Self-filtering red narrowband photodetector based on a perovskite/organic multi-stack photoactive layer

Abstract

Transmission photoplethysmography (PPG) requires the penetration of biological tissues (such as fingertips) for continuous physiological monitoring, and the red-light band (600-700 nm) is an ideal choice due to its high tissue penetration depth (5-10 mm) and arterial blood absorption characteristics. Existing red-light narrowband photodetectors (NPDs) rely on external optical filters, facing problems such as low quantum efficiency (EQE<10%) and broad bandwidth, which limits their weak light detection capability and sensitivity. In this study, we propose a self-driven red light NPDs without external discrete filter that achieves a narrowband response with a peak at 610 nm and a full width at half maximum (FWHM) of 39.4 nm, thanks to the synergistic effect of light filtering from the perovskite layer and photoresponse from the organic quasi-bilayer structure. The NPD demonstrates a maximum EQE for red light exceeding 30%, along with a low dark current of 1.64×10-8 mA/cm², and a response time less than 26 μs. A transmission-type PPG system integrated with the NPDs successfully captured arterial pulse waves, providing a high signal-to-noise ratio and highly stable red light detection solution for wearable medical devices.