Highly Transparent Organic Photodetectors with Transfer-Printed PEDOT:PSS Top Electrodes
Semitransparent organic photodetectors (ST-OPDs) are constrained by the limited transmittance of conventional electrodes, typically indium tin oxide (ITO) bottom electrodes paired with thin metal top electrodes (e.g., 10 nm Ag), which restrict average visible transmittance (AVT) to below 60%—well short of the ~80% required for electronic displays. This work introduces a cost-effective transfer-printing process for PEDOT:PSS top electrodes, yielding films with >90% transmittance across the ultraviolet-visible-near-infrared spectrum. The resulting ST-OPDs achieve an AVT of 74.8% and a specific detectivity exceeding 5 × 10^11 Jones. The high transparency enables dual-sided responsiveness, demonstrated by photoplethysmography heart-rate monitoring from both device sides, facilitating integration with readout circuits. The transfer-printing method exhibits broad applicability across various active layers. These findings establish a scalable route to high-performance ST-OPDs for integratable, biocompatible, and invisible optical-sensing applications in transparent electronics.