Fabrication and optimization of near infrared oganic photodetectors

Organic semiconductors are a promising alternative to inorganic semiconductors for wearable photodetector devices, owing to their flexibility, optical properties and ability to be processed from solutions. Especially, the near infrared region (NIR) between 1000-1700 nm is interesting for applications in medical monitoring, imaging and optical communications, motivating extensive research on organic semiconductors with strong NIR absorption. Here, PPhTQ, a low bandgap donor material with absorption extending into the NIR, was combined with the non-fullerene acceptor IEICO-4F to fabricate and optimize bulk heterojunction organic photodetectors. The results demonstrate that ZnO and MoOx constitute the most effective charge blocking layer combination for this donor-acceptor system. Furthermore, a donor:acceptor ratio of 1:3 was identified as optimal, yielding highest specific detectivity of 3.3 · 109 Jones at 1200 nm. In contrast, increasing the bulk heterojunction thickness was found to negatively impact the detectors responses in the near infrared, with detectivities falling below 109 Jones. Importantly, many devices exhibited measurable photo responses up to 1600 nm, highlighting the potential of PPhTQ based system for NIR photodetection.