Performance Enhancement of Organic Photovoltaic Cells by Doping Techniques

Organic photovoltaic (OPV) cells have distinct advantages, including light weight, compatibility with flexible substrates, and low production costs. An unprecedented power conversion efficiency of 5% has been recently achieved; however, further improvements are needed to meet specifications required for commercialization. The efficiency of OPV cells can be improved by (i) maximizing optical absorption, (ii) enhancing exciton dissociation efficiency, and (iii) improving photocurrent collection by reducing the series resistance. In this project, doping techniques will be exploited to improve the efficiency of OPV cells via these three approaches. In particular, the influences of metallic and molecular dopants including fluorescent and phosphorescent dyes on the performance of OPV cells will be systematically studied. Preliminary findings of the investigator demonstrated that doping suitable metals or fluorescent dyes in appropriate organic layers can significantly increase the power conversion efficiency of OPV cells. However, mechanisms for efficiency enhancement remain unclear. The project aims to understand the determining factors and underlying physics of the enhancement effects of different doping approaches. The findings are expected to provide useful guidelines for material selection and design of novel cell structures with improved performance.