Highly‐Stable CsPbI<sub>3</sub> Perovskite Solar Cells with an Efficiency of 21.11% via Fluorinated 4‐Amino‐Benzoate Cesium Bifacial Passivation
Dongfang Xu, Jungang Wang, Yuwei Duan, Shaomin Yang, Hong Zou, Lu Yang, Na Zhang, Hui Zhou, Xuruo Lei, Meizi Wu, Shengzhong Liu, Zhike Liu
Abstract
Abstract The poor interface quality between cesium lead triiodide (CsPbI 3 ) perovskite and the electron transport layer limits the stability and efficiency of CsPbI 3 perovskite solar cells (PSCs). Herein, a 4‐amino‐2,3,5,6‐tetrafluorobenzoate cesium (ATFC) is designed as a bifacial defect passivator to tailor the perovskite/TiO 2 interface. The comprehensive experiments demonstrate that ATFC can not only optimize the conductivity, electron mobility, and energy band structure of the TiO 2 layer by passivation of the undercoordinated Ti 4+ , oxygen vacancy ( V O ), and free OH defects but also promote the yield of high‐quality CsPbI 3 film by synergistic passivation of undercoordinated Pb 2+ defects with the CO group and F atom, and limiting I − migration via F···I interaction. Benefiting from the above interactions, the ATFC‐modified CsPbI 3 device yields a champion power conversion efficiency (PCE) of 21.11% and an excellent open‐circuit voltage ( V OC ) of 1.24 V. Meanwhile, the optimized CsPbI 3 PSC maintains 92.74% of its initial efficiency after aging 800 h in air atmosphere, and has almost no efficiency attenuation after tracking at maximum power point for 350 h.