Collaborative Research: High-performance Crystalline Bulk Heterojunction Organic Solar Cells

~~ Collaborative Research: High-petformance crystalline bufk heterojunction organic solar cells Intellectual Merit: The field of organic electronics seeks to reduce the cost of electronic devices by replacing photolithographically patterned silicon with printed or spray-patterned organic semiconductors. This project will study the nucleation and growth of small-molecule semiconductors, to discern ways to precisely control grain size, surface coverage and donor I acceptor interfaces to yield lowcost, highly efficient solar cells. By using high-performance soluble smallmolecule semiconductors, the creation of appropriate thin-film morphologies will insure excellent charge transport, maximizing the performance of the device. Crystallization and film growth of solution blends of a/l small molecule semiconductors is a nascent area of study, and the typical high electronic performance of high-purity small molecule systems promises significant advances in photovoltaic performance should such performance be realized in small molecule blends. The project will require substantial collaboration between mathematicians for modeling nucleation, crystal growth and phase separation of the blended semiconductors, chemists for the design. synthesis and tuning of appropriate donor and acceptor semiconductors, and engineers for the analysis of films and construction and evaluation of solar cells. The team will work synergistically to understand the mechanisms of grain growth, tailor donor and acceptor to maximize voltage and current, and improve surface treatments and deposition methods to allow the formation of large-area devices. Broader Impact: The understanding of nucleation and growth of high performance soluble small molecule semiconductors will have Significant impact in an array of endeavors across the spectrum of electronic devices. Of course the most critical area of impact will be the energy sector, where efficient solar cells that are light weight and inexpensive will allow economical energy generation even in areas not typically considered suitable for solar power. However, fields such as solid-state lighting (organic light emitting diodes), flexible displays and radio-frequency identification tags (organic tranSistors) will also benefit from the results of this project, because understanding the growth of high performance soluble semiconductors is critical to optimizing these devices as well. The project will require the development of new p-type and n-type organic semiconductors, which should also find use in the fabrication of low-cost complementary electronic circuitry. To maximize the training impact of this research program, the participating research groups at Kentucky and Princeton will exchange researchers to enhance the cross-disciplinary training of participating students. This exchange will, for example, introduce engineering researchers to organic synthesis, and anow mathematics graduate students to learn film growth and device fabrication techniques. We will also run an annual "summer camp", to immerse all participants in a joint review of the project. This exchange of personnel is critical to prodLicing cross-trained scientists to insure a competitive technology workforce. The participating groups will also continue outreach to local primary and secondary schools, mentoring high school students in research projects and participating in outreach activities at elementary and middle schools. TP17014468