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.