Dark Current in Broadband Perovskite-Organic Heterojunction Photodetectors Controlled by Interfacial Energy Band Offset.

Lead halide perovskite and organic semiconductors are promising classes of materials for photodetector (PD) applications. State-of-the-art perovskite PDs have performance metrics exceeding silicon PDs in the visible. While organic semiconductors offer bandgap tunability due to their chemical design with detection extended into the near-infrared (NIR), perovskites are limited to the visible band and the first fraction of the NIR spectrum. In this work, perovskite-organic heterojunction (POH) PDs with absorption up to 950 nm are designed by the dual contribution of perovskite and the donor:acceptor bulk-heterojunction (BHJ), without any intermediate layer. The effect of the energetics of the donor materials is systematically studied on the dark current (J d ) of the device by using the PBDB-T polymer family. Combining the experimental results with drift-diffusion simulations, it is shown that J d in POH devices is limited by thermal generation via deep trap states in the BHJ. Thus, the best performance is obtained for the PM7-based POH, which delivers an ultra-low noise current of 2 × 10 -14  A Hz -1/2 and high specific detectivity of 4.7 × 10 12  Jones in the NIR. Last, the application of the PM7-based POH devices as NIR pulse oximeter with high-accuracy heartbeat monitoring at long-distance of 2 meters is demonstrated.