Charge-Integrating Organic Heterojunction Phototransistors for Wide Dynamic Range Image Sensors
The performance of solution-processed photo-transistors is substantially advancing, exhibiting larger photoconductive gain with a sublinear responsivity to irradiance. These characteristics enable A logarithmic Sensing of Irradiance, which is akin to the human eye and has a wider dynamic range than photodiode-based image sensors. Here we present a novel solution-processed phototransistor comprised of a heterostructure between a high mobility organic semiconductor and an organic bulk heterojunction. The device efficiently integrates photo-generated charge then quickly discharges it, which significantly increases signal-to-noise ratio at video frame rates. Phototransistor-based image sensors processed without photolithography on plastic integrate charge with external quantum efficiencies above 100% at 100 frames per second (fps). In addition, the sublinear responsivity to irradiance of these devices enables a wide dynamic range of 103 dB at,30 fps, which is competitive with state of the art image sensors.