Controllable Regulation of Inorganic‐Layer Thickness of Polar 2D Homologue Perovskites toward Self‐Powered Polarization‐Sensitive Photodetection

Abstract Polarization‐sensitive photodetection has intensive practical applications, including optical anti‐counterfeiting, image encryption, and remote sensing. 2D hybrid perovskites have emerged as a robust candidate in this portfolio, due to their inherent quantum‐confined structure and anisotropic properties. However, studies on the chemical assembly of inorganic‐layer thickness to regulate structural anisotropy and polarization‐sensitive photodetection behavior remain insufficient. Here, the inorganic‐layer thickness of 2D homologous perovskites is regulated, (MBA)₂(CH₃NH₃)_n−1Pb_nI_3n+1 (n = 1–3, where MBA = 4‐methylbenzylamine), featuring the similar polar structures and strong optical anisotropy. Notably, photoelectric merits are greatly improved from n = 1 to n = 3 with the weakening of the quantum confinement effect. Under illumination, the n = 3 member exhibits large on/off ratios of photocurrent (≈2.1 × 10⁴) far beyond other lower‐layered counterparts. The polarized‐light photodetector based on n = 3 crystal shows intriguing behaviors, including noticeable responsivity (1.2 mA W⁻¹), detectivity (9.5 × 10¹³ Jones), and superior photocurrent anisotropy (≈110.4). Besides, fascinating self‐powered polarization behaviors with a large anisotropy contrast are achieved based on the bulk photovoltaic effect, stemming from the structural polarity. These characteristics underscore the design strategy of inorganic‐layer regulation in advancing the exploration of new 2D perovskite candidates for polarization‐based optoelectronics.