Filterless Near‐Infrared Narrowband Photodetectors Based on Mixed Metal Perovskite Single Crystals

Iodine‐based Sn‐Pb mixed perovskite single crystals (SCs) are promising candidates for near‐infrared (NIR) narrowband photodetectors due to their low bandgaps. However, they are highly defective when grown in ambient air due to the extremely poor air stability of Sn 2+ ions in precursor solutions. It is discovered that the oxidation of Sn 2+ to Sn 4+ ions not only consumes Sn 2+ ions but also increases the precursor solution viscosity. The increased viscosity slows down the solute diffusion and hinders the anisotropic growth of SCs, leading to Sn‐Pb perovskite SCs with curved convex surfaces and unevenly distributed composition. By preventing the solute‐diffusion‐limited growth mode with hypophosphorous acid (H 3 PO 2 ), high‐quality Sn‐Pb perovskite SCs can be robustly grown in ambient air with low trap density of 6.58 × 10 9 cm −3 and high carrier mobility‐lifetime product ( µτ ) of 1.5 × 10 −3 cm 2 V −1 . Accordingly, a series of filterless NIR narrowband photodetectors with gradually tuned detection centers and dual detection modes has been achieved, delivering a maximum external quantum efficiency of 15.2% and detectivity of 1.19 × 10 10 Jones.