Semi‐Transparent Organic Photodiodes with Near‐Infrared Detection Fabricated by Inkjet Printing

Transparent organic photodetectors are promising for applications in wearable and communication electronics, where they can serve as imperceptible sensors. Yet, common fabrication techniques such as spin coating and evaporation have limited compatibility with high‐throughput production and scalability. In this work, semi‐transparent and opaque organic photodiodes, inkjet‐printed on indium tin oxide electrodes, reaching a transmittance of up to 70.6% in the visible range are demonstrated. The diode's active layer comprises a transparent donor polymer and Y7 as a non‐fullerene acceptor. This bulk heterojunction results in near‐infrared responsivity with maximum values of 12 ± 2 mA W−1 at −2 V and 840 nm for semi‐transparent diodes with Poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate electrodes and 60 ± 7 mA W−1 for opaque devices with Ag electrodes. The diodes exhibit high detection speeds of up to 3 MHz, making them suitable for near‐infrared communication systems for soft robotics as well as wearable health monitoring, as demonstrated by pulse plethysmography.