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Designing Exciton Polariton Properties in Organic Semiconductor Microcavites

Designing Exciton Polariton Properties in Organic Semiconductor Microcavites

Tuesday, December 6, 2022 at 12:00 pm
Weniger 328

Roshell Lamug

Organic materials are a growing area of research in the development of low-cost sustainable (opto)electronics.One of the areas that has experienced recent dramatic growth is research into strong coupling between organic molecules and resonant structures, such as microcavities. The strong coupling of a semiconductor exciton and a confined cavity photon resulting in light-matter hybrid polariton states has shown the ability to control prop-erties of devices to improve their performance. Understanding strong coupling, and the properties of resultinglight-matter hybrid polariton states, is important for designing the next-generation organic (opto)electronic andphotonic devices. This work presents research on exciton-polariton properties in benchmark organic semiconductors placed in different microcavity structures to study the dependence of strong coupling on (1) reflectivity stopbands of the microcavity, (2) placement of the organic film in the cavity to achieve different overlap withthe cavity electric field, and (3) thickness of the organic film. First, the fabrication process of highly reflecting distributed Bragg reflectors (DBRs) is developed which utilizes sputtered alternating layers of SiO2 and TiO2.Then hybrid cavities composed of a DBR bottom mirror and top metal mirror are used to study the photo-physics and photodimerization of functionalized anthradithiophene (diF TES-ADT)-based films depending on DBR reflectivity characteristics. Finally, strong coupling in functionalized tetracene (TIPS-Tc) films is investi-gated depending on film thickness and placement in a microcavity using multilayer cavities. We observe in thehybrid diF TES-ADT cavities that the cavity photon preferentially couples to disordered molecular populationsin mixed-phase concentrated films. Hybrid cavities also show cavity-dependent photodimerization dynamics thatis correlated with the presence of longer lived emissive states. In multilayer TIPS-Tc cavities, the interaction strength scaling with the square root of the number of absorbers and the electric field is confirmed. Preliminary data shows that the fractions of uncoupled and cavity-coupled populations can be controlled by the thicknessof the active layer in the cavity. This observation will be studied further to investigate how molecular populations uncoupled to the cavity interact with polaritons, and how these interactions can be modified to enhance (opto)electronic device performances.

Oksana Ostroverkhova