Wang Sisi, Wei Qi, Wang Kaiyang, Zhang Zhipeng, Zhao Dandan, Liang Chao, Liu Tanghao, Guo Jia, Su Chenliang, Li Ying, Xing Guichuan
SZU-NUS Collaborative Center and International Collaborative Laboratory of 2D Materials for Optoelectronic Science & Technology of the Ministry of Education, Engineering Technology Research Center for 2D Materials Information Functional Devices and Systems of Guangdong Province, Institute of Microscale Optoeletronics, Shenzhen University, Shenzhen, 518060, China.
Joint Key Laboratory of the Ministry of Education, Institute of Applied Physics and Materials Engineering, University of Macau, Avenida da Universidade, Taipa, Macau, 999078, China.
Small. 2020 May;16(18):e1907513. doi: 10.1002/smll.201907513. Epub 2020 Apr 19.
Doped 2,2',7,7'-tetrakis(N,N-di-p-methoxyphenylamine)-9,9'-spirobifluorene (spiro-MeOTAD), which acts as a hole-transporting layer (HTL), endows perovskite solar cells (PSCs) with excellent performance. However, the intrinsically hygroscopic nature of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) dopants also aggravates the moisture instability of PSCs. In this work, the origins of the moisture instability of spiro-MeOTAD HTLs are explored and strategies to enhance moisture resistance are proposed. After 780 h of aging in air, 52% of the initial power conversion efficiency (PCE) can be sustained by prolonging the mixing time of the precursor solution of spiro-MeOTAD to reduce accumulated LiTFSI. In contrast, only 7% of the initial PCE remains if the precursor solution is mixed briefly. By thermally annealing an HTL to evaporate residual tBP in spiro-MeOTAD, pinholes are completely eliminated and 65% of the initial PCE remains after the same aging time. In this study, the significance of the initial morphology of spiro-MeOTAD HTLs on device stability is analyzed and strategies based on physical morphology for controlling PSC moisture instability induced by HTL dopants are developed.
掺杂的2,2',7,7'-四（N,N-二对甲氧基苯胺）-9,9'-螺二芴（螺-MeOTAD）作为空穴传输层（HTL），赋予钙钛矿太阳能电池（PSC）优异的性能。然而，双（三氟甲磺酰）亚胺锂（LiTFSI）掺杂剂固有的吸湿性也加剧了PSC的湿度不稳定性。在这项工作中，探索了螺-MeOTAD HTL湿度不稳定性的根源，并提出了提高防潮性的策略。在空气中老化780小时后，通过延长螺-MeOTAD前驱体溶液的混合时间以减少LiTFSI的积累，可以保持52%的初始功率转换效率（PCE）。相比之下，如果前驱体溶液混合时间较短，初始PCE仅保留7%。通过对HTL进行热退火以蒸发螺-MeOTAD中残留的叔丁基吡啶（tBP），针孔被完全消除，在相同老化时间后仍保留65%的初始PCE。在本研究中，分析了螺-MeOTAD HTL的初始形态对器件稳定性的重要性，并开发了基于物理形态的策略来控制由HTL掺杂剂引起的PSC湿度不稳定性。
