Enhanced Photomultiplication of Organic Photodetectors via Phosphorescent Material Incorporation

Photomultiplication organic photodetectors (PM-OPDs) were successfully constructed with a planar structure of PBDB-T/ITIC-Br layers as active layer sandwiched by electrodes. Some isolated electron traps PBDB-T/ITIC-Br /PBDB-T near the top surface of PBDB-T will be formed because small content ITIC-Br will permeate into PBDB-T layer prepared by sequential spin-coating method. The PM-OPDs achieve an external quantum efficiency (EQE) of 260% at 360 nm under an applied bias of -9 V. The phosphorescent material FIrpic was incorporated into PBDB-T layer to adjust PBDB-T molecular arrangement for enhancing hole mobility in active layer. The optimal PM-OPDs with PBDB-T:FIrpic (100:10, wt/wt) display an EQE value of 2500% at 360 nm under -9 V applied bias. Linear dynamic range (LDR) of 137 dB and specific detectivity (D*) of 4.2×1012 Jones are also achieved in PM-OPDs with PBDB-T:FIrpic (100:10, wt/wt). Moreover, high-quality imaging with the PM-OPDs as sensing pixel was realized by utilizing imaging system without current preamplifier, indicating that the PM-OPDs has potential application in imaging.