Single Crystal Seed Induced Epitaxial Growth Stabilizes α-FAPbI<sub>3</sub> in Perovskite Solar Cells.

Cheng, Qian; You, Shuai; Zhang, Weichuan; Xie, Meiling; Yue, Tong; Tian, Chenyang; Zhang, Hong; Wei, Zhixiang et al. · Nano Lett · 2024

basic_science · Level V

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Abstract

FAPbI<sub>3</sub> stands out as an ideal candidate for the photoabsorbing layer of perovskite solar cells (PSCs), showcasing outstanding photovoltaic properties. Nonetheless, stabilizing photoactive α-FAPbI<sub>3</sub> remains a challenge due to the lower formation energy of the competitive photoinactive δ-phase. In this study, we employ tetraethylphosphonium lead tribromide (TEPPbBr<sub>3</sub>) single crystals as templates for the epitaxial growth of PbI<sub>2</sub>. The strategic use of TEPPbBr<sub>3</sub> optimizes the evolution of intermediates and the crystallization kinetics of perovskites, leading to high-quality and phase-stable α-FAPbI<sub>3</sub> films. The TEPPbBr<sub>3</sub>-modified perovskite exhibits optimized carrier dynamics, yielding a champion efficiency of 25.13% with a small voltage loss of 0.34 V. Furthermore, the target device maintains 90% of its initial PCE under maximum power point (MPP) tracking over 1000 h. This work establishes a promising pathway through single crystal seed based epitaxial growth for achieving satisfactory crystallization regulation and phase stabilization of α-FAPbI<sub>3</sub> perovskites toward high-efficiency and stable PSCs.