Enhancing Carrier Transport in 2D/3D Perovskite Heterostructures through Organic Cation Fluorination

The interfacial 2D/3D perovskite heterostructures have attracted extensive attention due to their unique ability to combine the high stability of 2D perovskites with the remarkable efficiency of 3D perovskites. However, the carrier transport mechanism within the 2D/3D perovskite heterostructures remains unclear. In this study, the carrier transport dynamics in 2D/3D perovskite heterostructures through a variety of time-resolved spectroscopic measurements is systematically investigated. Time-resolved photoluminescence results reveal nanosecond hole transfer from the 3D to 2D perovskites, with enhanced efficiency through the introduction of fluorine atoms on the phenethylammonium (PEA) cation. Transient absorption measurements unveil the ultrafast picosecond electron and energy transfer from 2D to 3D perovskites. Furthermore, it is demonstrated that the positioning of fluorination on the PEA cations effectively regulates the efficiency of charge and energy transfer within the heterostructures. These insightful findings shed light on the underlying carrier transport mechanism and underscore the critical role of cation fluorination in optimizing carrier transport within 2D/3D perovskite heterostructure-based devices.