Self-Powered\nBroadband Photodetection Ranging from\nX‑ray to UV–Vis Light in a Polar Perovskite Induced\nby Bulk Photovoltaic Effect

Self-powered broadband photodetection has evoked increased\ninterest\nin next-generation photoelectronic devices. However, realizing self-powered\nbroadband photodetection in a single material is still a challenge\nbecause of the harsh requirements, including powerful built-in field,\nexcellent charge transport behaviors, as well as the broad absorption.\nHerein, we first realize broadband photodetection in the range from\nX-ray to UV–vis light in a polar two-dimensional perovskite\n(2-FBA)<sub>2</sub>MAPb<sub>2</sub>I<sub>7</sub> (2-FBA = 2-fluorobenzylamine,\nMA = methylamine) by incorporating an aromatic spacer into a three-dimensional\nprototype. As a result, (2-FBA)<sub>2</sub>MAPb<sub>2</sub>I<sub>7</sub> exhibited a superior response to UV–vis light (377 to 637\nnm) without voltage bias. Specifically, a high switching ratio of\n1.05 × 10<sup>4</sup>, an outstanding responsivity (<i>R</i>) of 1420 mA W<sup>–1</sup>, and detectivity (<i>D</i>*) of 1.59 × 10<sup>13</sup> Jones were achieved under light\nillumination at 520 nm. Moreover, (2-FBA)<sub>2</sub>MAPb<sub>2</sub>I<sub>7</sub> achieved a high sensitivity of 46.4 μC Gy<sup>–1</sup> cm<sup>–2</sup> without voltage bias, two\ntimes higher than that of a commercial α-Se film detector (20\nμC Gy<sup>–1</sup> cm<sup>–2</sup>). The sensitivity\ncan be further improved to 3316 μC Gy<sup>–1</sup> cm<sup>–2</sup> at a 50 V bias. These results give insight into the\ndesign of 2D perovskites for self-powered broadband photodetection.