Adopting Buffer Layer for Improving Signal-to-Noise Ratio of Broadband Photomultiplication Type Organic Photodetectors

The photomultiplication type organic photodetectors (PM-OPDs) are prepared with structure of ITO/PNDIT-F3N/F8BT/Y6-1O:P3HT (100:3, wt/wt)/Al, containing hole traps formed with P3HT surrounded by Y6-1O in active layers. The PM-OPDs exhibit external quantum efficiency (EQE)>100% in the spectral response range from 310 to 910 nm, resulting from electron tunneling injection assisted by trapped hole near ITO electrode. The incorporation of F8BT buffer layers can induce the markedly decreased dark current density (J(D)) due to the large electron injection barrier. The light current density (J(L)) of PM-OPDs exhibits slightly decreased by inserting F8BT buffer layers due to the enhanced electron tunneling injection assisted by the more trapped holes near ITO electrode. The signal-to-noise ratio (SNR) of PM-OPDs achieves over 40-fold increment by inserting appropriate thickness of F8BT buffer layers, resulting from the markedly decreased J(D) and reasonably high J(L). The optimal PM-OPDs exhibit excellent photodetection capability with EQE of 4200% at 360 nm and 6600% at 850 nm, associated with the specific detectivity of 3.9 x 10(11) Jones at 360 nm and 9.7 x 10(11) Jones at 850 nm.