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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−1PbnI3n+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. [ABSTRACT FROM AUTHOR]

Bismuth-based halide perovskites have shown great potential for direct X-ray detection, attributable to their nontoxicity and advantages in detection sensitivity and spatial resolution. However, the practical application of such materials still faces the critical challenge of combining both high sensitivity and low detection limits. Here, we report a new type of zero-dimensional (0D) perovskite (HIS)BiI 5 ( 1 , where HIS 2+ = histamine) with high sensitivity and a low detection limit. Structurally, the strong N-H···I hydrogen bonds between HIS 2+ cations and inorganic frameworks enhance the rigidity of the structure and diminish the intermolecular distance between adjacent inorganic [Bi 2 I 10 ] 4- dimers. By virtue of such structural merits, single crystal 1 exhibits excellent physical properties perpendicular to both the (001) and (010) faces. Perpendicular to the (010) face, 1 exhibited a high electrical resistivity (2.31 × 10 11 Ω cm) and a large carrier mobility-lifetime product ( μτ ) (2.81 × 10 -4 cm 2 V -1 ) under X-ray illumination. Benefiting from these superior physical properties, it demonstrates an excellent X-ray detection capability with a sensitivity of approximately 10 3 μC Gy air -1 cm -2 and a detection limit of 36 nGy air s -1 in both directions perpendicular to the (001) and (010) crystal faces. These results provide a promising candidate material for the development of new, lead-free, high-performance X-ray detectors.