Overcoming spectral limits of perovskite photodetectors for the infrared region

Extending the spectral response of metal halide perovskites into the infrared (IR) regime is a critical challenge constrained by intrinsic bandgap limits. This review surveys strategies to surmount this barrier for high‐performance IR photodetectors. We first examine single‐crystal approaches that exploit sub‐bandgap trap states and impurity‐level engineering. Next, we discuss polycrystalline thin films where mixed Sn‐Pb compositions, defect passivation and additive engineering have proven effective. The review then covers micro‐ and nano‐structured architectures that enhance light‐matter interactions. Subsequently, we analyze heterojunctions that combine perovskites with elemental semiconductors, inorganic compounds, organic semiconductors, or other perovskite phases. We also explore hybrid systems incorporating functional materials such as organic dyes, quantum dots and carbon nanotubes. Alternative mechanisms, including upconversion, two‐photon absorption and bolometric effects, are also highlighted. Despite notable advances extending the cut‐off wavelength up to 4000 nm, a persistent trade‐off remains among spectral breadth, sensitivity, response speed, and device stability. Finally, four future directions are identified: extending the cutoff wavelength beyond the short‐wave infrared region, improving infrared responsivity and detectivity, expanding functionality beyond conventional intensity detection and enhancing long‐term operational stability. This review aims to provide a clear roadmap for transitioning from material‐centric to function‐centric design, guiding the development of next‐generation perovskite IR photodetectors for applications ranging from biomedical imaging to optical communication.