Project R-10243

Design and synthesis of organic semiconductors for near-infrared 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 promises of this innovative concept, dedicated strategic research is required to further optimize the device output and to elucidate its 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, blend nanomorphology studies and basic cavity device analysis, while more in-depth device photophysics will be conducted by collaborators. The final goal is to unravel structure-photodetector relations, providing a leverage for commercialization of NIRphotodetectors.

01 November 2019 - 31 October 2021