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

Abstract 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.