Enhanced Performances of Photodetectors by Reducing Light Reflection Based on Two-Dimensional CsPbBr₃ Composite Structures

Two-dimensional (2D) perovskites have been widely applied in photoelectric devices due to their excellent optical and electrical properties. However, the low optical absorption of their ultrathin thickness inhibits photoelectron generation and thus limits their performances. Herein, we constructed 2D CsPbBr3 devices of composite structures by combining them with g-C3N4 (CN) and graphene oxide (GO). As compared to CsPbBr3 devices, the photocurrents of GO/CsPbBr3 and CN/CsPbBr3 devices increase by 68 and 114%, respectively. Based on experimental spectra in combination with the finite-element method (FEM), the reflectivity values of GO/CsPbBr3 and CN/CsPbBr3 devices are, respectively, reduced by 21 and 33%, and therefore absorption coefficients are increased by 18 and 28%, respectively, and the corresponding internal quantum efficiencies are increased by 63 and 96%, respectively, in comparison to the CsPbBr3 devices. Furthermore, we have quantitatively determined the linear relationship between the absorption coefficient and the photocurrent based on the diffusion theory of semiconductors. A general approach for improving the optoelectronic performance can be extended to other devices by constructing composite structures with strong photon absorption and low reflection.