Correlated Dynamics of Free and Self‐Trapped Excitons and Broadband Photodetection in BEA2PbBr4 Layered Crystals

Abstract Self‐trapped excitons (STEs) exert a profound impact on the optical properties and device applications of 2D halide perovskites. Particularly distinct exciton self‐trapping and detrapping processes can facilitate the intelligent design of perovskite optoelectronic devices with emerging functionalities. Thus, a comprehensive understanding and regulation of exciton trapping and detrapping dynamics are highly desired. Herein, the authors report a 2D lead halide perovskite (BEA 2 PbBr 4 where BEA is 2‐bromine ethylamine) with exceptional broadband photoluminescence (PL), which originates from multiple STE states. In particular, the unique energy‐level configuration of STEs with respect to free excitons is revealed by exploiting optical spectroscopy. Consequently, these distinct phenomena empower the broadband photodetection capability of BEA 2 PbBr 4 photodetectors over a wide range from ultraviolet to near‐infrared wavelengths. These results provide an essential understanding of the intriguing photophysics of STEs and shed new light on the future development of single‐component perovskite broadband optoelectronic devices.