Opto-Electronic Device Signatures and Sensing with Organic Molecule Exciton States

Many new molecular materials being developed to increase efficiency in organic light emitting diodes and photovoltaics (OLEDs and OPV) rely on exciton interconversion between singlet and triplet states. These high binding energy excitons, with tunable spin character, are also under investigation for applications in quantum information science and spin- based computation. While detailed information about interconversion processes is accessible to ultra-fast optical measurements, within opto-electronic (OE) devices a multitude of processes can overwhelm reliable signal related to exciton dynamics. Certain signature measurements, such has half bandgap turn on in OLEDs as an indicator of triplet fusion, have proved to be unreliable indicators of interconversion processes. In our projects, we work to connect the photophysics to OE device physics to uncover the relationship between exciton dynamics and device output. We demonstrate measurements and modelling of the spin dependent singlet fission process in magnetic field-dependent OE device measurements and corresponding ultra-fast photophysical measurements that show simple EO devices can be used to estimate the zero field splitting spin parameters and sense magnetic fields using exciton states in molecules. Recent results that connect the impact of varying the molecular packing on singlet fission dynamics and related changes to OE device output will be shown.