Ultraviolet to near-infrared broadband organic photodetectors with photomultiplication

Abstract

The broadband organic photodetectors (OPDs) with photomultiplication (PM) phenomenon are fabricated by using Y6 doped with rather less PBDB-T as active layers having electron-only transport characteristic. The PM-OPDs with PBDB-T:Y6 (3:100, wt/wt) as active layers exhibit the external quantum efficiency (EQE) of 18,000% at 350 nm and 15,000% at 870 nm under 1 V bias. The PM-OPDs exhibits a broad spectral response range from 320 to 950 nm, which is mainly determined by the trapped hole distribution near Al electrode. The working mechanism of PM-OPDs should be attributed to interfacial trap-assisted electron tunneling injection, which can be further confirmed from the EQE spectral shape of PM-OPDs with different active layer thickness. The n-type polymer PZ1 was selected as interfacial layer to be inserted between PEDOT:PSS and active layers, which makes PM-OPDs with PZ1 interfacial layer work well under forward and reverse bias. This work may provide a smart strategy to achieve broadband PM-OPDs by adjusting the distribution of trapped charge near electrode.