Cesium lead halide perovskite nanocrystals (NCs) are the most promising materials for photovoltaic and optoelectronic applications in recent years. However, lack of long-term stability and consequent deterioration of optical properties with time have been major challenges for commercialization of the perovskite-based devices. In this context, we report that even room-temperature treatment of blue-emitting CsPbCl1.5Br1.5 and CsPbClBr2 NCs, green-emitting CsPbBr3 NCs, and yellow-emitting CsPbBr1.5I1.5 NCs with sodium thiosulfate (Na2S2O3 center dot 5H(2)O) can not only lead to huge enhancement of the photoluminescence quantum yield (PLQY, to similar to 100% for the blue/green-emitting NCs and similar to 90% for the yellow-emitting NCs) but also add superior stability to these NCs under different environmental stresses. While the time-resolved PL and ultrafast transient absorption studies show suppression of the nonradiative recombination channels, other measurements reveal that the improved optical characteristics and stability of these substances are by the formation of Pb-S bonds between undercoordinated surface Pb and thiosulfate. The outstanding PLQY and much improved long-term stability of the treated NCs make them attractive components for perovskite-based optoelectronic applications.
