Dr. Wolfgang Tress, LiU

Title
Device physics of organic solar cells

Abstract
Photovoltaic energy conversion is supposed to be one of the most promising amongst the “renewable” energy technologies. Research in organic photovoltaics  has made tremendous progress in the last decade. Organic solar cells reached a power conversion efficiency of 12 %. These devices are based on polymer and fullerene absorber materials. They are employed in an ultrathin nanostructured (10 to 100 nm) blend layer forming a so called bulk heterojunction. The working principle of these devices shows some fundamental differences compared to conventional semiconductor devices due to the localization and low mobility of charges. In this talk an introduction to the working principle of organic solar cells is given. The processes dominating the photocurrent and the origin of the photovoltage output are examined. A drift-diffusion model is applied to describe the current-voltage characteristics of a variety of devices. In particular, the role of the electrodes, drift- and diffusion currents, and charge carrier generation and recombination processes are discussed.