Center for Functional Nanomaterials Seminar

Organic photovoltaic (OPV) devices offer several attractive advantages, such as light weight, low cost, flexibility and capability of high throughput processing, over inorganic solar cells. However, the relatively low power conversion efficiencies of current OPVs limit their general application and commercialization. In order to improve OPV efficiencies, various aspects and parameters need to be considered and optimized, among which development of new organic materials with better sunlight absorption and realization of ordered bulk heterojunction (BHJ) morphologies are considered key factors. We have been focusing on the development of novel methodologies for the synthesis of conjugated polymers with low bandgaps and tunable HOMO/LUMO energy levels. Favorable physical properties including solubility, crystallinity and high charge mobility are general guidelines for the syntheses. In the meantime, it has been well-established that coil-coil block copolymers can phase separate into various ordered morphologies on the nanometer scale, resembling the ideal case of ordered BHJ. We have thus developed a modular approach toward conjugated block and graft copolymers and obtained preliminary results on the phase behavior of these rod-coil copolymers.