Crystalline organic thin films with large exciton diffusion lengths for high efficiency organic solar cells.

In this project we want to establish a basis for a new generation of low-cost organic solar cells. Organic solar cells are made by deposition of organic semiconducting films, which in turn consist of several layers of organic (i.e. carbon-based) molecules. Usually, this deposition leads to the formation of amorphous or polycrystalline films. However, measurements on individually hand-picked organic single crystals show greatly improved charge carrier transport and exciton diffusion. We therefore set out to develop a process to deposit high-quality crystalline films with a process compatible with large scale solar cell production. As a starting point, we use an abrupt heating method which was developed for rubrene transistors. We already showed this method can produce crystalline rubrene thin films on several substrates, including the indium tin oxide covered glass substrate typically used for organic solar cells. In a next step, we will make these optically thin films thicker by growing extra, epitaxial layers of rubrene on top, and investigate the possibility to use these crystals as templates for crystalline heterojunctions. Furthermore, we will develop an understanding of crystalline film formation to generalize the process for materials other than rubrene.The resulting multi-crystalline films will be used to fundamentally investigate exciton diffusion, and will be integrated into high efficiency, state-of-the-art organic solar cells.

Keywords:Exciton diffusie, Zonnecellen, Organisch, Rubreen, Kristalgroei

Disciplines:Condensed matter physics and nanophysics