Modulating the Photoresponsivity of Perovskite Photodetectors through Interfacial Engineering of Self‐Assembled Monolayers

Abstract Photodetectors are one of the most essential optoelectronics nowadays. Perovskites have emerged as one of the potential materials for photodetectors due to their high absorption efficiency over a wide range of wavelengths, high charge mobility, strong mechanical deformability, and solution processability. In this study, interfacial engineering using self‐assembled monolayers (SAMs) is explored to improve the performance of perovskite photodetectors. SAMs with different terminal groups exhibit distinct surface energy, and they all result in a reduced exciton lifetime of the perovskite due to charge transfer between polycrystalline perovskite and the SAMs. In particular, the photodetector modified with (4‐hydroxyphenyl)phosphonic acid (OH) exhibits the highest electron mobility of 0.8 cm² V⁻¹ s⁻¹ under 450‐nm light illumination. In addition, it shows excellent detector performance with an ultrafast photoresponse of < 14 ms, a high photoresponsivity of 5600 AW⁻¹, and a high specific detectivity of 5.9 × 10¹⁰ Jones at a low light intensity of 18 µW cm⁻². The excellent photoresponse and device switchability are attributed to the high surface energy of OH, the resulting homogeneous perovskite film morphology, the high charge transfer efficiency, and the favorable energy level alignment. The studies provide new prospects for the development of emerging perovskite photodetectors.