Role of CsMnCl₃ Nanocrystal Structure on Its Luminescence Properties

Cesium manganese chloride (CsMnCl3) nanocrystals (NCs) have recently been recognized as potential lead-free perovskite candidates for red emission. To ascertain how the luminescence properties depend on NC structures formed under different synthesis conditions, we synthesized CsMnCl3 NCs in two polymorphic structures, namely, cubic (c-CsMnCl3) and rhombohedral (r-CsMnCl3), by tuning reaction temperature of a hot injection route. c-CsMnCl3 are found to be nonemissive, whereas r-CsMnCl3 exhibit emission at 670 nm with photoluminescence quantum yield 40%. Density functional theory calculations reveal an indirect band gap c-CsMnCl3─the electronic transitions between valence conduction edges prohibited orbital symmetry spin. Conversely, possess direct gap. Further, transient absorption measurements suggest self-trapped exciton formation NCs, which contributes their characteristics. Our proof-of-concept demonstration photocurrent generated from emitting indicates suitability luminescent solar concentrator applications. The findings this work highlight importance understanding structure-luminescence relationship emerging perovskites providing design criteria red-emitting materials.