Nanowire Solar Cell Sensitized with II-VI Quantum Dot Layer

摘要

We report first results on a new solar cell consisting of a p-i-n hetero-junction formed between n-type transparent nanowires, undoped semiconductor quantum dots and a wide bandgap p-type polymer layer. The overall structure is SnO_2/ZnO/CdSe/MEH-PPV with MEH-PPV standing for poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene]. Microscopic studies on the structure of the quantum dot layer before and after anneal indicates a morphology change from a quantum dot assembly to a continuous polycrystalline thin film. The charge transfer between the absorber layer and the adjacent layers is improved as the layer is converted from the quantum dot assembly towards a polycrystalline thin film structure. In optimized devices the spectral photocurrent response shows contributions from the ZnO, the CdSe and the MEH-PPV, covering the spectral range from 300 to 700nm with an external quantum efficiency between 30 and 40%. The overall energy conversion efficiency approaches 1%.