Retarding solid-state reactions enable efficient and stable all-inorganic perovskite solar cells and modules
Cheng Liu, Xiuhong Sun, Yi Yang, Olga A. Syzgantseva, Maria A. Syzgantseva, Bin Ding, Naoyuki Shibayama, Hiroyuki Kanda, Farzaneh Fadaei‐Tirani, Rosario Scopelliti, Shunlin Zhang, Keith G. Brooks, Songyuan Dai, Guanglei Cui, Michael D. Irwin, Zhipeng Shao, Yong Ding, Zhaofu Fei, Paul J. Dyson, Mohammad Khaja Nazeeruddin
Abstract
All-inorganic CsPbI 3 perovskite solar cells (PSCs) with efficiencies exceeding 20% are ideal candidates for application in large-scale tandem solar cells. However, there are still two major obstacles hindering their scale-up: (i) the inhomogeneous solid-state synthesis process and (ii) the inferior stability of the photoactive CsPbI 3 black phase. Here, we have used a thermally stable ionic liquid, bis (triphenylphosphine)iminium bis (trifluoromethylsulfonyl)imide ([PPN][TFSI]), to retard the high-temperature solid-state reaction between Cs 4 PbI 6 and DMAPbI 3 [dimethylammonium (DMA)], which enables the preparation of high-quality and large-area CsPbI 3 films in the air. Because of the strong Pb-O contacts, [PPN][TFSI] increases the formation energy of superficial vacancies and prevents the undesired phase degradation of CsPbI 3 . The resulting PSCs attained a power conversion efficiency (PCE) of 20.64% (certified 19.69%) with long-term operational stability over 1000 hours. A record efficiency of 16.89% for an all-inorganic perovskite solar module was achieved, with an active area of 28.17 cm 2 .