P. R. China
| | - Ying Li
- School of Materials Science and Engineering, Chongqing University of Arts and Sciences, Chongqing, 402160, P. R. China
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Wu J, Chen J, Wang H. Phase Transition Kinetics of MAPbI 3 for Tetragonal-to-Orthorhombic Evolution. JACS Au 2023; 3:1205-1212. [PMID: 37124306 PMCID: PMC10131189 DOI: 10.1021/jacsau.3c00060] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/05/2023] [Revised: 03/07/2023] [Accepted: 03/14/2023] [Indexed: 05/03/2023]
Abstract
Despite the commonly observed phase-instability-induced photovoltaic degradation of MAPbI3, the phase transition kinetics at the atomic level remains elusive. Herein, by developing a stepwise NEB method, we clarify a nonsynergistic minimum-energy pathway for the tetragonal-to-orthorhombic phase transition. It is kinetically driven by the tilting of PbI6 4- that induces a spontaneous small rotation of adjoining MA+ and ends with stepwise ∼110° reorientations of two nonadjacent MA+ enabled by the cavity expansion. Compared to the common concerted mechanism, this process gives a low barrier of 0.08 eV/unit, demonstrating the easiness of the transition at extremely low temperatures and the importance of rotational entropies in regulating transition at elevated temperatures. With an explicit phase transition mechanism, we explore the structure-induced property response and reveal that introducing even low content of large-sized organic cations could help maintain the quasi-stable low-temperature performance of MAPbI3 solar cells.
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Woo JC, Um DS. The Reflectance Characteristics of an Inverse Moth-Eye Structure in a Silicon Substrate Depending on SF 6/O 2 Plasma Etching Conditions. Micromachines (Basel) 2022; 13:1556. [PMID: 36295909 PMCID: PMC9607972 DOI: 10.3390/mi13101556] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/08/2022] [Revised: 09/18/2022] [Accepted: 09/19/2022] [Indexed: 06/16/2023]
Abstract
The global RE100 campaign is attracting attention worldwide due to climate change caused by global warming, increasingly highlighting the efficiency of renewable energy. Texturing of photovoltaic devices increases the devices' efficiency by reducing light reflectance at their surfaces. This study introduces the change in light reflectance following the process conditions of plasma etching as a texturing process to increase the efficiency of photovoltaic cells. Isotropic etching was induced through plasma using SF6 gas, and the etch profile was modulated by adding O2 gas to reduce light reflectance. A high etch rate produces high surface roughness, which results in low surface reflectance properties. The inverse moth-eye structure was implemented using a square PR pattern arranged diagonally and showed the minimum reflectance in visible light at a tip spacing of 1 μm. This study can be applied to the development of higher-efficiency optical devices.
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Affiliation(s)
- Jong-Chang Woo
- Department of Semiconductor Process Equipment, Semiconductor Convergence Campus of Korea Polytechnic, Anseong-si 17550, Gyeonggi-do, Korea
| | - Doo-Seung Um
- Department of Electrical Engineering, Sejong University, Seoul 05006, Korea
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Cai P, Huang X, Zhan T, Chen G, Qiu R, Zhang L, Xue X, Wang Z, Chen J. Cross-Linkable and Alcohol-Soluble Pyridine-Incorporated Polyfluorene Derivative as a Cathode Interface Layer for High-Efficiency and Stable Organic Solar Cells. ACS Appl Mater Interfaces 2021; 13:12296-12304. [PMID: 33682400 DOI: 10.1021/acsami.1c00350] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Device performance and commercialization of organic solar cells (OSCs) are strongly influenced by the characteristics of the interface layers. Cross-linked polymer interface layers with solvent-resistant properties are very compatible with large-area solution-processing methods of OSCs and may be beneficial to the environmental stability of OSCs due to the viscoelastic and cross-linked characteristics of the cross-linked polymer. In this work, a novel cross-linkable and alcohol-soluble pyridine-incorporated polyfluorene derivative, denoted as PFOPy, is synthesized and used as a cathode interface layer (CIL) in OSCs. For PFOPy, the pendant epoxy group can be effectively cross linked through cationic polymerization under thermal treatment and the pendant pyridine group can offer good alcohol solubility. Optical absorption tests of PFOPy films before/after washing by chloroform demonstrate the excellent solvent-resistance property for the cross-linked PFOPy film. Compared with the typical ZnO CIL, the cross-linked PFOPy CIL can also substantially reduce ITO's work function and form a better interface contact with the active layer. Utilizing an inverted device structure and a typical active layer of PM6:Y6, ZnO-based OSCs display an optimal power conversion efficiency (PCE) of 15.83% while PFOPy-based OSCs exhibit superior photovoltaic performance with an optimal PCE of 16.20%. Moreover, ZnO-based and PFOPy-based OSCs separately maintain 89% and 90% of the corresponding initial PCE after 12 h of illumination, indicating similarly excellent photostability. More importantly, after 26 complete thermal cycles, ZnO-based OSCs only maintain 81% of the initial PCE while PFOPy-based OSCs retain 92% of the initial PCE and exhibit obviously better thermal cycling stability, indicating that the cross-linked PFOPy CIL should offer stronger interface robustness against thermal cycling stress due to the viscoelastic and cross-linked characteristics of PFOPy. The impressive results indicate that the cross-linked PFOPy CIL would be a very promising CIL in OSCs.
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Affiliation(s)
- Ping Cai
- School of Materials Science and Engineering & Guangxi Key Laboratory of Information Materials, Guilin University of Electronic Technology, Guilin 541004, P. R. China
| | - Xiaofang Huang
- School of Materials Science and Engineering & Guangxi Key Laboratory of Information Materials, Guilin University of Electronic Technology, Guilin 541004, P. R. China
| | - Tao Zhan
- School of Materials Science and Engineering & Guangxi Key Laboratory of Information Materials, Guilin University of Electronic Technology, Guilin 541004, P. R. China
| | - Guiting Chen
- School of Chemistry and Environment, Jiaying University, Meizhou 514015, P. R. China
| | - Rihang Qiu
- Institute of Polymer Optoelectronic Materials & Devices, State Key Laboratory of Luminescent Materials & Devices, South China University of Technology, Guangzhou 510640, P. R. China
| | - Lianjie Zhang
- Institute of Polymer Optoelectronic Materials & Devices, State Key Laboratory of Luminescent Materials & Devices, South China University of Technology, Guangzhou 510640, P. R. China
| | - Xiaogang Xue
- School of Materials Science and Engineering & Guangxi Key Laboratory of Information Materials, Guilin University of Electronic Technology, Guilin 541004, P. R. China
| | - Zhongmin Wang
- School of Materials Science and Engineering & Guangxi Key Laboratory of Information Materials, Guilin University of Electronic Technology, Guilin 541004, P. R. China
| | - Junwu Chen
- Institute of Polymer Optoelectronic Materials & Devices, State Key Laboratory of Luminescent Materials & Devices, South China University of Technology, Guangzhou 510640, P. R. China
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Chang IY, Kim D, Hyeon-Deuk K. Control of Multiple Exciton Generation and Electron-Phonon Coupling by Interior Nanospace in Hyperstructured Quantum Dot Superlattice. ACS Appl Mater Interfaces 2017; 9:32080-32088. [PMID: 28838230 DOI: 10.1021/acsami.7b08137] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The possibility of precisely manipulating interior nanospace, which can be adjusted by ligand-attaching down to the subnanometer regime, in a hyperstructured quantum dot (QD) superlattice (QDSL) induces a new kind of collective resonant coupling among QDs and opens up new opportunities for developing advanced optoelectric and photovoltaic devices. Here, we report the first real-time dynamics simulations of the multiple exciton generation (MEG) in one-, two-, and three-dimensional (1D, 2D, and 3D) hyperstructured H-passivated Si QDSLs, accounting for thermally fluctuating band energies and phonon dynamics obtained by finite-temperature ab initio molecular dynamics simulations. We computationally demonstrated that the MEG was significantly accelerated, especially in the 3D QDSL compared to the 1D and 2D QDSLs. The MEG acceleration in the 3D QDSL was almost 1.9 times the isolated QD case. The dimension-dependent MEG acceleration was attributed not only to the static density of states but also to the dynamical electron-phonon couplings depending on the dimensionality of the hyperstructured QDSL, which is effectively controlled by the interior nanospace. Such dimension-dependent modifications originated from the short-range quantum resonance among component QDs and were intrinsic to the hyperstructured QDSL. We propose that photoexcited dynamics including the MEG process can be effectively controlled by only manipulating the interior nanospace of the hyperstructured QDSL without changing component QD size, shape, compositions, ligand, etc.
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Affiliation(s)
- I-Ya Chang
- Department of Chemistry, Kyoto University , Kyoto 606-8502, Japan
- PRESTO, Japan Science and Technology Agency , 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan
| | - DaeGwi Kim
- Department of Applied Physics, Osaka City University , Osaka 558-8585, Japan
| | - Kim Hyeon-Deuk
- Department of Chemistry, Kyoto University , Kyoto 606-8502, Japan
- PRESTO, Japan Science and Technology Agency , 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan
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Zhang MJ, Wang N, Pang SP, Lv Q, Huang CS, Zhou ZM, Ji FX. Carrier Transport Improvement of CH 3NH 3PbI 3 Film by Methylamine Gas Treatment. ACS Appl Mater Interfaces 2016; 8:31413-31418. [PMID: 27797470 DOI: 10.1021/acsami.6b10418] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Recently, perovskite solar cells with high photovoltaic performance based on methylammonium lead halide have attracted great interest due to the superior physical properties of the perovskite optical absorption layer. Here, we investigate the interface carrier transport properties of CH3NH3PbI3 film by applying the reported treatment with methylamine gas, to reveal the possible mechanism of high performance perovskite-sensitized solar cell results. It is found that the crystal structure and surface morphology are effectively improved by the room-temperature repair of methylamine atmosphere. The preferred 110 orientation results in a slightly larger band gap, which may contribute to the better energy level matching and carrier transport. Further investigations on relaxation time and electron mobility confirm the significantly enhanced carrier diffusion length, revealing the important role of optimized crystallization on charge transport properties, which may be helpful to seek high-powered perovskite solar cells by optimizing the perovskite synthetic process.
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Affiliation(s)
- Ming-Jia Zhang
- Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences , Qingdao 266101, P.R. China
| | - Ning Wang
- Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences , Qingdao 266101, P.R. China
| | - Shu-Ping Pang
- Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences , Qingdao 266101, P.R. China
| | - Qing Lv
- Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences , Qingdao 266101, P.R. China
| | - Chang-Shui Huang
- Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences , Qingdao 266101, P.R. China
| | - Zhong-Min Zhou
- Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences , Qingdao 266101, P.R. China
| | - Fu-Xiang Ji
- Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences , Qingdao 266101, P.R. China
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Pei K, Wu Y, Li H, Geng Z, Tian H, Zhu WH. Cosensitization of D-A-π-A quinoxaline organic dye: efficiently filling the absorption valley with high photovoltaic efficiency. ACS Appl Mater Interfaces 2015; 7:5296-5304. [PMID: 25710618 DOI: 10.1021/am508623e] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
In the efficient cosensitization, the pure organic sensitizers with high molecular extinction coefficients and long wavelength response are highly preferable since the dye loading amount for each dye in cosensitization is decreased with respect to single dye sensitization. A D-A-π-A featured quinoxaline organic sensitizer IQ21 is specifically designed. The high conjugation building block of 4H-cyclopenta[2,1-b:3,4-b']dithiophene (CPDT) is introduced as the π bridge, instead of the traditional thiophene unit, especially in realizing high molecular extinction coefficients (up to 66 600 M(-1) cm(-1)) and extending the light response wavelength. With respect to the reference dye IQ4, the slightly lower efficiency of IQ21 (9.03%) arises from the decrease of VOC, which offsets the gain in JSC. While cosensitized with a smaller D-π-A dye S2, the efficiency in IQ21 is further improved to 10.41% (JSC = 19.8 mA cm(-2), VOC = 731 mV, FF = 0.72). The large improvement in efficiency is attributed to the well-matched molecular structures and loading amounts of both dyes in the cosensitization system. We also demonstrated that coabsorbent dye S2 can distinctly compensate the inherent drawbacks of IQ21, not only enhancing the response intensity of IPCE, making up the absorption defects around low wavelength region of IPCE, but also repressing the charge recombination rate to some extent.
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Affiliation(s)
- Kai Pei
- Shanghai Key Laboratory of Functional Materials Chemistry, Key Laboratory for Advanced Materials and Institute of Fine Chemicals, Collaborative Innovation Center for Coal Based Energy (i-CCE), East China University of Science and Technology , Shanghai 200237, P. R. China
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