Polariton formation in functionalized tetracene for manipulating excited states dynamics and photochemistry

Understanding singlet fission, a charge carrier multiplication process, and how the singlet fission and the competing processes can be manipulated with external parameters within the same material system is of considerable interest for enhancing optoelectronic device performance. Exciton polaritons, formed by strong exciton-photon coupling in organic films in microcavities, have been shown to manipulate the energy landscape that may be used to control the photophysics and photochemistry in existing singlet fission materials. To efficiently utilize exciton polariton formation to enhance singlet fission and suppress competing processes such as relaxation into low-energy trap states, it is necessary to establish how the properties of polaritons in singlet fission materials depend on molecular photophysics and microcavity configurations. We present a systematic study of strong coupling in functionalized tetracene (R-Tc), and how it affects its photophysics and photochemistry, depending on film morphology, placement in the cavity (to achieve various degrees of overlap with the cavity electric field), and cavity design. We probe cavity-coupled and uncoupled molecular populations and examine the effects of intermolecular interactions on the excited state dynamics and polariton formation and properties. By varying magnetic field, we create different excited states relaxation scenarios and determine how the polariton states participate in the competition between the singlet fission and relaxation into trap states. We observe magnetic field-enhanced emission from exciton and polariton states and cavity-suppressed emission from low-energy trap states. We also report on effects of polariton formation on photodimerization of R-Tc and discuss how concurrent studies of photochemistry and photophysics promote understanding of singlet fission and polariton formation through the evolution of excited states during photodegradation.