Effect of thickness on the electronic structure and optical properties of quasi two-dimensional perovskite CsPbBr3 nanoplatelets

The effect of thickness of cesium lead halide perovskite CsPbBr3 nanoplatelets (NPLs) on their electronic structure and optical properties are investigated using an effective-mass envelope function theory based on the 8band k.p model with the consideration of exciton binding energy. We first reported the CsPbBr3 nanoplatelets' band structure and optical gain with exciton effect. As the thickness of NPLs decreases, their bandgap increases and the band mixing is more obvious which influences the transition matrix element (TME). The optical gain of CsPbBr3 nanoplatelets is calculated by taking into account of TME, Fermi factor, injected carrier density and thickness. A blue shift of peak position in optical gain can be observed as the thickness of NPLs decreases. As the injected carrier density arises, the maximum optical gain of thicker NPLs reach saturation much faster than the thinner ones. To obtain high differential gain, NPLs with less thickness are better choices. Experimental work is carried out and the results agree with our theoretical results very well.