Silicon photodiodes have been the cornerstone of photo-detection technologies for decades, but their rigid structure poses many constraints for low-cost, large-area scaling applications. This brings challenges to emerging photo-detection applications. To realize larger-area photodetection and low-cost photodiodes on flexible substrates, we need to look into new materials systems.
Organic photodiodes are often made from polymers, possessing advantages like structural flexibility. By detailed characterization methodology, researchers investigated the sources of low-frequency electronic noise in such diodes, finding that the charge-collecting electrodes play an important role in the low-frequency noise. This lays the foundation for designing low-noise organic photodiodes.
After optimized design, organic photodiodes can reach performance level of commercial silicon photodiodes in most metrics, especially in the visible spectrum. For example, response, sensitivity, linearity, power consumption, etc. Their response time still falls behind silicon diodes, but is already sufficient for most video-rate applications.
The solution-based processing of prototypical organic photodiodes brings many application opportunities for them. For instance, large-area, flexible ring-shaped organic photodiodes can be used to realize biometric monitoring. Such diodes are of low cost and can be fabricated on various non-planar substrates, with performance rivaling commercial silicon devices already. They are promising for emerging photoelectronic technologies.
Fig. 1 Comparison of SiPD and OPD performance.
Fig. 2 Steady-state dark current density and electronic noise characteristics in SiPDs and OPDs.
Fig. 3 Temporal response characteristics in SiPDs and OPDs.
Fig. 4 Flex-OPDs and application in PPG.