Dual Interfacial Layer Modulated Tunneling Mode for Low Dark Current Bidirectional Photomultiplication All-Polymer Photodetectors

All-polymer photomultiplication photodetectors have attracted wide interest due to their flexibility and solution processability. However, the high bias required to achieve gain and high dark current density (Jd) continue to constrain their practical applications. In this work, we report low-bias, high-gain photomultiplication all-polymer photodetectors. Specifically, a low donor:acceptor ratio of 1:100 effectively suppresses leakage current and reduces Jd, while still enabling efficient photocurrent gain. By regulating interfacial carrier transport via a dual-hole-blocking layer (d-HBL), the tunneling behavior is effectively modulated, enabling suppressed Jd while maintaining high photomultiplication gain. Devices based on BCP/PFN-Br exhibit Jd as low as 1.74 × 10–6 A cm–2 at −5 V bias. The BCP/PFN-Br device, in particular, achieves an external quantum efficiency (EQE) of 5953% and a measured-noise-based specific detectivity (D*) of 1.95 × 1010 Jones under −5 V bias at a wavelength of 860 nm. While the PFN-Br single-HBL(s-HBL) exhibits higher LDR and D*, the BCP/PFN-Br d-HBL provides stronger Jd suppression and more effective regulation of interfacial carrier tunneling, highlighting a trade-off between the s-HBL and d-HBL configurations. This work demonstrates an effective interfacial strategy for regulating carrier transport in photomultiplication photodetectors, enabling dark-current suppression while maintaining high photomultiplication gain for weak-light sensing applications.