Science News: 2021 Nat. Electron. (IF 33.686), Flexible & Thin Perovskite for Fingerprint Recognition and Document Scanning

　　In November 2021, Nature Electronics (IF 33.686) published the research results of Gerwin H. Gelinck and Eric A. Meulenkamp, respectively from Eindhoven University of Technology in the Netherlands and the Netherlands Applied Science Research Organization. The research team used solution-processed perovskite to develop a flexible thin-film image sensor suitable for fingerprint recognition and document scanning.

　　Since the solution-processed photodetector can be manufactured on a plastic substrate at low cost and its absorption spectrum can also be adjusted by chemical design, it can be used for large-area light sensing applications. However, it is still challenging to manufacture a photodetector with low dark current and integrate it into a high-resolution backplane. In this study, the researchers placed a solution-processed metal halide perovskite photodiode on top of an amorphous indium gallium zinc oxide transistor backplane and used it to create a flexible image sensor. The thickness of this image sensor was about 100 μm and the resolution was 508 pixels per inch. Researchers also developed pixel edge overlays for the system, which could reduce electrode current leakage and dark current density.

　　The front panel and the oxide thin film transistor (TFT) back panel of the solution-processed metal halide perovskite photodetector (PPD) constructed a graphic array (VGA; 640×480 pixels) scanner, which could capture full-color images and high-resolution fingerprints. Through the optimization of the PPD front panel and the use of pixel ECL, low dark current density of 10⁻⁶ mA cm⁻², 66% external quantum efficiency (EQE) and high photodetection rate of 1.3×10¹² Jones have been obtained in the visible spectrum. The research team used photodetector characteristic analyzers for analysis. The research results showed that high photodetection can be achieved in the wavelength range of 550 nm to 770 nm when the low noise current was combined with high external quantum efficiency. The researchers also showed that the imager could be used for document scanning and biometric fingerprint recognition. Furthermore, it could be wrapped around objects with radii as small as 0.6 cm.