Ultrafast Carrier Transfer Promoted by Interlayer Coulomb Coupling in 2D/3D Perovskite Heterostructures

Engineering 2D-structured lead halide perovskites leads to both excellent optoelectronic performance and intriguing photophysics. Here, the underlying mechanisms of exciton interaction and carrier transfer in 2D/3D hybrid perovskites are studied. The investigated perovskites are in the form of self-assembled microplatelets, which are naturally composed of multiple perovskite phases, with n being 1, 2, 3, or 4 or nanocrystals in bulk phase (n approximate to infinity). Excitonic energy transfer and charge separation between different phases are found to coexist in this hybrid system, which occur at an ultrafast timescale (<100 fs) followed by a relatively slow channel (2-15 ps). The experimental results reveal that this hybrid perovskite naturally forms a series of heterostructures, with excitons generated in different phases, showing Coulomb interactions across the interface. This interlayer Coulomb coupling should account for the aforementioned ultrafast carrier transfer. This work provides an accurate and thorough explanation for the remarkable charge transfer rate, which is extremely beneficial for their applications in photovoltaic and optoelectronic devices, even with the apparent interfacial scattering, defect trapping, and disorder-induced exciton localization in 2D/3D hybrid perovskites.