Bright Self-Trapped Exciton Emission in Alkali Iodide Nanocrystals via Sn(II)-Doping

Abstract

Lead-free alkali halides have gained increasingly attentions due to their desire optoelectronic properties across a variety of light-emitting applications. However, state-of-the art alkali halide emitters commonly are bulky crystals functionalized with highly toxic elemental doping, hindering their integration into emerging flexible, wearable and large-area optoelectronic devices. Here, we managed to develop environmental-friendly and solution-processable alkali halide nanocrystals (RbI and RbxCs1-xI) that exhibit intense self-trapped emission facilitated by Sn2+ ionic doping. We find that the presence of Sn2+-interstitial leads to tilting of cubic structures of RbI and thus trigger the self-trapped emission. The resultant Sn2+-doped nanocrystals display an impressive maximum photoluminescence quantum yield of 91.9% and exhibit remarkable stability in ambient. These findings pave the way for a new class of bright, solution-processable alkali halides, with diverse applications such as energy down conversion and flexible scintillation technologies.