The sun represents the most abundant potential source of pollution-free energy on earth. Solar cells for conversion of light to electricity based on electrically conductive organic polymers offer a simple and potentially low-cost route for renewable electricity production. However, recent increases in the performance of organic photovoltaic (OPV) devices have only been enabled by increasing the complexity of device design and fabrication, which often involves multiple layers. Polymer mixtures have the potential to balance the need for the increase solar energy conversion efficiency with the desire to maintain simplicity and ultimately low cost in device manufacture. The goal of this project is develop OPV devices based on mixtures of three organic polymers, or ternary polymer blends. A series of novel organic polymers with electronic properties desirable for OPV devices will be synthesized to serve as components for these ternary blends. Ternary polymer blends are made into a single thin film using printing techniques. Devices made from these thin films will then be characterized to develop a fundamental understanding of how the ternary blend affects photovoltaic performance. Synergistic interactions within these three-component systems may provide unique enhancements in device performance while maintaining the simplicity of a device made from a single organic polymer layer. The project includes cooperative teaching and research activities between California Lutheran University and the University of Southern California, which feature the joint development of a course to educate non-science undergraduate majors on the importance of energy in a changing world, and plans for involving undergraduates in the research during the summer. International collaborations through the Danish Technical University will provide graduate student exchange opportunities focusing on large area, flexible polymer solar cells.
This goal of this project is to develop a fundamental understanding of ternary blend organic polymer photovoltaics (OPV). Ternary blend OPV combines the practical simplicity of single-layer devices with the performance potential of tandem devices. Specifically, ternary blends based on a fullerene acceptor and two miscible conjugated polymer donors with complementary electronic properties are hypothesized to provide enhanced solar energy conversion efficiency relative to a single polymer. A series of novel organic polymers with electronic and thermodynamic properties desirable for OPV device performance and ease of fabrication will be synthesized to serve as components for these ternary blends. Specifically, modular synthesis will be used to generate pairs of polymers with regularly varying electronic and physical interactions. Polymer blend miscibility will be tuned via polymer surface energy, and polymer-polymer mixing will be used to determine the limits of this design principle. OPV devices will be fabricated using printing techniques to make thin films of ternary polymer blends. Through this approach, the research will gain fundamental understanding of the influence of physical and the electronic relationships between components on the performance and behavior of ternary blend solar cells, and establish design principles for optimal conjugated polymer components in ternary blend solar cells that ensure cooperative electronic function. The project includes cooperative teaching and research activities between California Lutheran University and the University of Southern California, which feature the joint development of a course to educate non-science undergraduate majors on the importance of energy in a changing world, and plans for involving undergraduates in the research. International collaborations through the Danish Technical University will provide graduate student exchange opportunities focusing on large area, flexible polymer solar cells.
