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

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 (<1.5x10(-10) A cm(-2)) and one order of magnitude lower spectral-noise density (2.1x10(-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.