Silylative Decarboxylation vs Heat-up Synthesis of Chalcohalide Nanocrystals: Pushing the Size and Composition Envelope

Chalcohalide semiconductors are rapidly gaining traction as stable, biocompatible materials for energy conversion applications. While the solid-state synthesis of bulk chalcohalides is relatively well-developed, the colloidal chemistry of these materials is still in its early stages. Colloidal semiconductors are often advantageous in device fabrication due to the cost effectiveness of solution processing. Thus, we aim to increase the utility of chalcohalides in device fabrication by establishing solution phase chemistry of promising compositions. We show that silylative decarboxylation is a versatile and effective method of making colloidal PnChI (Pn = Sb, Bi; Ch = S, Se) and Sn2PnS2I3 (Pn = Sb, Bi) chalcohalide nanocrystals of tunable sizes and compositions. Furthermore, we demonstrate the preparation of mixed-pnictide chalcohalides through silylative decarboxylation and/or cation exchange, the latter being one of the few reported instances in chalcohalides. Additionally, we use the thiocyanate heat up approach in combination with density functional theory to study halide mixing in quaternary tin chalcohalides. By pushing the limits of each synthetic technique, we have designed more soluble chalcohalide nanocrystals with tunable compositions while also gaining a better understanding of the efficacy of each procedure in respect to thin film and subsequent device fabrication. These results may help facilitate the future development and wide-scale application of chalcohalide-based devices for energy conversion.