A thin and flexible scanner for fingerprints and documents based on metal halide perovskites

Solution-processed photodetectors could be of use in large-area light-sensing applications because they can be fabricated at low cost on plastic substrates and their absorption spectra can be tuned by chemical design. However, fabricating photodetectors with low dark currents and integrating them into high-resolution backplanes remains challenging. Here we show that solution-processed metal halide perovskite photodiodes on top of an amorphous indium gallium zinc oxide transistor backplane can be used to create a flexible image sensor that is ~100 μm thick and has a resolution of 508 pixels per inch. We have developed a pixel edge cover layer for the system that reduces electrode current leakage and thus dark current density. The low noise current in combination with high external quantum efficiency results in high photodetectivity at wavelengths from 550 nm to 770 nm. We show that our imager can be used for document scanning and biometric fingerprinting and that it can be wrapped around objects with radii as small as 0.6 cm. Low-dark-current perovskite photodetectors can be integrated with an oxide transistor backplane to create a high-resolution optical scanning array capable of imaging flat and curved surfaces.