Michael Kelley with Volodimyr Duzhko
Spectroscopic Studies of Charge and Energy Transfer Processes in Self-Organizing Heterogeneous Photovoltaic Materials
In response to growing needs for renewable and pollutant-free energy resources, conversion of sunlight into electricity by solar cells is one of the most promising alternatives. Utilization of organic photovoltaic materials allows for improving the cost-effectiveness of the fabrication approaches. However the cost-efficiency of state-of-the-art organic photovoltaic devices needs to be further improved. Self-assembled organic materials, such as liquid crystals, possess efficient electronic and optoelectronic properties due to a high degree of structural order and can be fabricated by inexpensive approaches. In this project, we study the structural, optoelectronic, and charge transfer properties of heterogeneous organic photovoltaic materials produced through the co-assembly of p-type and n-type semiconducting liquid crystals. When these liquid crystals are coaxed to self-assemble into nanostuctured blends, photo-generation of free charges at the p-n interface and their collection at the electrodes can be improved. This research will be concerned with the measurement of the self-assembly and charge transfer in mixtures of 2,3,9,10,16,17,23,24-Octakis(octyloxy)-29H,31H-phthalocyanine and N,N′-bis(1-hexylheptyl)-perylene-3,4:9,10-bis-(dicarboximide) or N,N’-Ditridecylperylene-3,4,9,10-tetracarboxylic diimide through steady-state and transient UV-vis-NIR optical absorption spectroscopy to determine the structure of the energy levels, photoluminescence spectroscopy to determine the charge transfer efficiency, and time-of-flight measurements to determine the charge transportation efficiency. Comparison of the measurements of these materials as solutions, aggregate fibers, and solid films will reveal changes in their properties at different levels of aggregation. This research will help determine the viability of using liquid crystal photovoltaic structures to satisfy the need for renewable energy in the near future.