Room-temperature epitaxy of α-CH₃NH₃PbI₃ halide perovskite by pulsed laser deposition

Epitaxial growth on lattice-(mis)matched substrates has advanced the understanding of semiconductors and enabled high-end technologies such as III-V-based light-emitting diodes. However, for metal halide perovskites, there is a knowledge gap in thin film heteroepitaxial growth, hindering progress towards new applications. Here we demonstrate the epitaxial growth of cubic (α)-CH₃NH₃PbI₃ films on lattice-matched KCl substrates by pulsed laser deposition at room temperature. Epitaxial stabilization of α-CH₃NH₃PbI₃ is confirmed via reciprocal space mapping, X-ray diffraction pole figures, electron backscatter diffraction and photoluminescence. A bandgap of 1.66 eV stable for over 300 days and Urbach energies of 12.3 meV for 15-nm-thick films are demonstrated. The impact of strain on α-phase stabilization is corroborated by first-principles density functional theory calculations, which also predict substantial bandgap tunability. This work demonstrates the potential of pulsed laser deposition for vapour-phase heteroepitaxial growth of metal halide perovskites, inspiring studies to unlock novel functionalities. (Figure presented.)