Pre-Buried Additive for Cross-Layer Modification in Flexible Perovskite Solar Cells with Efficiency Exceeding 22.

Zheng, Zhonghao; Li, Faming; Gong, Jue; Ma, Yinyi; Gu, Jinwen; Liu, Xiaochun; Chen, Shuhan; Liu, Mingzhen · Adv Mater · 2022

basic_science · Level V

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Abstract

Halide perovskites have shown superior potentials in flexible photovoltaics due to their soft and high power-to-weight nature. However, interfacial residual stress and lattice mismatch due to the large deformation of flexible substrates have greatly limited the performance of flexible perovskite solar cells (F-PSCs). Here, ammonium formate (HCOONH<sub>4</sub> ) is used as a pre-buried additive in electron transport layer (ETL) to realize a bottom-up infiltration process for an in situ, integral modification of ETL, perovskite layer, and their interface. The HCOONH<sub>4</sub> treatment leads to an enhanced electron extraction in ETL, relaxed residual strain and micro-strain in perovskite film, along with reduced defect densities within these layers. As a result, a top power conversion efficiency of 22.37% and a certified 21.9% on F-PSCs are achieved, representing the highest performance reported so far. This work links the critical connection between multilayer mechanics/defect profiles of ETL-perovskite structure and device performance, thus providing meaningful scientific direction to further narrowing the efficiency gap between F-PSCs and rigid-substrate counterparts.