Metal halide perovskites (MHPs) have shown great potential for direct X-ray detection, but achieving high sensitivity without external bias remains challenging. Chiral-polar alternating cation intercalation (ACI)-type MHPs, with excellent optoelectronic properties and a robust chirality-induced bulk photovoltaic effect (BPVE), offer a promising platform for self-driven X-ray detection. Herein, impressive self-driven X-ray detection performance was achieved by utilizing chiral-polar 2D ACI-type perovskite single crystals of (R-PPA)PAPbBr 4 (1R; R-PPA = R-1-phenylpropylamine; PA = propylamine). The chiral R-PPA cations induce the crystallization of 1R in the chiral-polar space group P2 1 , wherein its spontaneous electric polarization further induces a strong BPVE. Consequently, 1R shows remarkable radiation photovoltaics of 0.75 V, which endows its excellent self-driven X-ray detection with a high sensitivity of 417.2 μC Gy −1 cm −2 and a low detection limit of 24.1 nGy s −1 , meeting the state-of-the-art level by leveraging its intrinsic photovoltaic effect. These findings highlight the huge potential of chiral-polar ACI-type MHPs in self-driven X-ray detection applications. D irect X-ray detectors hold tremendous potential in various fields such as medical diagnosis, nondestructive product testing, and fundamental scientific research due to their superior photoelectric conversion efficiency, detection sensitivity, as well as the advantages of miniaturization and integration. 1−5 Nowadays, commercially available semiconductor materials for direct X-ray detection primarily consist of inorganic materials, such as crystalline Si, 6 amorphous Se, 7,8 and Cd(Zn)Te, 9,10 which still face challenges in terms of limited performance and complex manufacturing techniques. Recently, metal halide perovskites (MHPs), as an emerging family of semiconductor materials, hold promising prospects for high-performance X-ray detection due to their strong X-ray absorption from heavy atoms, high carrier mobility−lifetime (μτ) product, and low-cost preparation process. 11 Numerous classic MHPs have achieved impressive performance in direct X-ray detection. 12−15 For instance, Wei et al. reported the first sensitive X-ray detector made of MAPbBr 3 (MA = methylamine) single crystals (SCs), achieving a sensitivity of 80 μC Gy −1 cm −2 at an electric field of 10 V μm −1 . 14 More recently, Song et al. achieved a sensitivity of 5.2 × 10 6 μC Gy −1 cm −2 using an MAPbI 3 SC device under a high electric field of 1000 V cm −1 . 16 Despite such progress, most reported MHPs detectors still rely on external electrical fields to separate and transport the radiation-generated carriers, achieving height-ened sensitivity at the expense of employing sizable electric fields, thereby leading to significant energy consumption and overall circuitry volume expansion. 11,17−20 Additionally, the amplification of noise currents occurs under external biases, which hampers the detection of low-dose X-rays. Therefore, developing X-ray detectors that can operate w...
