Filter‐Free Narrowband Photomultiplication‐Type Planar Heterojunction Organic Photodetectors

Filter‐free narrowband photomultiplication‐type planar heterojunction (PHJ) organic photodetectors (PM‐PHOPDs) are first realized by employing a thick front donor layer and an ultrathin PC71BM layer. The thick front donor layer is employed as an optical field adjusting (OFA) layer. The sequentially coated PC71BM will diffuse slightly into OFA layer, which works as interfacial electron traps to capture photogenerated electrons for assisting hole tunneling injection. The P3HT/PC71BM‐based PM‐PHOPDs exhibit narrowband response with full‐width of half‐maximum of 32 nm and external quantum efficiency (EQE) of 1700% at 650 nm under −20 V bias. Due to the enhanced hole transport and reduced charge recombination in PHJ compared to those in bulk heterojunction (BHJ), the EQE of P3HT/PC71BM‐based narrowband PM‐PHOPDs is twice as P3HT:PC71BM BHJ‐based narrowband PM‐OPDs under the same bias. The response peak of PM‐PHOPDs is adjusted from 650 to 695 or 745 nm by incorporating SMPV1 or DRCN5T in OFA layers due to the red‐shifted absorption edge. The EQEs of 3600% at 695 nm and 870% at 745 nm are obtained for P3HT:SMPV1 and P3HT:DRCN5T‐based PM‐PHOPDs under −20 V bias, respectively. This work provides a smart strategy to achieve narrowband PM‐OPDs by designing different OFA layers. Filter‐free narrowband photomultiplication‐type planar heterojunction organic photodetectors (PM‐PHOPDs) are first realized by employing a thick front donor layer and an ultrathin PC71BM layer. The narrowband response of PM‐PHOPDs shows tunable peak position from 650 to 695 or 745 nm by varying the donor layer from P3HT to P3HT:SMPV1 (3:1, w/w) or P3HT:DRCN5T (3:1, w/w).