Sensitive, High‐Speed, and Broadband Perovskite Photodetectors with Built‐In TiO<sub>2</sub> Metalenses
Ting Xiao, Jie Zhao, Peng Sun, Peng Li, Yaokang Zhang, Ni Zhao, Zhiwei Ren, Gang Li, Zhifeng Huang, Zijian Zheng
Abstract
Abstract Monolithic integration of nanostructured metalenses with broadband light transmission and good charge transport can simultaneously enhance the sensitivity, speed, and efficiency of photodetectors. The realization of built‐in broadband metalenses in perovskite photodetectors, however, has been largely challenged by the limited choice of materials and the difficulty in nanofabrication. Here a new type of broadband‐transmitting built‐in TiO 2 metalens (meta‐TiO 2 ) is devised, which is readily fabricated by one‐step and lithograph‐free glancing angle deposition. The meta‐TiO 2 , which comprises of sub‐100 nm TiO 2 nanopillars randomly spaced with a wide range of sub‐wavelength distances in 5–200 nm, shows high transmittance of light in the wavelength range of 400–800 nm. The meta‐TiO 2 also serves as an efficient electron transporting layer to prevent the exciton recombination and facilitate the photoinduced electron extraction and transport. Replacing the conventional mesoporous TiO 2 with the meta‐TiO 2 comprehensively leads to enhancing the detection speed by three orders of magnitude to a few hundred nanoseconds, improving the responsivity and detectivity by one order of magnitude to 0.5 A W −1 and 10 13 Jones, respectively, and extending the linear dynamic range by 50% to 120 dB.