Solution-Grown CsPbBr₃ /Cs₄ PbBr₆ Perovskite Nanocomposites: Toward Temperature-Insensitive Optical Gain

With regards to developing miniaturized coherent light sources, the temperature-insensitivity in gain spectrum and threshold is highly desirable. Quantum dots (QDs) are predicted to possess a temperature-insensitive threshold by virtue of the separated electronic states; however, it is never observed in colloidal QDs due to the poor thermal stability. Besides, for the classical II-VI QDs, the gain profile generally redshifts with increasing temperature, plaguing the device chromaticity. Herein, this paper addresses the above two issues simultaneously by embedding ligands-free CsPbBr₃ nanocrystals in a wider band gap Cs₄ PbBr₆ matrix by solution-phase synthesis. The unique electronic structures of CsPbBr₃ nanocrystals enable temperature-insensitive gain spectrum while the lack of ligands and protection from Cs₄ PbBr₆ matrix ensure the thermal stability and high temperature operation. Specifically, a color drift-free stimulated emission irrespective of temperature change (20-150 °C) upon two-photon pumping is presented and the characteristic temperature is determined to be as high as ≈260 K. The superior gain properties of the CsPbBr₃ /Cs₄ PbBr₆ perovskite nanocomposites are directly validated by a vertical cavity surface emitting laser operating at temperature as high as 100 °C. The results shed light on manipulating optical gain from the advantageous CsPbBr₃ nanocrystals and represent a significant step toward the temperature-insensitive frequency-upconverted lasers.