Lead-free cesium antimony halide perovskites: halide alloying, surfaces, interfaces, and clusters

Lead-free Cs3Sb2X9 (X = Cl, Br, I) perovskites have emerged as eco-friendly alternatives to traditional photovoltaic and optoelectronic materials. This research uses DFT for a comprehensive analysis, bridging knowledge gaps about halide alloying, structural changes, and surface properties on these materials. Analysis of enthalpy of formation and miscibility gap temperature pointed to which solid solutions of Cs3Sb2X9-nXn' are more likely to be experimentally obtained. CsX-terminated low-index (1000) and (0001) surfaces present distinct electronic properties, underscoring the importance of surface control during materials preparation in fine-tuning for photovoltaic and photocatalytic applications. The properties of Cs3Sb2X9 nanocrystals were estimated through cluster simulations, shedding light on the role of geometry as a possible contributor to the high photo-luminescence observed in previous experimental reports on Cs3Sb2Br9 nanocrystals. The study on halide perovskite interfaces suggested Cs3Sb2Br9|Cs3Sb2I9 for photovoltaics and Cs3Sb2Br9|Cs3Sb2Cl9 for photoluminescence, based on band alignment and electronic structure. Our findings not only advance the fundamental understanding of lead-free Cs3Sb2X9 perovskites but also provide practical guidance for experimentalists in designing cesium antimony halide perovskites with tailored optical and electronic properties. This contributing supports the development of sustainable energy solutions for optoelectronic devices.