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PM6:Y6 is adopted as the active layer to prepare highly efficient organic photodetectors (OPDs), which is applied to realize a biometric sensor for real‐time heart‐rate monitoring. Here, the effects of the device structure, thickness, deposition process, and solvent on the subsequent performance of the OPDs are examined. Through judicious choice of the fabrication conditions, an OPD is obtained displaying a dark current density of less than 8.77 × 10−10 A cm−2, a responsivity of greater than 0.516 A W−1, and a high detectivity of 3.1 × 1013 Jones, measured at bias of −2 V (870 nm). This OPD featured a wide linear dynamic range (LDR, 530 nm) of 104 dB at −2 V, an ultrahigh cutoff frequency (750 kHz) and rise/fall times of less than 220 ns under a reverse bias of −2 V. This sub‐microsecond response and high detectivity is comparable with, and in some cases better than, those of the state‐of‐the‐art perovskite‐PDs and Si‐PDs. The OPD displays consistent responses, good repeatability, and stability [ambient: 50% humidity, 25 °C)]. The air‐stable and portable OPD‐based photoplethysmogram system provides clear signal resolution, potentially benefitting its applicability to blood pressure monitoring.

With the advancement of portable optoelectronics, organic semiconductors have been attracting attention for their use in the sensing of white and near-infrared light. Ideally, an organic photodiode (OPD) should simultaneously display high responsivity and a high response frequency. In this study we used a ternary blend strategy to prepare PM6: BTP-eC9: PCBM–based OPDs with a broad bandwidth (350–950 nm), ultrahigh responsivity, and a high response frequency. We monitored the dark currents of the OPDs prepared at various PC71BM blend ratios and evaluated their blend film morphologies using optical microscopy, atomic force microscopy, and grazing-incidence wide-angle X-ray scattering. Optimization of the morphology and energy level alignment of the blend films resulted in the OPD prepared with a PM6:BTP-eC9:PC71BM ternary blend weight ratio of 1:1.2:0.5 displaying an extremely low dark current (3.27 × 10−9 A cm−2) under reverse bias at −1 V, with an ultrahigh cut-off frequency (610 kHz, at 530 nm), high responsivity (0.59 A W–1, at −1.5 V), and high detectivity (1.10 × 1013 Jones, under a reverse bias of −1 V at 860 nm). Furthermore, the rise and fall times of this OPD were rapid (114 and 110 ns), respectively.

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