Facet Orientation-Dependent Strain Relaxation Stabilizes FAPbI<sub>3</sub> Perovskite Solar Cells
Tinghuan Yang, Yang Yang, Tianqi Niu, Erxin Zhao, Nan Wu, Shuang Wang, Xin Chen, Shumei Wang, Yajie Wang, Yin Wu, Zheng Zhang, Cheng Ma, Yongshuai Gong, Dongxue Liu, Kui Zhao
Abstract
The exclusive orientation of a singular perovskite facet during crystallization can lead to significant strain accumulation in solution-processed films, compromising the performance of perovskite solar cells (PSCs). To address this issue, we propose a facet-complementarity strategy through crystallization modulation utilizing a formamidine-based additive 1-(2-fluorobenzyl)-1 H -pyrazolo[3,4- b ]pyridine-3-carboximidamide hydrochloride (FPPC) to control strain accumulation. The FPPC ligand shows strong adsorption on the (111) facet of perovskite via chemical interactions with octahedra lattice, promoting the formation of a more stable (111) facet against the preferred (100) orientation and achieving facet complementarity in the FAPbI 3 film. Additionally, the increased dissociation barrier of the ligand-PbI 2 bonding extends the crystallization growth window, allowing for a better lattice rearrangement and a balanced crystallization rate from bulk to surface. As a result, the facet-complementary devices achieve champion efficiencies of 25.63 and 24.26% on 0.09 and 1.0 cm 2 scales, respectively, with greatly enhanced device longevity.