Enhanced Interfacial Exciton Transport in Mixed 2D/3D Perovskites Approaching Bulk 3D Counterparts

Mixed 2D/3D halide perovskites possess unique optoelectronic properties and strong structural stability, making them promising for various light-harvesting and -emitting applications. However, the long-chain organic cations have low charge conductivity and create potential barriers within the inorganic frameworks, which limit efficient exciton and carrier transport. In this study, we propose a method to improve exciton transport in 2D/3D perovskites by adjusting the conjugation interactions of long-chain ligands. Through time-resolved spectroscopy and high-resolution transmission electron microscopy, we establish the relationship between the microstructure of 2D/3D perovskites and exciton mobility. We successfully create a 2D/3D halide perovskite film with an exciton transport value of 92 cm² V^-1 s^-1, approaching its 3D bulk counterparts. We explain that the strong interligand conjugation of the naphthylmethylammonium cation aids in forming a 2D phase with a small <n> value, which compresses the 2D domains to the nanometer scale, thereby enhancing carrier tunneling and exciton mobility across the 3D grain boundaries. These findings offer helpful perspectives for the development of high-mobility mixed 2D/3D perovskite films for applications in solar cells, light-emitting diodes, and photodetectors.