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There are currently various near-infrared (NIR) light sources for sensing applications. To expand the application of NIR sensing, we are advancing research and development a self-emissive NIR-OLED microdisplay featuring a compact form factor and active drive as a new sensing light source.
In general, in the NIR region having a narrow energy gap, an exciton of organic emitters readily decays non-radiatively to the ground state. Therefore, it is challenging to obtain high-efficiency light emission. To overcome this problem, a TADF (thermally-activated delayed fluorescence) material having a rigid electron-accepting unit exhibiting strong electron-withdrawing properties is used as an assisting dopant for a molecule exhibiting fluorescence in the 900nm band. It thereby realized a near-infrared light-emitting characteristic with a longer wavelength, higher efficiency, and higher durability than a conventional device.
Furthermore, in order to actively drive this highly efficient NIR-OLED material on a silicon substrate, a top emission structure is required. To cope with this issue, the optical design was optimized for NIR band emission by the micro-cavity effect. The optimum structure for high-efficiency NIR emission was adopted by examining the structure around the emission layer and the encapsulation process.
By integrating this high-efficiency NIR-OLED device with a CMOS-based high-definition backplane formed on a silicon substrate, it’ll have the potential to be realized a high-efficiency NIR-OLED microdisplay with a pixel pitch of 7.8 μm and a maximum external quantum efficiency of approximately 1% and an emission wavelength of over 900 nm. Through this study, it was confirmed that the NIR light emission was possible with high efficiency with fine pixel in principle. It’s expected to contribute to power saving and miniaturization as a new sensing light source to be applicable to new value creation.
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