Solution-Processed Self-Powered Panchromatic Organic Photodiode and Its Application in Biomedical Devices

Non-fullerene acceptor (NFA)-based optoelectronic devices have received great research interest because of their unique optoelectronic characteristics like tunable bandgap, strong near-infrared (NIR) light absorption, and enhanced stability. However, the demonstration of a self-powered NIR broadband photodiode with excellent photoresponse and low dark current density comparable to that of commercial inorganic counterpart remains a challenge. Herein, the high-performance solution-processed self-powered organic broadband photodiode is demonstrated by using a narrow bandgap NFA with a low dark current density (J d) of 1.05 nA/cm2 at 0 V. The dark leakage current of the device is greatly improved by adopting a “thick junction” strategy, and the optimized device exhibits a J d of 6.5 nA/cm2 even at a moderate applied bias voltage of −1.5 V. The devices exhibit more than 70% external quantum efficiency in the 550–830 nm wavelength (λ) range and a specific detectivity of 2.65 × 1012 jones at λ ∼ 770 nm under the self-powered mode of operation. The fabricated photodetector is used in photoplethysmography (PPG) measurement, demonstrating its application in real-time heart-rate monitoring and pulse oximetry.