Vapor deposition of CsPbBr3 thin films by evaporation of CsBr and PbBr2

Thin films of the inorganic halide perovskite, CsPbBr3, find applications in various optoelectronic devices, including solar cells, radiation detectors, light-emitting diodes, photodetectors, and lasers. Physical vapor deposition (PVD) by coevaporation of CsBr and PbBr2 onto a substrate is a scalable solventless approach to forming high purity large-grained polycrystalline films. Herein, we investigate the effects of deposition temperature, between 26 and 162 degrees C, and postdeposition annealing, between 250 and 350 degrees C, on the structure, texturing, and morphology of orthorhombic CsPbBr3 films formed by PVD. All films, regardless of the stable phase at the deposition temperature, transform to orthorhombic upon cooling to room temperature. The films deposited as orthorhombic or tetragonal CsPbBr3 below 130 degrees C were textured in the orthorhombic structure's ⟨202⟩ direction, while cubic CsPbBr3 films deposited above 130 degrees C were textured in the orthorhombic structure's ⟨121⟩ direction. This texturing favors the growth of high cation density planes of the stable phase at the deposition temperature. The orthorhombic ⟨202⟩ texturing also dominates after annealing as long as the films have ⟨202⟩ aligned grains before annealing.