Donor/Acceptor Charge-Transfer States at Two-Dimensional Metal Halide Perovskite and Organic Semiconductor Interfaces

Metal halide perovskite semiconductors with small exciton binding energy have been widely used in perovskite solar cells and achieved rapid progress in terms of device performance. However, the strong excitonic nature of two-dimensional (2D) perovskites with small n values remains underexploited (n represents the number of inorganic monolayer sheets sandwiched between bulky organic cation layers). In this work, we report experimental evidence of donor/acceptor charge-transfer (CT) states formed at 2D metal halide perovskite/organic semiconductor heterojunctions, with a corresponding increase in photocurrent production for these excitonic materials. Furthermore, it is found that the size of the organic cation in the 2D perovskite layer plays a critical role in the CT process. The ability to dissociate excitons in 2D perovskites by interfacing with an organic semiconductor in a donor/acceptor configuration opens up new opportunities for exploiting the excitonic nature of low-dimensional perovskites in appli...