High Responsivity of Narrowband Photomultiplication Organic Photodetector via Interfacial Modification

Abstract 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.