High-Performance Phototransistor Based on Graphene/Organic Heterostructure for In-Chip Visual Processing and Pulse Monitoring

Mimicking the real-time sensing and processing capabilities of human retina opens up a promising pathway for achieving vision chips with high-efficient image processing. The development of retina-inspired vision chip also requires hardware with high sensitivity, fast image capture, and the ability to sense under various lighting conditions. Herein, a high-performance phototransistor based on graphene/organic heterojunction is demonstrated with a superior responsivity (2.86 x 10(6) A W-1), an outstanding respond speed (rise time/fall time is 20 mu s/8.4 ms), and a remarkable detectivity (1.47 x 10(14) Jones) at 650 nm. The phototransistor combines weak-light detection capability (minimum detectable light intensity down to 2.8 nW cm(-2)) with gate-tunable bi-directional photoresponse capable of simultaneously sensing and processing visual images for light intensities ranging over six orders magnitude (10-10(7)nW cm(-2)). Moreover, the phototransistor also exhibits an intriguing feature undiscovered in other retina-inspired devices, namely that it can real-time monitor the human pulse signal and heart rate by using photoplethysmography technology, and the measured heart rate error is only 0.87% compared with a commercially available sensor. This work paves the way for the development of low-light and bio-signal sensitive artificial retinas in the future.