We developed a transverse photodetector using EA4Pb3Br10 films that demonstrates excellent self-powered performance: a responsivity (R) of 0.11 A W−1 and a detectivity (D*) of 1.41 × 109 Jones. At 3.0 V bias, performance enhances dramatically (R = 11.40 A W−1, D* = 1.42 × 1011 Jones). Excitation intensity-dependent transient absorption measurements reveal a carrier diffusion length of ∼2.90 μm, accounting for the superior optoelectronic performance. Frequency-modulation tests demonstrate the bias voltage effectively aligns ferroelectric domains, thereby restricting the barrier associated with crystal domains and resulting in significantly faster response times than those under self-powered operation. The implemented encrypted optical communication system operates reliably in power-scarce environments; meanwhile, our single-pixel imaging system, which functions without an external power, is also designed. Both of them are suitable for responding to sudden power outages in emergency scenarios. This work advances the field of high-performance photodetection while expanding practical optoelectronic applications.