Dresden 2006 – scientific programme

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HL: Halbleiterphysik

HL 32: Photovoltaic

HL 32.1: Talk

Wednesday, March 29, 2006, 14:30–14:45, BEY 118

InP-based tandem solar cell with low band gaps — •U. Seidel, H.-J. Schimper, U. Bloeck, K. Schwarzburg, F. Willig, and T. Hannappel — Hahn-Meitner-Institute, Glienicker Str. 100, 14109 Berlin, Germany

III-V multi-junction solar cells already represent a kind of third generation solar cells and are currently the most efficient photovoltaic devices worldwide. In a multi-junction solar cell multiple single p/n solar cells with different band gaps are connected in series. At the present time the world record multi-junction cell is epitaxially grown on the lattice constant of GaAs or rather Ge. However, regarding the highest theoretical efficiencies there is a lack of an appropriate material with a band gap in the range of 1eV. A monolithic tandem solar cell with optimized low band gaps was designed for its application in a four junction cell as the low band gap part. It could be combined with a high band gap tandem or triple via different techniques. Our tandem cell was grown lattice-matched to InP via metalorganic vapor phase epitaxy (MOVPE). Only alternative precursors were used, i.e. TBAs, TBP and TESb. InGaAs (Egap = 0.75eV) was used for the bottom cell and InGaAsP for the absorber material around 1eV. To connect these two sub cells a new tunnel junction was produced including n-InGaAs and p-GaAsSb.