Material Properties Modulation in Inorganic Perovskite Films via Solution-Free Solid-State Reactions

A simple solvent-free, versatile, and flexible route for material properties modulation in halide perovskite thin films has been developed using CsPbBr3 thin films. The method further enables composition and morphology control using a solid-state ion-exchange reaction in the presence of PbX2 (X= Cl, Br, I) vapor in a close-spaced sublimation deposition system. The morphology, structure, and optoelectronic properties of the resulting CsPb(Br1–xXx)3 (X = Cl, Br, I) films, as well as the performance of PN junction diodes are systematically investigated and discussed. The CsPb(Br1–xXx)3 films maintained an orthorhombic structure with increased mobility and remarkable grain growth with grains as large as 25 μm in films as thick as 8 μm. The CsPb(Br1–xXx)3 films enabled diodes with a very low leakage current (1 × 10–8 A/mm2), likely due to the large crystalline grains. The diodes were used as radiation detectors, with superior alpha particle sensing from a 210Po source. This simple, scalable, solution-free, and cost-effective perovskite annealing process can be applied in other perovskite systems to also tune their band gap in the range of 1.7–2.9 eV and tailor their transport electronic properties to further expand the application of these exceptional materials.