Various electronic devices have optical sensors that detect the brightness of light. At present, photodiodes that convert differences in light intensity to electric signals are manufactured mainly through high-temperature vapor deposition on a glass substrate of a photoelectric conversion material composed of silicon and other inorganic substances. OPD that Toyobo is developing can be manufactured in a simpler method, in which an organic photoelectric conversion material is dissolved in a solution and then coated on a glass or plastic substrate. This reduces production costs and associated environmental impacts, compared with those of conventional photodiodes. Furthermore, the use of films and other flexible materials as a substrate allows greater freedom in shaping target components, broadening the range of photosensor applications and opening the door to extensive use in various industries.
Toyobo has been developing a diverse range of organic materials by harnessing its sophisticated organic synthesis technologies. Since 2019, Toyobo and CEA have conducted joint research on a power-generating material for organic photovoltaics*3. Moreover, since 2020, Toyobo and CEA have been jointly developing an organic photoelectric conversion material for photosensors, which are indispensable for IoT. This research has culminated in a prototype OPD module with excellent sensitivity capable of detecting weaker light than silicon photodiodes already on the market can detect. Specifically, this prototype attained one of the world's lowest levels of dark current, or below 10-9 A/cm2 when subjected to the voltage of -5V, the benchmark for commercial application. In a joint verification with CEA, Toyobo's photoelectric conversion material was confirmed to have the same level of dark current when coated on either a glass substrate or polyethylene terephthalate (PET) film substrate.
Toyobo is committed to creating a safer society that gives people peace of mind by putting into practical use as soon as possible the material for advanced photosensors which require low dark current used for IoT electrical appliances, fingerprint authentication devices and other product.
*1 According to Toyobo's study as of March 23, 2022.
*2 An electrical current when light is not irradiated. The lower the dark current, the higher the sensitivity of a photosensor.
*3 Refer to Toyobo's news release dated July 31, 2019, https://www.toyobo-global.com/news/2019/release_101.html
Refer to Toyobo's news release dated March 23, 2020, https://www.toyobo-global.com/news/2020/release_117.html