Low-Cost Copper Electrode for High-Performance Panchromatic Multiplication-Type Organic Photodetectors with Optical Microcavity Effect

作者：Yang, Liqing; Guo, Dechao; Li, Ji; He, Guo; Yang, Dezhi; Vadim, Agafonov; Ma, Dongge^*

来源：Advanced Functional Materials, 2022, 32(20): 2108839.

DOI：10.1002/adfm.202108839

• copper electrodes
• flexible
• organic photodetectors
• panchromatic
• photo-multiplication

Low-cost and flexible panchromatic organic photodetectors (OPDs) are one of the most promising alternatives in next-generation wearable electronics, but they still face the formidable challenges of replacing brittle indium tin oxide electrode and suffer from low near-infrared (NIR) photo-response. Herein, the low-cost metal copper (Cu) is used as a semi-transparent anode to fabricate high-performance panchromatic multiplication-type OPDs. Because of the advantages of smooth surface, lower sheet resistance, and good transmittance, high-quality optical resonant cavity forming between Cu anode and aluminum cathode greatly enhanced the weak sub-bandgap response of intermolecular charge transfer states in NIR region, while also retaining a good response in the UV-vis region. Due to the good hole-collecting ability, the Cu electrode is suitable for realizing the photo-multiplication effect. Accordingly, the resulting OPDs achieve a panchromatic response ranging from the UV (300 nm) to NIR (900 nm) region. The maximum external quantum efficiency (EQE) reaches 117 040% at 350 nm, and the relatively high EQE of 25 468% is realized even at 765 nm. Furthermore, a flexible OPD is successfully fabricated by using polyethylene terephthalate substrate with Cu anode to achieve the real-time detection of human blood oxygen pulse signals.