Solid-phase hetero epitaxial growth of α-phase formamidinium perovskite.

Lee, Jin-Wook; Tan, Shaun; Han, Tae-Hee; Wang, Rui; Zhang, Lizhi; Park, Changwon; Yoon, Mina; Choi, Chungseok et al. · Nat Commun · 2020

basic_science · Level V

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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<sub>3</sub>) perovskite films. The layered perovskite templates the solid-state phase conversion of FAPbI<sub>3</sub> 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<sub>3</sub> showed efficiencies and stabilities superior to those of devices fabricated without NHE.