Directed Texturing of Metal-Halide Perovskite Films via Vapor Transport Deposition

Metal-halide perovskites are a promising material for solar cell applications, with device power conversion efficiencies exceeding 25%. Thin films of perovskites can be grown via both solution and vapor-based processing techniques. As perovskites move towards commercialization, examination of the impact of different processing techniques on materials properties is critical. Here, we demonstrate the ability to tune the relative orientation of lead iodide precursor platelets in thin films via vapor transport deposition (VTD). VTD is a moderate vacuum thin film processing technique that relies on an inert carrier gas to carry sublimated precursor materials to a cooled substrate. This technique has a broad processing parameter space, allowing us to probe the impact of variations in carrier gas flow rate, substrate temperature, and substrate material on film texture. We further demonstrate that the orientation of the lead iodide precursor strongly impacts the orientation of the final perovskite film; highlighting both a likely growth mechanism for perovskite materials deposited via VTD and the capacity to tune perovskite film crystallinity using VTD. Differences in film texturing for lead iodide as well as perovskite films are found both via 2D X-ray diffraction measurements and electron microscopy images.