Nanoelectronics Development of Nanostructured Solar Cells
Chalcopyrite, Cu(In,Ga)Se2 (CIGSe), materials have excellent light absorbing properties and are used in the thin-film solar cell technology with the highest power conversion efficiency. We are working with these materials at the nano- and micrometer length scale with the goal to increase power conversion efficiencies. Currently, we focus our research efforts on three topics:
• We aim to develop growth methods for chalcopyrite nanostructures, i.e. quantum dots and nanowires. The goal is to combine the excellent light absorbing properties of chalcopyrite-type materials with the quantum properties of nanostructured materials, and thereby provide a pathway for the enhancement of power conversion efficiencies of photovoltaic devices beyond the Shockley-Queisser limit. We use a molecular beam epitaxy (MBE) system to evaporate the constituent elements (Cu, In, Ga, Se) onto epitaxial substrates, where at low evaporation rates and thin coverage the formation of nano-sized crystallites occurs.
• We develop micro solar cells for micro-concentrator solar cell applications. The goal is to develop highly efficient solar cells with a significant reduction in usage of absorber materials. By concentrating the sunlight onto micrometer sized CIGSe solar cells, the materials consumption of the solar cell material can be significantly reduced, leading to cost improvements. We combine cleanroom technology with the growth of CIGSe materials to obtain the micro solar cells.
• Development of nanostructures for chalcopyrite thin-film solar cells. The goal is to use passivation and light management techniques to improve solar cell performance. We use cleanroom technologies to introduce a passivation layer with contact holes in between the back contact and the absorber layer. This reduces back contact recombination and allows for thinner absorber layers, leading to cost savings for solar cell devices.
Molecular Beam Epitaxy system for Cu(In,Ga)Se2 nanostructure growth