Dilution‐Induced Self‐Assembly PEDOT:PSS Interlayer Enables Low‐Noise Near‐Infrared Organic Photodetectors for High‐Contrast Imaging

Abstract Poly(3,4‐ethylenedioxythiphene):poly(styrene sulfonate) (PEDOT:PSS) is widely used as hole transport layer in photodiodes due to its deep work function, flexibility, low cost, and commercialization potentials. However, organic photodetectors (OPDs) using commercial PEDOT:PSS (C‐PEDOT:PSS) interlayers usually suffer from high noise currents. Here, a simple dilution‐induced strategy is proposed for constructing an ultrathin self‐assembled PEDOD:PSS layer (D‐PEDOT:PSS). Dilution‐induced chain disentanglement leads to smaller grain sizes, which is beneficial to reduce defects and enhances selective charge transport. This enables the fabrication of near‐infrared PM6:Y6 organic photodetectors with three orders of magnitude lower ultra‐low dark current (<1.5×10 −10 A cm −2 ) and one order of magnitude lower spectral‐noise density (2.1×10 −14 A Hz −1/2 ) compared to devices using untreated PEDOT:PSS, at ‐0.1 V applied bias. With low dark current and enhanced responsivity, the shot‐noise‐limited detectivity increases by 35 times. An imaging system using OPDs as a sensing pixel has achieved high‐contrast images, demonstrating the imaging potential of the OPDs. The universality of this strategy to enhance the performance of OPDs is further demonstrated through three additional donor‐acceptor blends. This study presents a simple and effective strategy to reduce the noise current of PEDOT:PSS‐based OPDs and provides insights into the correlation between interfacial properties and the performance of OPDs.