Composition-tunable structural and optical properties of dual-phase cesium tin bromide perovskite semiconductors

The inorganic lead-based metal halide perovskites are widely studied for optoelectronic applications because of their tunable structural, optical and electrical properties. On the other hand, due to the instability and toxicity of lead-based perovskites, it is difficult to apply them on a large-scale. The lead-free nature and air stability of dual-phase tin (Sn)-based halide perovskites make them as possible candidates to replace lead (Pb)-based perovskites. For the first time, Composition-tunable structural and optical properties of dual-phase CsSnBr₃–CsSn₂Br₅, Cs₂SnBr₄–CsBr, and Cs₄SnBr₆–CsSnBr₃ perovskite semiconductors were synthesized and comprehensively reported here. The perovskites were prepared using a composition (CsBr–SnBr₂), mechano-chemical and water-induced solvent precipitation method. In addition, the structural, optical and thermal properties were investigated. XRD analysis confirms the layered crystal structure of perovskite composites. FESEM studies demonstrate the formation of aggregate crystals of various sizes. The optical absorption spectrum was used to calculate the enhanced optical properties. The bandgap was reduced from 2.61 to 2.27 eV. The PL spectrum confirms that light is emitting in the yellow and green color regions. The prepared perovskite semiconductors have the potential for various optoelectronic applications.