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 Sn²⁺ ions in precursor solutions. It is discovered that the oxidation of Sn²⁺ to Sn⁴⁺ ions not only consumes Sn²⁺ 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 (H₃PO₂), high-quality Sn-Pb perovskite SCs can be robustly grown in ambient air with low trap density of 6.58 × 10⁹ cm⁻³ and high carrier mobility-lifetime product (µτ) of 1.5 × 10⁻³ cm² 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 × 10¹⁰ Jones.