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Interlayer excitons (IXs) are demonstrated in two‐dimensional (2D) perovskite/transition‐metal dichalcogenide (TMD) heterostructures regardless of the lattice match, momentum mismatch, and thermal annealing processes. The broad selection of 2D perovskites and TMDs together with the robust interlayer coupling between constituent layers make 2D perovskite/TMD heterostructures an attractive platform for studying IXs. However, studies on IXs in 2D perovskite/TMD heterostructures are still in their infancy, and how the organic cation affects the IXs in 2D perovskite/TMD heterostructures remains elusive. Herein, this article reports on IXs emission from heterostructures consisting of monolayer WSe2 and 2D perovskites with different organic cations. Notably, by temperature‐dependent photoluminescence studies on (EA)2PbI4/WSe2 and (PEA)2PbI4/WSe2 heterostructures (EA = ethylamine and PEA = phenylethylammonium), it is found that the organic cations of 2D perovskites can effectively change the exciton binding energy of the IXs and thus the emission peak of the IXs. The observed difference can be ascribed to the significant dielectric constant difference between their organic cations. Furthermore, the change in the organic cations can also affect the dipole–dipole interaction and lifetime of IXs. The findings provide critical insights into the 2D perovskite/TMD heterointerfaces and also open up new opportunities for exploiting tunable exciton devices based on IXs. [ABSTRACT FROM AUTHOR]

Solution‐processable organic–inorganic hybrid perovskite materials have been applied to a variety of optoelectronic devices due to its long exciton lifetime and small binding energy. It has emerged as promising front‐runners for next‐generation non‐volatile flash photomemory devices. However, the effect of crystal orientation of perovskite on the performance of photomemory still has not fully developed. Herein, non‐volatile flash photomemory with quasi‐2D perovskite/polystyrene‐block‐poly(ethylene oxide) (PS‐b‐PEO) as photoactive floating‐gate and p‐type semiconductor poly(3‐hexylthiophene‐2,5‐diyl) (P3HT) as the chare‐transporting layer is successfully demonstrated. By adding phenylethylammonium bromide (PEABr) in formamidinium lead bromide perovskite (FAPbBr3), the crystal orientation of quasi‐2D perovskite is highly improved, which results in raised charge transfer efficiency from 76% to 90% compared to the pure FAPbBr3. Furthermore, ON/OFF current ratio of 104, low photo‐programming time of 5 ms under light intensity of 0.85 mW cm−2, charge transfer rate of 0.063 ns−1, and data storage capacity of over 7 bits (128 levels) in one cell can be achieved. In addition, the correlation between photo‐responsive current and photoluminescence (PL) is first examined by in operando PL measurement, which provides a new platform to explore the charge transfer process in photomemory. [ABSTRACT FROM AUTHOR]