The short circuit current density (JSC) and the open circuit voltage (VOC) are two key factors that have critical influence on the performance of organic solar cells (OSCs). We have found that separating the donor and acceptor layer in bilayer OSCs with a thin insulating layer increases the energy of charge transfer (CT) state by weakening the Coulomb interaction at the interface and this also suppresses photoinduced CT and recombination. Although these effects usually increase VOC and decrease JSC, the trade-off is avoided by doping the insulating layer with a dye to utilize the energy transfer process. The increase in VOC without the reduction in JSC enhances the conversion efficiency of the OSCs by 30%.
Research Area: “Photoenergy Conversion Systems and Materials for the Next Generation Solar Cells”
Research Theme: “Precise Control of Organic Interfaces toward Highly Efficient Photovoltaic Processes”
Yufei Zhong, Akira Tada, Seiichiro Izawa, Kazuhito Hashimoto, Keisuke Tajima
“Enhancement of VOC without Loss of JSC in Organic Solar Cells by Modification of Donor/Acceptor Interfaces”
Advanced Energy Materials, Published online 22 Oct. 2013
Keisuke Tajima, Ph.D.
Team Leader, Center for Emergent Matter Science, RIKEN
Koji Matsuo, Masashi Furukawa, Natsuko Kawazoe
Green Innovation Group, Department of Innovation Research, JST