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 (J_D) and large photo-induced current density (J_PI). The J_D is one of the important parameters that influences light detection sensitivity of PM-OPDs, how to effectively suppress the J_D is a great challenge to improve the performance of PM-OPDs. In this work, the J_D 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 J_D of 2.3 × 10⁻⁷ A cm⁻² under −6 V bias, which is much smaller than 1.4 × 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 J_D of 8.4 × 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 × 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.