Regensburg 2007 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 5: Photovoltaic

HL 5.7: Vortrag

Montag, 26. März 2007, 12:30–12:45, H14

InP(100)-based low band gap tandem solar cell with an InGaAs/GaAsSb tunnel junction — •Ulf Seidel, Erol Sagol, Ulrike Bloeck, Klaus Schwarzburg, and Thomas Hannappel — Hahn-Meitner-Institute, Glienicker Str. 100, 14109 Berlin, Germany

Triple junction III-V solar cells lattice-matched to GaAs(100) and grown on a Germanium bottom cell have recently shown world record conversion efficiencies of 39% under concentrated sunlight. Even higher efficiencies can be expected when employing more than 3 junctions with optimized band gaps. However, to realize high-efficiency multi-junction solar cells with more than 3 junctions an appropriate absorber material with a band gap around 1eV is needed. Therefore, a monolithic low band gap tandem solar cell on the lattice constant of InP(100) was designed with optimized band gaps. It is thought to be combined with a GaAs-based high band gap tandem or triple cell via different techniques.

Here, we report on our results obtained when realizing an InP(100)-based low band gap tandem structure. The cell was grown monolithically on p-doped InP(100) via MOVPE in an AIX-200 reactor. The bottom cell (InGaAs E_g = 0.73eV) and the top cell (InGaAsP E_g = 1.03eV) of the low band gap tandem solar cell are connected via an Esaki-diode-like tunnel junction that includes n-InGaAs and p-GaAsSb. The influence of different preparation procedures on the critical InGaAs-GaAsSb hetero-interface and on the cell performance was investigated in detail.