Solid-phase hetero epitaxial growth of α-phase formamidinium perovskite
Jin‐Wook Lee, Shaun Tan, Tae Hee Han, Rui Wang, Lizhi Zhang, Changwon Park, Mina Yoon, Chungseok Choi, Mingjie Xu, Michael E. Liao, Sung‐Joon Lee, Selbi Nuryyeva, Chenhui Zhu, Kenny Huynh, Mark S. Goorsky, Yu Huang, Xiaoqing Pan, Yang Yang
Abstract
Abstract Conventional epitaxy of semiconductor films requires a compatible single crystalline substrate and precisely controlled growth conditions, which limit the price competitiveness and versatility of the process. We demonstrate substrate-tolerant nano-heteroepitaxy (NHE) of high-quality formamidinium-lead-tri-iodide (FAPbI 3 ) perovskite films. The layered perovskite templates the solid-state phase conversion of FAPbI 3 from its hexagonal non-perovskite phase to the cubic perovskite polymorph, where the growth kinetics are controlled by a synergistic effect between strain and entropy. The slow heteroepitaxial crystal growth enlarged the perovskite crystals by 10-fold with a reduced defect density and strong preferred orientation. This NHE is readily applicable to various substrates used for devices. The proof-of-concept solar cell and light-emitting diode devices based on the NHE-FAPbI 3 showed efficiencies and stabilities superior to those of devices fabricated without NHE.