Enhanced specific detectivity of ternary near-infrared organic photodetectors with a ZnO/PDIN double-electron transport layer for health monitoring†

Near-infrared (NIR) organic photodetectors (OPDs) play a crucial role in various technological applications owing to their outstanding responsivity in the NIR range. The OPD fabricated in this study by incorporating an appropriate amount of the third component into the active layer blend film and applying a zinc oxide/N,N′-bis[3-(dimethylamino)propyl]perylene-3,4,9,10-tetracarboxylic diimide (ZnO/PDIN) double electron transport layer (double-ETL) demonstrated optimal interfacial performance, which effectively minimized energy disorder in the active layer, reducing the carrier recombination loss and enabling a relatively fast charge transfer time. Utilizing the optimal device structure, the dark current (J_D) was decreased to 1.4 × 10⁻¹⁰ A cm⁻² at a bias of −0.1 V, the noise current (i_n) was suppressed to 1.86 × 10⁻¹⁴ A Hz^−1/2 and the specific detectivity (D*) obtained from i_n reached 1.3 × 10¹³ Jones at 808 nm and remained above 10¹³ Jones from 500 to 900 nm. Additionally, the device exhibited a fast response speed of approximately 1.993 μs and a high cutoff frequency of −3 dB exceeding 1 MHz. The NIR-OPD showed perfect device performance in weak optical signal detection and was successfully applied for accurate heart rate and blood oxygen monitoring.