Photon-Induced Electron Transfer in Ligand-Stabilized Monoclinic CsPbBr₃and Alanine-Functionalized Graphene Heterostructures

In the field of catalysis and energy applications, heterostructures of halide perovskite nanocrystals (NCs) and functionalized graphene are emerging as promising materials. In such heterostructures, it is critical to gain insights into the knowledge that governs the charge and energy transfer dynamics between the components of the heterostructures because it directly affects the efficiency of devices. In this work, we present heterostructures that consist of mercaptoacetic acid (MAA)-functionalized CsPbBr3 NCs and alanine-functionalized graphene. The surface functionalization of CsPbBr3 NCs and graphene enables an effective attachment of the NCs and graphene. The use of MAA as a functionalizing ligand not only passivates the surface of NCs but also provides the possibility of tuning the size of NCs and further coupling with alanine-functionalized graphene. Varying the amount of MAA allows us to synthesize the brightest CsPbBr3 NCs with an absolute photoluminescence quantum yield (PLQY) of 49% and an emission spectral width of 25 nm. By combining alanine-functionalized graphene, the photoluminescence (PL) quenching of the NCs is observed. The photoexcited electron transfer from NCs to alanine-functionalized graphene is responsible for the occurrence of PL quenching that is advocated by time-resolved photoluminescence (TRPL) studies and cyclic voltammetry (CV) analysis. Our work provides a method to control the energetics and analyze the types of charge transfer in functionalized perovskite NCs and graphene heterostructures and motivates further research about the basic knowledge of charge transfer in functionalized donor-acceptor heterostructures.