Current-matched triple-junction solar cell reaching 41.1% conversion efficiency under concentrated sunlight

A metamorphic Ga(0.35)In(0.65)P/Ga(0.83)In(0.17)As/Ge triple-junction solar cell is shown to provide current-matching of all three subcells and thus composes a device structure with virtually ideal band gap combination. We demonstrate that the key for the realization of this device is the improvement of material quality of the lattice-mismatched layers as well as the development of a highly relaxed Ga(1-y)In(y)As buffer structure between the Ge substrate and the middle cell. This allows the metamorphic growth with low dislocation densities below 10(6) cm(-2). The performance of the approach has been demonstrated by a conversion efficiency of 41.1% at 454 suns (454 kW/m(2), AM1.5d ASTM G173-03).