Highly sensitive photomultiplication type polymer photodetectors by manipulating interfacial trapped electron density

Abstract

Photomultiplication type polymer photodetectors (PM-PPDs) are successfully achieved via interfacial trap-assisted hole tunneling injection from external circuit. The external quantum efficiency (EQE) of PM-PPDs is mainly determined by the number of injected holes from external circuit and flowing across the devices. Although the trapped electron density near Al electrode can be increased for efficient hole tunneling injection by decreasing the thickness of active layers, which also makes the PM-PPDs vulnerable to breakdown. A smart strategy is firstly proposed to obtain large EQE values by decreasing the thickness of active layers and keep excellent withstanding large bias characteristic of PM-PPDs by using wide bandgap polymer poly-TPD as buffer layer. The optimal double layered ternary PM-PPDs were obtained with 40 nm poly-TPD as buffer layer and 90 nm P3HT:PBDB-T:PC61BM (80:20:2, wt/wt/wt) as active layers, exhibiting a rather large EQE value of 21400% and specific detectivity of 1.0 × 1013 Jones at 430 nm under −8 V bias. This work indicates that inserting wide bandgap and high hole mobility material as buffer layer should be an efficient strategy to prepare highly sensitive PM-PPDs, benefiting from the increased hole tunneling injection from external circuit and efficient hole flowing across the devices.