Ultra‐Flexible Dual‐Band Organic Photodetectors for Visible and Near‐Infrared Sensing

Abstract Dual‐band organic photodetectors (DB‐OPDs) offer adaptive detection of two distinct wavelengths by switching the voltage, making them promising candidates for wearable bio‐imagers. Although many studies have been conducted on rigid DB‐OPDs to date, flexible DB‐OPD with comparable performance to rigid counterparts has not been reported because of the vulnerability and lower transmittance of flexible substrates and electrodes. In this study, a 5.6‐µm‐thick ultra‐flexible DB‐OPD for visible and near‐infrared (NIR) light selective detection is reported. It shows high mechanical durability with stable electrical characteristics after 500 repetitions of intense bending at a radius of 0.5 mm. Furthermore, high specific detectivities exceeding 10 11 Jones in both the visible and NIR spectral ranges are achieved by incorporating an efficient donor to enhance the photocurrent and depositing a top electron transport layer to suppress the dark current, while minimizing damage to the underlying NIR‐sensitive layer. To validate the feasibility of the ultra‐flexible DB‐OPD in bio‐imaging, dual‐spectral peripheral oxygen saturation (SpO 2 ) measurements are performed under a continuous‐spectrum light source covering both the visible and NIR regions. The results highlight the potential of the ultra‐flexible DB‐OPD for wearable oximeter application.