Pressure-Driven Abnormal Emission Blue-Shift of Lead-Free Halide Double Perovskite Cs₂AgInCl₆ Nanocrystals

Lead-free halide double perovskites (DPs) have been proposed as stable and promising alternatives to lead halide perovskites. Understanding the structural-optical properties of halide DPs is important for their applications. In this study, Cs₂AgInCl₆ DP nanocrystals, with a direct band gap, were synthesized and studied. Because of a strong electron-phonon coupling leading to exciton self-trapping, a broad emission with a large Stokes shift of Cs₂AgInCl₆ DP nanocrystals is observed. We observed an abnormal blue-shifted emission accompanied by a red-shifted direct absorption edge because of the reduced electron-phonon coupling under compression in the cubic phase Cs₂AgInCl₆ DP nanocrystals. Our study clarified the basic structural-optical correlation of halide DPs and may promote their application in related fields.