High-Performance Photodiode-Type Photodetectors Based on Polycrystalline Formamidinium Lead Iodide Perovskite Thin Films

Photodetectors based on three dimensional organic–inorganic lead halide perovskites have recently received significant attention. As a new type of light-harvesting materials, formamidinium lead iodide (FAPbI3) is known to possess excellent optoelectronic properties even exceeding those of methylammonium lead iodide (MAPbI3). To date, only a few photoconductor-type photodetectors based on FAPbI3 single crystals and polycrystalline thin films in a lateral structure have been reported. Here, we demonstrate low-voltage, high-overall-performance photodiode-type photodetectors in a sandwiched geometry based on polycrystalline α-FAPbI3 thin films synthesized by a one-step solution processing method and post-annealing treatment. The photodetectors exhibit a broadband response from the near-ultraviolet to the near-infrared (330–800 nm), achieving a high on/off current ratio of 8.6 × 104 and fast response times of 7.2/19.5 μs. The devices yield a photoresponsivity of 0.95 AW−1 and a high specific detectivity of 2.8 × 1012 Jones with an external quantum efficiency (EQE) approaching 182% at −1.0 V under 650 nm illumination. The photodiode-type photodetectors based on polycrystalline α-FAPbI3 thin films with superior performance consequently show great promise for future optoelectronic device applications.