Self-Powered Organic Photodetectors with High Detectivity for Near Infrared Light Detection Enabled by Dark Current Reduction

Organic photodetectors (OPDs) for near infrared (NIR) light detection represents cutting-edge technology for optical communication, environmental monitoring, biomedical imaging, and sensing. Herein, a series of self-powered OPDs with high detectivity are constructed by the sequential deposition (SD) method. The dark currents (J_d) of SD devices are effectively reduced in comparison to blend casting (BC) ones due to the vertical phase segregation structure. Impressively, the J_d values of SD devices based on D18 and Y6 system is reduced to be 2.1 × 10⁻¹¹ A cm⁻² at 0 V, which is two orders of magnitude lower than those of the BC devices. The D* value of the SD device is superior to that of BC device under different bias voltages (0, −0.5, −1.0, and −2.0 V) due to the reduction of dark current, which originates from the fine vertical phase separation structure of the SD device. The mechanism studies shows that the vertical phase segregation structure can effectively suppress the unfavorable charge injection, thus reducing the dark current. Also, the surface energy is proven to play a key role in the photocurrent stability. In addition, the flexible OPDs demonstrate excellent performance in photoplethysmography test.