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

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.