Paper-Based Stable Broad Band Optical Detector Made from Mixed Cation Organic Perovskite Halides

We report a paper-based photodetector made from mixed cation organic perovskite halide MA_1–<i>x</i>FA<i>_x</i>PbI₃ (MA = methylammonium (CH₃NH₃); FA = formamidium CH­(NH₂)₂). The detector shows a substantial photogain and photoresponse at low illumination intensity (<10 μW/cm²) and a broad band response that extends from 300 to 800 nm at the optimum substitutional level with <i>x</i> = 0.4. A peak responsivity of 0.27 A/W in the paper photodetector was observed at a wavelength of ∼775 nm at a bias of 5 V. The responsivity stayed above 0.1 A/W for a broad optical wavelength range of 550 to 825 nm that covers a good range of the visible spectra. The detector has a low dark current (<10^–9 A) at highest bias of operation and an rms current noise of ≤10 pA. The mixed halide detector was grown on conventional paper using a one-pot chemical process. The detector reported here is stable at a room ambience and does not deteriorate under prolonged exposure to illumination. It combines the high response of MAPbI₃ and the stability of FAPbI₃. The paper photodetector is useful in a number of applications needing flexible and disposable detectors, and the power requirement even at full operation is <0.5 μW at a low bias (<5 V) making it compatible with battery-powered operation.