Dutch scientists have developed a new metal halide perovskite scanner for identifying fake documents or synthesized fingerprints with greater accuracy and precision.
Metal halide perovskites are renowned for their high light absorption coefficient, high charge mobility and strong photoluminescence. This makes them a strong and promising candidate for fabricating next-gen solar cells.
But while engineers have primarily used these materials to create solar cells or other solar technologies, they can also substitute silicon or other semiconductors in light-sensing and optical devices such as photodetectors.
Scientists from the Dutch Organization for Applied Scientific Research and Eindhoven University of Technology, have now shown how 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.
According to the team led by Albert J. J. M. van Breemen, the photodetector follows a so-called inverted stack design, with a molybdenum-chrome alloy (MoCr) as the bottom electrode, coated with a thin HTL layer of PTAA.
A [6,6]-phenyl C61 butyric acid methyl ester (PC61BM)–SnOx layer was placed on top of the perovskite active film, acting as an electron transport layer (ETL).
The scientists also introduced a 50-nm-thick silicon nitride (SiN) edge cover layer (ECL) between the MoCr bottom electrode and the PTAA, which reduced electrode current leakage and consequently dark current density.
Finally, they placed a 100-nm-thick transparent indium tin oxide (ITO) electrode on top of the stack and a transparent thin-film encapsulation barrier.
By integrating their photodetector with a thin-film transistor array, van Breemen and his colleagues have managed to create an ‘all in one scanner.’
According to the scientists, this scanner can be used to collect high quality images of both fingerprints and documents, with a resolution of 508PPI.
As far as its applicability is concerned, the new device could help prevent spoofing attacks on biometric sensors, whereby attackers gain access to sensitive user information on their personal devices.
It can also be used to capture high-resolution images of fingerprints and other important documents, thereby helping identify fake documents or synthesized fingerprints with greater accuracy and precision.
Image and content: Breemen et al/Ingrid Fadelli-Tech Xplore