Stephanie Essig1 Jaime Castillo-León1 Mikael Björk1 Ingvar Åberg1

1, Sol Voltaics AB, Lund, , Sweden

A steady increase in new photovoltaic installations and thus a rising contribution of solar energy to the world-wide energy production can only be ensured by a continuous reduction of the $/Watt costs for photovoltaic systems. Silicon single-junction solar cells are close to reaching their practical efficiency limit which will boost the need for higher-efficient photovoltaic technologies. Efficiencies over 30% were demonstrated by combining Si solar cells with wide-bandgap III-V top cells. Despite these impressive efficiencies, the application of solar cells including III-V semiconductors has been limited by the high fabrication costs mainly caused by the MOCVD growth and required substrates. Other, potentially lower-cost top cell materials like perovskite semiconductors have so far not been able to reach tandem cell efficiencies of 30%. The costs of III-V top solar cells can be drastically reduced when using GaAs nanowire arrays fabricated by Aerotaxy™. Due to the superior geometry, high theoretical single-junction efficiencies of >25% can be achieved for an area coverage of <20%, enabling tandem cell efficiencies over 30% when applied in a tandem cell with Si bottom cell. The fabrication by Aerotaxy™ [1] does not require a growth substrate, allows an efficient use of the precursors and is conducted at higher throughputs. In this presentation, more insights into the concept of low-cost GaAs nanowire/Si tandem solar cells will be given and the great potential of this innovative technology will be discussed.

[1] M. Heurlin, M. H. Magnusson, D. Lindgren, M. Ek, L. R. Wallenberg, K. Deppert, L. Samuelson,
”Continuous gas-phase synthesis of nanowires with tunable properties”, Nature 492, p. 90–94, doi:10.1038/nature11652