Chalcohalide semiconductors have recently emerged as attractive materials for photovoltaic and optoelectronic applications. However, many of these compositions are extremely difficult to synthesize using solution-phase techniques which can often enhance synthetic control over particle size and phase purity. Therefore, there it is highly desirable to develop colloidal synthetic methods for nanocrystalline multinary chalcohalides. We report the solution-phase synthesis and characterization of two such quaternary chalcohalides, Pb2SbS2I3 and Pb2BiS2I3, using a thiocyanate-based approach. Controlling the organic ligand concentration allows us to isolate rod-like morphologies with varying diameters and aspect ratios. Fluorescence microscopy reveals remarkable photoluminescence in Pb2SbS2I3 on the single particle level in addition to its bulk emission. Cyclic voltammetry and absorbance measurements provide a comprehensive analysis of the band gap and band edge energies of the two quaternaries compared to their ternary analogs. Lastly, we use electronic structure calculations to evaluate the effect of crystallographic disorder on the band gap of the two known Pb2SbS2I3 polymorphs. The synthetic methods developed here will be advantageous for investigating more complex mixed-metal chalcohalides.

Synthesis and characterization of quaternary lead chalcohalide nanocrystals

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