High-Performance Perovskite Photodetectors with Suppressed Dark Current Density via Small Molecule in Antisolvent Strategy

Dark current density, a critical parameter in perovskite photodetectors (PPDs), largely depends on the quality of the perovskite film. Herein, we introduce a new small molecule in antisolvent strategy to enhance perovskite film quality during the crystallization of Cs_0.05(FA_0.95MA_0.05)_0.95Pb(I_0.95Br_0.05)₃. COTIC-4Cl, an N-type narrow bandgap nonfullerene small molecule with specific functional group, could strongly bind to the uncoordinated Pb²⁺ in the perovskite with assistance of antisolvent, enabling rapid supersaturation of perovskite solution and form dense structures under low-temperature annealing. This strategy leads to the decreased nonradiative recombination and improved carrier transport efficiency in COTIC-4Cl-modified perovskites. The PPDs based on COTIC-4Cl-modified films exhibit a broad spectral response from 300 to 815 nm, an exceptionally low dark current density of 2.17 × 10^-11 A cm^-2, and enhanced detectivities of 1.84 × 10¹⁴and 3.09 × 10¹² Jones at 0 and -0.5 V bias, respectively. Improved responsivity and detectivity at 650-780 nm result from strong near-infrared light absorption by COTIC-4Cl. These optimized PPDs are comparable to commercial silicon photodetectors, promising significant advancements in cost-effective photodetector technology.