Harnessing the Pyro‐Phototronic Effect in Benzimidazolium Bismuth Bromide Perovskites for Enhanced Photodetection

Organic–inorganic halide perovskites (OIHPs) exhibit strong light–matter coupling and polarization‐assisted charge transport, making them promising for multifunctional optoelectronics. The pyro‐phototronic effect (PPE) linking photoinduced thermal excitation with polarization‐driven carrier separation enhances photodetection sensitivity but is typically restricted to non‐centrosymmetric materials with intrinsic polarization. Here, we demonstrate a pronounced PPE in a centrosymmetric, lead‐free benzimidazolium bismuth bromide perovskite, (Benz) 4 Bi 2 Br 10 (BBB) with an optical bandgap of 2.66 eV. Single‐crystal X‐ray diffraction confirms a monoclinic P2 1 /c phase with locally distorted [Bi 2 Br 10 ] 4 − octahedra. Piezoresponse force microscopy (PFM) reveals nanoscale polarization domains, while conductive atomic force microscopy (C‐AFM) and Kelvin probe force microscopy (KPFM) analyses confirm efficient p‐type transport and a high work function of 4.98 eV. Additionally, we have measured KPFM surface potential with variation of positive and negative voltages to further support nanoscale localized polarization. Photodetectors fabricated on interdigitated electrodes exhibit the distinct four‐stage transient signature of the PPE under 450–600 nm illumination and maintain excellent stability over 1800 on/off cycles. The response originates from interfacial polarization at the organic–inorganic boundary, which governs carrier separation and transport. These findings identify BBB as a stable, lead‐free perovskite platform where interfacial polarization enables efficient and broadband pyro‐phototronic photodetection.