High-Performance\nPerovskite Photodetectors with Suppressed Dark Current Density via\nSmall Molecule in Antisolvent Strategy

Dark\ncurrent density, a critical parameter in perovskite\nphotodetectors (PPDs), largely depends on the quality of the perovskite\nfilm. Herein, we introduce a new small molecule in antisolvent strategy\nto enhance perovskite film quality during the crystallization of Cs<sub>0.05</sub>(FA<sub>0.95</sub>MA<sub>0.05</sub>)<sub>0.95</sub>Pb(I<sub>0.95</sub>Br<sub>0.05</sub>)<sub>3</sub>. COTIC-4Cl, an N-type narrow\nbandgap nonfullerene small molecule with specific functional group,\ncould strongly bind to the uncoordinated Pb<sup>2+</sup> in the perovskite\nwith assistance of antisolvent, enabling rapid supersaturation of\nperovskite solution and form dense structures under low-temperature\nannealing. This strategy leads to the decreased nonradiative recombination\nand improved carrier transport efficiency in COTIC-4Cl-modified perovskites.\nThe PPDs based on COTIC-4Cl-modified films exhibit a broad spectral\nresponse from 300 to 815 nm, an exceptionally low dark current density\nof 2.17 × 10<sup>–11</sup> A cm<sup>–2</sup>, and\nenhanced detectivities of 1.84 × 10<sup>14</sup>and 3.09 ×\n10<sup>12</sup> Jones at 0 and −0.5 V bias, respectively. Improved\nresponsivity and detectivity at 650–780 nm result from strong\nnear-infrared light absorption by COTIC-4Cl. These optimized PPDs\nare comparable to commercial silicon photodetectors, promising significant\nadvancements in cost-effective photodetector technology.