Strong light-matter interaction in highly ordered organic semiconductor thin films

Organic semiconductors are important optoelectronic materials that enabled high quality display applications and are rapidly entering new areas of applications such as photodetectors and flexible solar foils due to their inherent mechanical flexibility and promising optoelectronic properties. Despite these exciting developments, the charge carrier mobility in organic semiconductors is orders of magnitude lower than their inorganic counterparts limiting their device performance in terms of switching speed and power efficiency. While recent work on highly ordered organic semiconductor thin films show long-range order is effective in boost charge transport and operation speed of organic electronic devices, the carrier mobility achievable is still at least one order of magnitude lower than crystalline inorganic semiconductors. Exciton-polariton, quasiparticle formed by strong coupling of exciton and photons has been identified as one way to enhance charge transport in organic semiconductors by theoretical studies. However, there is a mixture of experimental results reported, some observed polariton enhanced charge transport while others didn’t. Since there isn’t a well-established protocol for the experiment, different groups use different cavity structures, and most studies probe the charge transport by a transistor structure often under dark conditions where the polaritons are not generated. In this proposal, we aim to characterize the charge of transport of highly ordered organic semiconductors under strong coupling regime using a set of state-of-the-art charge transport measurements to convincingly unveil the effect of polariton on charge transport of organic semiconductors. We will further investigate the conditions required to maximize the effect of polariton enhanced charge transport.
Finally, a proof-of-concept photodetector device based on highly ordered organic semiconductor films under strong coupling will be prepared aiming to advance the organic electronic device performance to unprecedented level by combining the excellent transport of organic thin film crystals and the polariton-enhanced transport.