Enhanced photomultiplication in filter-free organic photodetectors for red and NIR light sensing using minimal nonfullerene blends

Abstract

To address the challenges posed by bulky and costly bandpass filters traditionally mounted with the broadband photodetectors for applications like detecting cold metals, this study presents a streamlined approach for developing filter-free bandpass photomultiplication organic photodetectors (PM-OPDs). These devices utilize the charge injection narrowing effect to achieve a selective response to red and near-infrared (NIR) light, with an external quantum efficiency (EQE) significantly exceeding 100%. By using only a minimal amount of the costly NIR-sensitive material Y6 (P3HT : Y6, 100 : 1) and optimizing the thick bulk heterojunction active layer, we enhance electron trapping and promote extensive hole injection, leading to multiplication behavior. These devices demonstrate an impressive EQE of 11 500% at 660 nm and 3080% at 850 nm under a light intensity of 160 nW cm⁻², and a broad linear dynamic range (LDR) of around 100 dB at both wavelengths. Optical absorption simulations confirm the spectrally selective response from 640 to 870 nm, facilitated by the red absorption shoulder of P3HT and NIR absorption by Y6. The potential applications of these filter-free PM-OPDs extend beyond cold metal detection, offering a compact and cost-effective solution for specialized detection needs.