Single‐Source, Solvent‐Free, Room Temperature Deposition of Black γ‐CsSnI<sub>3</sub> Films
Vivien M. Kiyek, Yorick A. Birkhölzer, Yury Smirnov, Martin Ledinsky, Zdenek Remes, Jamo Momand, Bart J. Kooi, Gertjan Koster, Guus Rijnders, Monica Morales‐Masis
Abstract
Abstract The presence of a nonoptically active polymorph (yellow‐phase) competing with the optically active polymorph (black γ‐phase) at room temperature in cesium tin iodide (CsSnI 3 ) and the susceptibility of Sn to oxidation represent two of the biggest obstacles for the exploitation of CsSnI 3 in optoelectronic devices. Here room‐temperature single‐source in vacuum deposition of smooth black γ −CsSnI 3 thin films is reported. This is done by fabricating a solid target by completely solvent‐free mixing of CsI and SnI 2 powders and isostatic pressing. By controlled laser ablation of the solid target on an arbitrary substrate at room temperature, the formation of CsSnI 3 thin films with optimal optical properties is demonstrated. The films present a bandgap of 1.32 eV, a sharp absorption edge, and near‐infrared photoluminescence emission. These properties and X‐ray diffraction of the thin films confirm the formation of the orthorhombic (B‐γ ) perovskite phase. The thermal stability of the phase is ensured by applying in situ an Al 2 O 3 capping layer. This work demonstrates the potential of pulsed laser deposition as a volatility‐insensitive single‐source growth technique of halide perovskites and represents a critical step forward in the development and future scalability of inorganic lead‐free halide perovskites.