High Responsivity of Narrowband Photomultiplication Organic Photodetector via Interfacial Modification

Narrowband-response organic photodetectors with high responsivity are widely demanded in areas of substance detection, industry automation, smart wearable devices, etc. Photomultiplication-type organic photodetectors (PM-OPDs) with high responsivity usually have a broadband photoresponse due to the broadband absorption nature of the photoactive materials. In this work, effort is made to develop a high-performance filterless narrowband PM-OPD using the charge injection narrowing (CIN) effect. A 0.8 nm thick Al₂O₃ interlayer is used to mitigate the dark current density (J_D) in the narrowband PM-OPD, prepared using a 2.8 µm thick blend layer of P3HT:[6,6]-phenyl-C₇₀-butyric acid methyl ester (PC₇₀BM), achieving a peak responsivity of 1334 A W⁻¹ at 650 nm, with a full-width at half-maximum of 40 nm. The narrowband PM-OPD also possesses an impressive high specific detectivity of 9.73 × 10¹³ Jones. It is shown that the use of a 0.8 nm thick Al₂O₃ interlayer significantly suppresses the J_D, creating a high energy barrier at the anode/photoactive interface and achieving a narrowband photoresponse behavior due to the CIN effect. The results of this work provide an exciting option for a variety of applications for OPDs with low cost, flexibility, and high sensitivity.