Efficient Near-Infrared Organic Photodetectors with Spectral Response up to 1600 nm for Accurate Alcohol Concentration Detection.

The development of near-infrared organic photodetectors (NIR-OPDs) in 1000-1700 nm is essential for medical monitoring, food quality inspection, machine vision, and biomedical imaging. However, when solving the high dark current density ( J D ) in bulk-heterojunction (BHJ) NIR-OPDs based on narrow-bandgap systems, it is often accompanied by photocurrent loss, which is a great challenge in achieving high-performance NIR-OPDs. Here, an ideal hybrid pseudo-PHJ (planar-heterojunction)/BHJ structure is proposed to overcome this challenge, which is introducing the N2200 layer between the cathode and BHJ. The introduction of the N2200 raises the external charge injection barrier and reduces the trap density, thus achieving significant suppression of J D (6.22 × 10 -7 A cm -2 at -0.2 V bias, about 2 orders of magnitude lower compared to the BHJ NIR-OPDs). Meanwhile, the hybrid structure combines the advantages of PHJ and BHJ, thus maintaining a high photocurrent, resulting in responsivity and detectivity of 18.71 mA W -1 and 4.19 × 10 10 Jones, respectively, at 1400 nm at -0.2 V bias, which is superior to the performance of BHJ NIR-OPDs. And the hybrid structured NIR-OPDs are proven to rapidly quantify the alcohol content of mixtures to within 2% accuracy, which exhibits great potential for application in the food and pharmaceutical industries.