Composition‐Dependent Hot Carrier Relaxation Dynamics in Cesium Lead Halide (CsPbX3, X=Br and I) Perovskite Nanocrystals

Cesium‐based perovskite nanocrystals (NCs) have outstanding photophysical properties improving the performances of lighting devices. Fundamental studies on excitonic properties and hot‐carrier dynamics in perovskite NCs further suggest that these materials show higher efficiencies compared to the bulk form of perovskites. However, the relaxation rates and pathways of hot‐carriers are still being elucidated. By using ultrafast transient spectroscopy and calculating electronic band structures, we investigated the dependence of halide in Cs‐based perovskite (CsPbX3 with X=Br, I, or their mixtures) NCs on the hot‐carrier relaxation processes. All samples exhibit ultrafast (CsPbBr1.5I1.5 (380 fs)>CsPbI3 NC (580 fs). These result accounts for a reduced light emission efficiency of CsPbI3 NC compared to CsPbBr3 NC. Heiße Träger: Die signifikante Abhängigkeit der Relaxationsrate heißer Träger vom Halogen (X=Br, I oder Mischung) wird hauptsächlich der Zustandsdichte der Löcher im Valenzband von CsPbX3‐Nanokristallen zugeordnet. Die Relaxationsrate verringert sich beim Übergang von CsPbBr3‐ zu CsPbI3‐Nanokristallen. VB=Valenzband, CB=Leitungsband.