Morphology-dependent charge recombination through localized states in polymer/polymer blend solar cells |
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| Affiliation: | 1. State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, PR China;2. University of Chinese Academy of Sciences, Beijing 100049, PR China;1. Chemical Engineering and Materials Science, University of California, Davis, CA, 95616, USA;2. Advanced Detector Group, Lawrence Livermore National Laboratory, Livermore, CA, 94550, USA;1. Laboratory of Advanced Optoelectronic Materials, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, China;2. Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China;1. State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, 155 Yangqiao West Road, Fuzhou, Fujian 350002, PR China;2. University of Chinese Academy of Sciences, Beijing 100049, PR China;3. State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an, Shaanxi 710049, PR China;1. Key Laboratory of Luminescence and Optical Information, Ministry of Education, Beijing Jiaotong University, Beijing 100044, PR China;2. State Key Laboratory of Catalysis, Dalian institute of Chemical Physics, Chinese Academy of Sciences, Dalian National Laboratory for Clean Energy, 457 Zhongshan Road, Dalian 116023, PR China;1. School of Material Science and Engineering, Tianjin University, Tianjin 300072, PR China;2. State Key Laboratory of Polymer Physics and Chemistry, Chinese Academy of Sciences, Changchun 130022, PR China;3. Tianjin Key Laboratory of Molecular Optoelectronic Science, Tianjin University, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin 300072, PR China |
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| Abstract: | Polymer solar cells (PSCs) based on the PBDTTT-EFT (polymer donor):N2200 (polymer acceptor) blend have been fabricated with the active layer processed with various solvents including o-dichlorobenzene (o-DCB), chlorobenzene (CB), chloroform (CF), and CF:p-xylene (PX) mixed solvent. A highest power conversion efficiency (PCE) of 5.37% is achieved with the active layer processed with CF:PX mixed solvent. The dependence of short-circuit current density (JSC) on incident light intensity indicates that the charge recombination is to some extent suppressed in the device with the active layer processed with the CF:PX mixed solvent and results in an enhanced JSC. Morphology studies disclosed that the domains are preferential face-on orientation in the active layers processed with o-DCB, CB and CF, while it shows a combined face-on and edge-on orientation in CF:PX-processed film. The long-lived trap-assisted charge recombination originated from the active layer morphological variance has been focused on and investigated. And the nanosecond transient absorption experiment further demonstrated that the PBDTTT-EFT:N2200 film processed with o-DCB shows obvious long-lived trap-assisted charge recombination, while the trap-assisted charge recombination is effectively suppressed in the PBDTTT-EFT:N2200 film processed with CF:PX mixed solvent. This implies that deep localized traps correlated with the PBDTTT-EFT:N2200 morphology are reduced by using the CF:PX mixed solvent to process the active layer. In addition, the domains with a mixed orientation in the active layer may also enhance the three-dimensional charge transport and hence improve the charge-collection efficiency. |
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| Keywords: | Localized states Recombination Orientation Polymer blend solar cells |
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