Ion Migration as a New Paradigm to Boost Self‐Driven Perovskite Narrowband Photodetectors

Abstract Halide perovskite narrowband photodetectors based on a charge collection narrowing mechanism have emerged as a new class of optoelectronic devices for monochromatic imaging. However, improving the figures‐of‐merit of such narrowband photodetectors remains challenging due to the inability to manipulate the major material players in the elusive photoresponse process. Here, a novel approach of manipulating ion migration to enhance the narrowband photoresponse of self‐driven p‐i‐n type photodetectors is taken by intentionally adding mobile ions into the formamidine and methylamine mixed cation perovskite layer. The excess mobile ions reduce the activation energy of ion migration, and this facilitated migration orchestrates the ions in the perovskite layer to re‐engineer the energy band, and thus modulates the charge separation and collection energetics and kinetics, leading to an unprecedented boost of the narrowband photoresponse. The photodetector based on this approach achieved a peak responsivity of as high as 112.41 mA W⁻¹ at 820 nm at zero bias with a full‐width at half maximum of only 22 nm and an over 3‐fold improvement in the spectral rejection ratio, making it highly promising for the next‐generation color imaging devices.