March 05, 2010
Understanding materials for photovoltaic applications
Silvana Botti has published with J. Vidal, P. Olsson, J.-F. Guillemoles and Reining an article entitled Strong interplay between structure and electronic properties in CuIn(S,Se)2: a first-principles study in the journal Physical Review Letters.
The thin films of CuIn(S,Se)2, used as absorbers in new generation photovoltaic technology, are generally deficient in copper. Despite significant deviations from stoichiometry and important concentration of default, these materials exhibit opto-electronic properties that are very stable. On the other hand, imperfections in the crystal can cause changes in crystal structure.
With an approach self-consistent GW, the authors studied the impact of the crystal structure, and more specifically of the variation on the width of the bandgap of these materials with internal parameters. They conclude that the distortions of the lattice and the presence of copper deficiencies have opposite effects on the size of the band gap and a compensation mechanism explains the relative stability of the experimental gaps. Methods beyond density functional theory are necessary to capture the physics of these complex systems.
Further information can be found here.