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Iodonium Initiators: Paving the Air-free Oxidation of Spiro-OMeTAD for Efficient and Stable Perovskite Solar Cells |
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| Authors: | Heyi Yang Tingting Xu Weijie Chen Yeyong Wu Xianming Guo Yunxiu Shen Chengqiang Ding Xining Chen Haiyang Chen Junyuan Ding Xiaoxiao Wu Prof Guixiang Zeng Prof Zhengbiao Zhang Prof Yaowen Li Prof Yongfang Li |
| Institution: | 1. Laboratory of Advanced Optoelectronic Materials, Suzhou Key Laboratory of Novel Semiconductor-optoelectronics Materials and Devices, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, 215123 China;2. School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210008 China;3. State and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials, Jiangsu Key Laboratory of Advanced Functional Polymer Design and Application, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, 215123 China;4. Kuang Yaming Honors School, Nanjing University, Nanjing, 210008 China;5. Laboratory of Advanced Optoelectronic Materials, Suzhou Key Laboratory of Novel Semiconductor-optoelectronics Materials and Devices, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, 215123 China
Jiangsu Key Laboratory of Advanced Negative Carbon Technologies, Soochow University, Suzhou, 215123 China Beijing National Laboratory for Molecular Sciences;6. CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190 China |
| Abstract: | To date, perovskite solar cells (pero-SCs) with doped 2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenylamine)-9,9′-spirobifluorene (Spiro-OMeTAD) hole transporting layers (HTLs) have shown the highest recorded power conversion efficiencies (PCEs). However, their commercialization is still impeded by poor device stability owing to the hygroscopic lithium bis(trifluoromethanesulfonyl)imide and volatile 4-tert-butylpyridine dopants as well as time-consuming oxidation in air. In this study, we explored a series of single-component iodonium initiators with strong oxidability and different electron delocalization properties to precisely manipulate the oxidation states of Spiro-OMeTAD without air assistance, and the oxidation mechanism was clearly understood. Iodine (III) in the diphenyliodonium cation (IP+) can accept a single electron from Spiro-OMeTAD and forms Spiro-OMeTAD⋅+ owing to its strong oxidability. Moreover, because of the coordination of the strongly delocalized TFSI− with Spiro-OMeTAD⋅+ in a stable radical complex, the resulting hole mobility was 30 times higher than that of pristine Spiro-OMeTAD. In addition, the IP-TFSI initiator facilitated the growth of a homogeneous and pinhole-free Spiro-OMeTAD film. The pero-SCs based on this oxidizing HTL showed excellent efficiencies of 25.16 % (certified: 24.85 % for 0.062-cm2) and 20.71 % for a 15.03-cm2 module as well as remarkable overall stability. |
| Keywords: | Doping Perovskite Solar Cells Spiro-OMeTAD Stability |