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

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.