Thin-film high-efficiency solar cells (NAF.5492)

Within the project the Radboud University together with ECN and Dutch Space aim to reduce the costs of high-efficiency solar cells made of III-V compound semiconductors. This cost reduction is obtained by application of an Epitaxial Lift-Off (ELO) technique to separate the 2 µm thick solar cell structure as deposited by a gas phase deposition technique, from its expensive substrate which has a thickness of about 300 µm. A further reduction of expensive semiconductor material will be obtained by the application of cheap mirrors or lenses to concentrate the light that falls on an area many times (up to 1000 times) larger than that of the actual solar cells.

Parallel to the research for material reduction, the efficiency will be increased to more than 30% by the development of a tandem cell consisting of two different III-V cells e.g. a Gallium-Arsenide (GaAs) cell and an Indium-Gallium-Phosphide (InGaP) cell deposited on top of each other. In this respect one of the most important goals of the project is to develop thermally stable tunnel junctions as optically transparent, low resistivity, interdevice ohmic contacts between the two cells in the tandem structure.