Optical sensors are omnipresent and CMOS cameras have been used in industry for many years as a simple and inexpensive solution for automated image processing. The Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology (FEP) is now presenting a new generation of organic photodiodes on silicon (OPD-on-silicon).
Conventional, silicon-based CMOS image sensors are technologically limited to a limited wavelength range. They are usually set to the visible part of the light. However, if one would like to detect near-infrared (NIR) light, hybrid solutions such as the combination of indium gallium arsenide and CMOS are usually used. However, the production of such hybrid solutions is significantly more cost-intensive and error-prone than the production in the standard CMOS process.
Here organic photodiodes offer an alternative. The organic layers are easy to integrate at wafer level and therefore cost-effective. At the same time, depending on the material system, they also have a high sensitivity outside the visible wavelength range.
For the first time, the institute presents an array of organic photodiodes with SVGA resolution at the SEMI European Imaging + Sensors Summit 2017. These are 800 × 600 pixels that are available for detection. The exhibit demonstrated that it is fundamentally possible to produce a high-resolution organic photodiode matrix of this size. It is sensitive in the wavelength range up to 1000 nm. With appropriate material adjustments, customer-specific and application-specific organic photodiodes can be developed on this basis and their properties optimized for the specific application.
The issued image sensor was completely manufactured on wafer level and is therefore already close to production. With its extended sensitivity range, it can be used across the full range of conventional industrial, automotive, or medical applications. For example, they could be used in food quality control, as fingerprint sensors or biomedical tests.
The scientists are now making the new technology available to industrial partners in order to jointly develop and produce optimized organic photodiodes and arrays as image sensors for the respective application in practice.