Fine‐Tuning of Molecular Packing and Energy Level through Methyl Substitution Enabling Excellent Small Molecule Acceptors for Nonfullerene Polymer Solar Cells with Efficiency up to 12.54% |
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| Authors: | Zhenghui Luo Haijun Bin Tao Liu Zhi‐Guo Zhang Yankang Yang Cheng Zhong Beibei Qiu Guanghao Li Wei Gao Dongjun Xie Kailong Wu Yanming Sun Feng Liu Yongfang Li Chuluo Yang |
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| Affiliation: | 1. Hubei Key Lab on Organic and Polymeric Optoelectronic Materials, Department of Chemistry, Wuhan University, Wuhan, P. R. China;2. Shenzhen Key Laboratory of Polymer Science and Technology, College of Materials Science and Engineering, Shenzhen University, Shenzhen, China;3. CAS Research/Education Center for Excellence in Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing, China;4. Heeger Beijing Research and Development Center, School of Chemistry and Environment, Beihang University, Beijing, P. R. China;5. Department of Physics and Astronomy and Collaborative Innovation Center of IFSA (CICIFSA), Shanghai Jiaotong University, Shanghai, P. R. China |
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| Abstract: | A novel small molecule acceptor MeIC with a methylated end‐capping group is developed. Compared to unmethylated counterparts (ITCPTC), MeIC exhibits a higher lowest unoccupied molecular orbital (LUMO) level value, tighter molecular packing, better crystallites quality, and stronger absorption in the range of 520–740 nm. The MeIC‐based polymer solar cells (PSCs) with J71 as donor, achieve high power conversion efficiency (PCE), up to 12.54% with a short‐circuit current (JSC) of 18.41 mA cm?2, significantly higher than that of the device based on J71:ITCPTC (11.63% with a JSC of 17.52 mA cm?2). The higher JSC of the PSC based on J71:MeIC can be attributed to more balanced μh/μe, higher charge dissociation and charge collection efficiency, better molecular packing, and more proper phase separation features as indicated by grazing incident X‐ray diffraction and resonant soft X‐ray scattering results. It is worth mentioning that the as‐cast PSCs based on MeIC also yield a high PCE of 11.26%, which is among the highest value for the as‐cast nonfullerene PSCs so far. Such a small modification that leads to so significant an improvement of the photovoltaic performance is a quite exciting finding, shining a light on the molecular design of the nonfullerene acceptors. |
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| Keywords: | molecular packing polymer solar cells power conversion efficiencies small molecular acceptors |
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