2D Behaviors of Excitons in Cesium Lead Halide Perovskite\nNanoplatelets

Abstract

Fundamental\nto understanding and predicting the optoelectronic\nproperties of semiconductors is the basic parameters of excitons such\nas oscillator strength and exciton binding energy. However, such knowledge\nof CsPbBr₃ perovskite, a promising optoelectronic material,\nis still unexplored. Here we demonstrate that quasi-two-dimensional\n(quasi-2D) CsPbBr₃ nanoplatelets (NPLs) with 2D exciton\nbehaviors serve as an ideal system for the determination of these\nparameters. It is found that the oscillator strength of CsPbBr₃ NPLs is up to 1.18 × 10⁴, higher than that\nof colloidal II–VI NPLs and epitaxial quantum wells. Furthermore,\nthe exciton binding energy is determined to be of ∼120 meV\nfrom either the optical absorption or the photoluminescence analysis,\ncomparable to that reported in colloidal II–VI quantum wells.\nOur work provides physical understanding of the observed excellent\noptical properties of CsPbBr₃ nanocrystals and would benefit\nthe prediction of high-performance excitonic devices based on such\nmaterials.