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High‐performance light‐emitting/detecting bifunctional optoelectronic devices based on halide perovskites are hindered by the less efficient carrier transport and radiative recombination processes. The density of defects (i.e., surface and bulk defects) is the main factor affecting carrier transport, radiation recombination, and determining performance in perovskites. Therefore, techniques to effectively regulate defects are highly needed. Here, a convenient and effective strategy, electrical doping, is proposed to flexibly regulate defect density, resulting in dramatically enhanced light‐emitting (i.e., fluorescence and carrier lifetime) and light‐detecting performance (i.e., hole mobility, photo‐responsivity, and photo‐detectivity) simultaneously. An improved carrier transport model in CH3NH3PbBr3 (MPB) single‐crystal thin‐film (SCTF) is proposed to elucidate the regulation mechanism of defects and carrier transport under electrical doping. These results show that the surface defect density can be effectively reduced by 47.49% under optimal electrical poling intensity (0.168 V µm−1), and photoluminescence intensity and carrier lifetime can be increased by 259% and 89.98%, respectively. Furthermore, planar MPB SCTF photodetector exhibits hole mobility increased by 14.97%, photo‐responsivity increased by 82.78%, and photo‐detectivity increased by 868% at 0.168 V µm−1. Particularly, a record photo‐detectivity of 3.53 × 1013 Jones is achieved under electrical doping. This study provides guidance for flexibly adjusting defect density and optimizing perovskite SCTFs light‐emitting/detecting bifunctional devices. [ABSTRACT FROM AUTHOR]