Interfacial Engineering for Photomultiplication Type Organic Photodetectors with Signal-Noise-Ratio Over 89 000

Photomultiplication type organic photodetectors (PM-OPDs) exhibit obvious superiority in weak light detection due to their low dark current density (JD) and large photo-induced current density (JPI). The JD is one of the important parameters that influences light detection sensitivity of PM-OPDs, how to effectively suppress the JD is a great challenge to improve the performance of PM-OPDs. In this work, the JD of PM-OPDs can be suppressed by employing PTAA or doped-PTAA as the interfacial layer replacing PEDOT:PSS layer. The PM-OPDs with PTAA layer exhibit a low JD of 2.3 x 10-7 A cm-2 under -6 V bias, which is much smaller than 1.4 x 10-6 A cm-2 for PM-OPDs with PEDOT:PSS layer. The small molecule DRCN5T is incorporated into PTAA to further passivate surficial defects of PTAA films, which is conducive to reducing the leakage current of PM-OPDs. The optimal PM-OPDs exhibit rather low JD of 8.4 x 10-8 A cm-2 under -6 V bias, as well as external quantum efficiency (EQE) of 31700% and specific detectivity (D*) of 1.2 x 1013 Jones at 370 nm. The signal-noise-ratio of optimal PM-OPDs arrives to 89600 under -4.5 V bias under white light illumination with intensity of 1.5 mW cm-2. The dark current density (JD) as one important parameter determines the light detection sensitivity of PM-OPDs, which can be suppressed by employing interfacial engineering. The optimal PM-OPDs exhibit a rather low JD of 8.4 x 10-8 A cm-2 under -6 V bias. The maximum EQE value of 31700% is achieved in PM-OPDs under -6 V bias, accompanied with large signal-noise-ratio of 89600. image