Ultraviolet Narrowband Photomultiplication Type Organic Photodetectors with Fabry−Pérot Resonator Architecture

Ultraviolet (UV) narrowband photodetectors play a critical role in missile detection, flame monitoring, optical communication, etc. It is a great challenge to realize UV narrowband organic photodetectors due to wide photo‐harvesting property of organic materials, especially for photomultiplication type organic photodetectors (PM‐OPDs). In this work, a smart strategy is proposed to achieve UV narrowband response by coupling Fabry−Pérot microcavity with PM‐OPDs. PM‐OPDs are realized by using poly(3‐hexylthiophene‐2,5‐diyl):[6,6]‐phenyl‐C71‐butyric acid methyl ester (100:1, w/w) as active layers, exhibiting broadband response range covering from UV–vis region. Series of optical microcavities consisting of Ag/LiF/Ag with UV spectral selectivity are prepared, which are employed to couple with the PM‐OPDs for achieving UV narrowband response. The UV spectral selectivity of optical microcavity can be optimized by tuning the thickness of spacer layer and mirror layers, which can further regulate the photogenerated electron distribution near Al electrode to optimize the external quantum efficiency (EQE) spectra of the PM‐OPDs coupled with optical microcavity. The optimized PM‐OPDs coupled with optical microcavity exhibit EQE of 9300% at 350 nm and narrowband response with 33 nm full‐width at half‐maximum under −15 V bias. This work indicates that PM‐OPDs coupled with optical microcavity should be an efficient strategy for achieving UV narrowband response. Optical microcavities possessing ultraviolet (UV) spectral selectivity are coupled with photomultiplication‐type organic photodetectors (PM‐OPDs) based on poly(3‐hexylthiophene‐2,5‐diyl):[6,6]‐phenyl‐C71‐butyric acid methyl ester (100:1, w/w) as active layers to achieve UV narrowband response. The optimal PM‐OPDs coupled with optical microcavity exhibit 9300% of external quantum efficiency at 350 nm and narrowband response with 33 nm full‐width at half‐maximum under −15 V applied voltage.