Project R-9067

Design and synthesis of organic semiconductors for nearinfrared photodetection with bulk heterojunction organic cavity devices (Research)

Blending organic electron donors and acceptors yields intermolecular charge transfer (CT) states with additional optical transitions below their optical gaps. In organic photovoltaics, such CT states play a crucial role and they limit the operating voltage. Due to its extremely weak nature, direct intermolecular CT absorption often remains undetected and unused for photocurrent generation. However, the negligible external quantum efficiency in the spectral region of CT absorption can substantially be increased through the use of optical cavities, allowing narrow-band detection with substantial quantum efficiencies and resonance wavelengths extending into the nearinfrared (NIR). The broad spectral tunability via simple variation of the cavity thickness makes this novel, flexible and potentially visibly transparent device principle highly suitable for integrated low cost (spectroscopic) NIR photodetection. Despite the high promises of this innovative concept, dedicated frontier research is required to further optimize the device output and to elucidate its fundamental limitations. In my PhD project, the emphasis will be on the development of high-quality (high-HOMO) electron donor and (low-LUMO) electron acceptor materials and their (basic) cavity device analysis, while more in-depth device, photophysics and blend nanomorphology studies will be conducted in collaboration with partner groups, with the final goal to unravel structure-solution processing-photodetector relations.

01 October 2018 - 30 September 2022