Dresden 2006 – scientific programme
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HL: Halbleiterphysik
HL 50: Poster II
HL 50.104: Poster
Thursday, March 30, 2006, 16:30–19:00, P3
III-V materials for multi-junction solar cells on the lattice constant of InP — •Ulf Seidel, H.-J. Schimper, U. Bloeck, K. Schwarzburg, F. Willig, and T. Hannappel — Hahn-Meitner-Institut, Glienicker Str. 100, 14109 Berlin
At present, the world record solar cell is a monolithic triple junction cell epitaxially grown on the lattice constant of GaAs or rather Ge. Considering the thermodynamic limit of the theoretical efficiencies of multi-junction cells with more than two band gaps there is a need of an appropriate material with a band gap in the range of 1eV.
For that, different III-V compound semiconductors were tested for application in multi-junction solar cells based on the lattice constant of InP, in particular InGaAs, GaAsSb (Egap = 0.75eV) and InGaAsP, InAlGaAs (Egap around 1.0eV). Solar cells consisting of these materials were grown via metalorganic vapor phase epitaxy (MOVPE) using the alternative precursors TBAs, TBP and TESb. An InP n/p cell was prepared as a reference and showed that highest internal quantum efficiencies were achieved using these nongaseous less toxic precursors. Single n/p cells with different absorber materials and nearly the same band gaps (0.75eV and 1.0eV) were compared to each other concerning short-circuit current, open-circuit voltage, FF, and quantum efficiency. Accordingly, a monolithic tandem solar cell was designed employing these sub cells for its application in a four or five junction cell as the low band gap part. Our tandem cell consists of an InGaAs bottom cell (Egap = 0.75eV) and an around 1eV InGaAsP sub cell. Connecting these two sub cells a new tunnel junction was produced including n-InGaAs and p-GaAsSb.