Researchers improve efficiency and stability of organic solar cells

A German-Chinese research team has developed a process that is intended to improve both the efficiency and stability of organic solar cells. This would lead to progress in the two main problem areas that have so far stood in the way of a broad application of this technology.
In an article for the journal »Angewandte Chemie« (Applied Chemistry), the team led by Frank Würthner from the University of Würzburg and Zengqi Xie from the South China University of Technology in Guangzhou describe a process in which they made the zinc oxide layer used in many organic cells between the (inorganic) negative electrode and the (organic) active layer of the cell »somewhat more organic and conductive under light«. They prepared the organic dye »Hydroxi-PBI« in such a way that it forms stable complexes with the zinc ions in the zinc oxide layer. Under sunlight, the Hydroxy-PBI can increase the conductivity of the zinc oxide layer by feeding electrons into the layer.
The structure of the cell in the form of an »inverted bulk heterojunction architecture« consists of an indium tin oxide glass electrode, the Hydroxy-PBI-doped zinc oxide layer, the active layer of a polymer as electron donor and an organic molecule as acceptor. In addition, there is another metal oxide intermediate layer and an aluminum electrode as positive electrode. »Under optimal conditions«, this should enable efficiencies of up to 15 percent.
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