Researchers discovered that trap states govern the performance of organic photodetectors, limiting their detectability. Organic photodetectors (OPDs) have enormous potential for low-cost imaging, health monitoring, and near-infrared sensing applications. However, before these applications can be commercialized, the performance of these devices must be improved.
Recent research on organic photodetectors based on donor-acceptor systems has yielded narrow-band, flexible, and biocompatible devices, the best of which achieve external photovoltaic quantum efficiencies close to 100%. However, the high noise produced by these devices in the off-state limits their specific detectivity, severely reducing performance when measuring faint light, for example.
They discovered that the high noise in the off state is caused by unwanted trap states distributed near the organic semiconductor’s mid-gap. The physicists discovered a direct correlation between the characteristics of trap states and the off-state of OPDs by measuring the number of traps.
We reveal the interplay between traps and charge-transfer states as a source of dark current by modeling the dark current of several donor-acceptor systems and show that traps dominate the generation processes, thus being the main limiting factor of OPD detectivity.
The newly discovered relationship clarifies the operation of OPDs and provides direction for future research in the field. The findings may refocus attention on the cause of OPDs’ poor performance, which was previously unknown.
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