Enhanced Optical Absorption and Interfacial Carrier Separation of CsPbBr3/Graphene Heterostructure: Experimental and Theoretical Insights

Controlling effective separation of carriers at the interface is a key element to realize highly efficient halogenated perovskite-based optoelectronic devices. Here, a comprehensive study of interfacial properties for CsPbBr3 nanocrystals (NCs)/graphene heterostructure is performed by the combination of theoretical and experimental methods. Enhanced visible light absorption is observed experimentally in the CsPbBr3 NCs/graphene heterostructure. The strong photoluminescence quenching phenomenon and improved photoresponse prove the efficient interfacial charge transfer from the perovskite CsPbBr3 NC layer to the graphene side. Significantly, theoretical calculations suggest that an intrinsic built-in electric field, pointing from graphene toward CsPbBr3, promotes the separation of photoinduced carriers at the CsPbBr3 NCs/graphene interface and simultaneously inhibits the recombination of electron-hole pairs. Thus, the high optoelectronic performance can be obtained in the CsPbBr3 NCs/graphene heterostructure, as shown in our experiment. Moreover, the CsPbBr3 NCs/graphene heterostructure exhibits smaller effective mass than that of CsPbBr3 NCs, indicating that the heterostructure does possess a high carrier mobility, which can further accelerate the separation of photogenerated carriers. Furthermore, the calculated results reveal that, accounting for the presence of the stronger built-in electric field, larger band bending value, and smaller effective mass, the PbBr2/graphene interface can realize the separation of the photoinduced carriers more effectively than the CsBr/graphene interface and thus more efficiently facilitate electron transfer from the perovskite optical absorber side to the graphene electronic transport side. Our findings provide valuable insight into perovskite/graphene-based photodetector devices via the interface engineering project.