Room-Temperature Solution-Processed NiO_x: PbI₂ Nanocomposite Structures for Realizing High-Performance Perovskite Photodetectors

While methylammonium lead iodide (MAPbI₃) with interesting properties, such as a direct band gap, high and well-balanced electron/hole mobilities, as well as long electron/hole diffusion length, is a potential candidate to become the light absorbers in photodetectors, the challenges for realizing efficient perovskite photodetectors are to suppress dark current, to increase linear dynamic range, and to achieve high specific detectivity and fast response speed. Here, we demonstrate NiO_x:PbI₂ nanocomposite structures, which can offer dual roles of functioning as an efficient hole extraction layer and favoring the formation of high-quality MAPbI₃ to address these challenges. We introduce a room-temperature solution process to form the NiO_x:PbI₂ nanocomposite structures. The nanocomposite structures facilitate the growth of the compact and ordered MAPbI3 crystalline films, which is essential for efficient photodetectors. Furthermore, the nanocomposite structures work as an effective hole extraction layer, which provides a large electron injection barrier and favorable hole extraction as well as passivates the surface of the perovskite, leading to suppressed dark current and enhanced photocurrent. By optimizing the NiOx:PbI2 nanocomposite structures, a low dark current density of 2 × 10^–10 A/cm² at −200 mV and a large linear dynamic range of 112 dB are achieved. Meanwhile, a high responsivity in the visible spectral range of 450–750 nm, a large measured specific detectivity approaching 10¹³ Jones, and a fast fall time of 168 ns are demonstrated. The high-performance perovskite photodetectors demonstrated here offer a promising candidate for low-cost and high-performance near-ultraviolet–visible photodetection.