Organic and hybrid (organic/inorganic) solar cells are an attractive alternative to traditional silicon-based photovoltaics due to low-temperature, solution-based processing and the potential for rapid, easily scalable manufacturing. Using oxide semiconductors, instead of fullerenes, as the electron acceptor and transporter in hybrid solar cells has the added advantages of better environmental stability, higher electron mobility, and the ability to engineer interfacial band offsets and hence the photovoltage. Further improvements to this structure can be made by using metal oxide nanostructures to increase heterojunction areas, similar to bulk heterojunction organic photovoltaics. However, compared to all-organic solar cells, these hybrid devices produce far lower photocurrent, making improvement of the photocurrent the highest priority. This points to a less than optimized polymer/metal oxide interface for carrier separation. In this article, we summarize recent work on examining the polymer structure, electron transfer, and recombination at the polythiophene-ZnO interface in hybrid solar cells. Additionally, the impact of chemical modification at the donor-acceptor interface on the device characteristics is reviewed.
Julia W.P. Hsu can be reached at Sandia National Laboratories, Albuquerque, NM 87185–1415, USA; tel. 505–284–1173; and e-mail firstname.lastname@example.org. After July 2010, she can be reached at UT Dallas; e-mail email@example.com.
Currently, Hsu is a principal member of the technical staff at Sandia National Laboratories. In August 2010, she will move to the University of Texas at Dallas as a Texas Instruments Distinguished Chair in Nanoelectronics. She received her undergraduate degree from Princeton University and her master's and PhD degrees from Stanford University. After two years as a postdoctoral researcher at Bell Labs, Hsu joined the faculty at the University of Virginia as an assistant professor of physics, earning tenure there in 1997. In 1999, she returned to Bell Labs as a member of the technical staff. In 2003, she moved to Sandia National Laboratories. She was elected American Physical Society (APS) fellow in 2001 and American Association for the Advancement of Science (AAAS) fellow in 2007. She served as a Member-at-Large on the APS Division of Materials Physics executive committee (2004–2007), on the Materials Research Society's (MRS) board of directors (2005–2007), the treasurer and chair of the operation oversight committee for MRS, and was on the editorial board for Solid State Communications. Hsu was chair of the APS Energy Workshop program committee in 2010. She is the chair of the MRS International Relations Committee.
Matthew T. Lloyd can be reached at the National Center for Photovoltaics, National Renewable Energy Laboratory, 1617 Cole Blvd., Golden, CO 80401, USA; tel. 303–384–7940; and e-mail firstname.lastname@example.org.
Lloyd is a scientist in the National Center for Photovoltaics at the National Renewable Energy Laboratory (NREL). He did his doctoral research at Cornell University on semiconducting small molecules for application in photovoltaics. Before joining NREL in 2009, Lloyd spent two years as a postdoctoral researcher at Sandia National Laboratories. His research focuses on the processing and properties of organic semiconductors and the physics of organic electronic devices. He is a member of the International Society for Optical Engineering and the Materials Research Society.