measure light intensity using photodiode equation

In comparison to detectors operating at visible wavelengths, infrared detection poses a significant challenge resulting from the increased thermal generation of dark current because of the reduced semiconductor bandgap. In particular, there is significant interest in developing thin-film devices that extend photodetection to the near-infrared (NIR, wavelength λ = 0.7–1 μm) and shortwave infrared (SWIR, λ = 1–3 μm), since conventional devices based on crystalline III–V semiconductors require complex and costly fabrication processes 6. New photodetectors based on flexible thin films are pushing the boundaries of sensitivity, mechanical flexibility, spatial resolution, and low-cost scalability 1, 2, 3, 4, 5. The model provides theoretical targets for the maximum detectivity that can be obtained at different detection wavelengths in inherently disordered infrared photodiodes. Taking disorder into account, we developed a general physical model to explain the dependence of thermal noise on the effective bandgap and bandtail spread. The low noise in NFA blends was attributed to a sharp drop off in the distribution of bandtail states, as revealed by variable-temperature density-of-states measurements. A significant reduction of the noise and higher detectivity were found in devices using non-fullerene acceptors (NFAs) in comparison to those using fullerene derivatives. This report presents experimental and modeling studies on the noise current in exemplar organic bulk heterojunction photodiodes, with 10 donor–acceptor combinations spanning wavelength between 8 nm. However, for non-crystalline semiconductors, an essential framework is missing to understand and predict the effects of disorder on the dark current. To achieve high detectivity in infrared detectors, it is critical to reduce the device noise.

Measure light intensity using photodiode equation