In this collaborative project, four scientists at the University of California - Santa Barbara will investigate the design, synthesis and incorporation of new "electroactive polymer surfactant" (EPS) molecules in all-organic polymer photovoltaic materials. The aim of this research is to overcome some of the key stumbling blocks that have plagued other researchers investigating polymer photovoltaic materials, based upon bulk heterojunction systems. The work will be organized around the following three goals: (1) the development of physics-based models and efficient numerical methods for the prediction of phase separation in blends of rod-like polymers with multifunctional copolymer surfactants; (2) the synthesis of new homopolymers and functional block copolymers/oligomers comprising p-type and n-type backbones with a central electronically active moiety, using the design characteristics from (1); and (3) the characterization of the morphology of the blends as a function of composition and process conditions. The Principal Investigators will simultaneously develop a multifaceted educational program in solar energy research, including programs for high-school teachers, workshops for young scientists, and international collaborative experiences for graduate students.
Efficient conversion of solar to electrical energy is likely to be one of the most important means of powering the planet in a sustainable way. Current materials for the conversion of sunlight to electricity are hampered by low efficiency and high cost. Work like that proposed in the present proposal seeks to find new alternatives that circumvent these problems. In particular, organic polymer (plastic) photovoltaic materials show promise as inexpensive alternatives to conventional semiconductor photovoltaic materials. Besides producing new kinds of materials for solar energy conversion, the Principal Investigators of this proposal hope to produce new kinds of scientists with the interdisciplinary expertise needed to make significant contributions to challenging scientific as well as societal problems.
Solar cells convert light from the sun into electricity providing a source of renewable energy. To effectively harness the power of the sun, solar cells with high efficiency need to cover large areas at low cost of production. While most current solar cells are made from silicon, the cost of energy generation is still relatively high compared to combustion of fossil fuels. Solar cells can instead be made from semiconducting polymers that can be synthesized at large scales and made into rugged, mechanically flexible solar cells at potentially low cost using methods from the printing industry. In order to achieve the full potential advantages of polymers we must develop new materials, manufacturing methods, and predictive theories that help us to control their properties. We have designed and synthesized new semiconducting polymers that self-assemble into nanoscale structures. When light strikes these materials, charge is generated at interfaces at the molecular scale. The charge then travels through the polymer to electrodes to provide electricity. We have studied how structures form at the scale of nanometers, features that are 10,000 times smaller than the width of human hair, to improve the ability of these materials to convert light to electricity. These experiments used high intensity x-ray sources to probe these structures as well as analytical methods developed for conventional semiconductors based on silicon. Our research provides new insight into how such structures form and the key role of interfaces in organic solar cells. We have also developed new computational methods to calculate how structures form from polymers deposited from solvents. These methods give us the ability to predict how the critical phase separated structures form during coating processes. The predictive capability gained by development of these methods is important for future manufacturing processes of polymers. The research on this project was carried out by graduate students in a multidisciplinary team. The students gained important training in advanced research methods and in working across intellectual disciplines. The students and their mentors worked to broaden participation in science through outreach activities to K-12 students.
