Optimized mixed phases to achieve improved performance of organic solar cells
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Research Letter
Optimized mixed phases to achieve improved performance of organic solar cells Yanlin Yi, State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China; State Key Laboratory of Fine Chemicals, School of Petroleum and Chemical Engineering, Dalian University of Technology, Panjin, Liaoning 124221, China Xu Gao, State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China Jian Yuan, State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an 710049, China Jiangang Liu, State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China Wei Ma, State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an 710049, China Yanchun Han, State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China Address all correspondence to Yanchun Han at [email protected] (Received 18 June 2019; accepted 4 October 2019)
Abstract In the three-phase (pure donor, pure acceptor, and mixed phases) morphologies of organic solar cells, the mixed phases produce an energy cascade that promotes the generation of free carriers. However, how to optimize the content of the mixed phases is a challenging problem. The authors proposed to control different content of mixed phases in DRTB-T and IDIC blends by additive and solvent vapor annealing (SVA). The authors first formed the largest extent amount of mixed phases by the additive cinene (2%) to inhibit the crystallization of DRTB-T and IDIC. And then, different amounts of mixed phases were achieved by further SVA for different times (from 0 to 50 s) to increase the content of pure DRTB-T and IDIC phases. The energetic offsets (ΔE) of pure and mixed phases gradually decrease from 0.529 to 0.477 eV for different content of mixed phases. When ΔE was 0.498 eV, the highest photocurrent density (Jsc) was obtained. The power conversion efficiency was increased from 3.23% (without any treatment) to 8.54%. Therefore, the authors demonstrated that the optimized content of the mixed phases is critical to device performance.
Introduction It is an important aspect to improve the separation efficiency of excitons in the bulk heterojunction active layer of organic solar cells (OSCs).[1–4] During the process of exciton separation, the excitons migrate to the interface of the donor and the acceptor due to the concentration gradient. In organic semiconductor materials, singlet excitons binding energy is about 0.5 eV, while thermal energy at normal temperature is only about 25 meV, so it is impossible to drive exciton separation to generate free carriers.[1,5,6] Therefore, the heterojunction in the active layer film serves to promote efficient separation of excitons. At the interface, due to the different e
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