Narrowband absorption far-red organic photodetector for photoplethysmography

Narrowband absorption organic semiconductors for spectrally selective photodetection are highly attractive for emerging applications requiring light weight and customizable devices. While narrowband absorption photodetectors have achieved success in the visible range, far-red (650 to 750 nm) narrowband absorption photodetectors remain scarce. This wavelength range is relevant for applications in medical diagnostics, such as photoplethysmography for blood oxygen saturation detection. A non-fullerene bulk heterojunction organic photodetector with narrowband response in the far-red spectrum has been fabricated. The photodetector exhibits a high detectivity of 5.12×10¹² Jones at a bias of -2 V. The photodetector’s full-width at half-maximum of the responsivity peak is 85 nm, the smallest spectral width among solution-processed devices. The response speed is 115.6 kHz. The photodetector responds in the microsecond range. The potential of the photodetector for blood oxygen saturation measurement is demonstrated.