High‐Sensitivity Self‐Powered X‐Ray Detectors Based on Chiral Bismuth Perovskites

Lead-free perovskites are emerging as eco-friendly alternatives for X-ray detection, yet achieving high sensitivity, stability, and self-powered operation remains a challenge. Here, we present a 0D chiral organic-inorganic hybrid bismuth perovskite single crystal, (R/S-NEA)₄Bi₂Cl₁₀ (NEA = (2-naphthyl)ethylamine), that enables a bulk photovoltaic effect (BPVE) for efficient, self-powered X-ray detection. Its unique structure, featuring isolated [Bi₂Cl₁₀]4^- dimers within a hydrogen-bonded chiral lattice, facilitates asymmetric charge transport, enhancing intrinsic carrier separation. The resulting detector achieves a record sensitivity of 10 200 µC·Gy^-1 cm^-2 at 1000 V bias and maintains self-powered operation (0 V) with a low detection limit of 510 nGy s^-1, outperforming existing bismuth-based perovskite detectors. Notably, these crystals retain structural integrity for over a year in ambient conditions, while the device exhibits stable operation for over 4000 s under continuous X-ray exposure. This work advances chiral perovskite engineering as a powerful strategy for developing next-generation lead-free X-ray detectors with high performance and long-term durability, making them attractive for portable medical imaging and radiation monitoring.