Enhanced Transport in Organic Semiconductors Mediated Through Interfacial Charge Transfer and Cooperative Strong Coupling.

Band structure engineering of organic semiconductors is crucial to achieve the best-performing optoelectronic devices. Strong light-matter coupling is emerging as an unconventional approach to tailoring the band structure through exciton-photon hybridization. This work demonstrates that cooperative strong coupling enhances transport in a bottom-gate, bottom-contact metal-oxide-semiconductor field-effect transistor (MOSFET)-based Fabry-Pérot cavity. Here, the cavity consists of an electrically active layer made of a perylenediimide dye and an inactive, highly absorbing cooperative layer (Rhodamine-B). A large enhancement in electron mobility of the active layer is observed when placed in direct contact with ionic Rhodamine-B. A feeble enhancement is observed in a lossy mirrorless configuration. The cooperative effect still works here, but it is less pronounced due to weak coupling strength. Placing an insulator between the layers prevents charge transfer. Furthermore, replacing the ionic layer with neutral Perylene-Red dye does not affect the electrical properties even when the layers are in direct contact. Here, the improved electrical response is due to interfacial charge transfer and strong coupling that work in tandem. These findings highlight how cooperative strong coupling can serve as an effective strategy for engineering the band structure of organic semiconductors and thereby improving their performance.