News Article
Spanish Institute achieves CSP efficiency of 39.2%
The Group of III-V Semiconductors of the Solar Energy Institute of the Technical University of Madrid (IES-UPM) in Spain has presented a concentrator solar cell with an efficiency of 39.2%, as confirmed by the Fraunhofer Institute for Solar Energy Systems in Freiburg (Germany).
After having successfully developed in 2008 a dual junction solar cell with an efficiency of 32.6% at 1026 suns "”a world record at that time"”the research group has focused its attention to the manufacturing of lattice-matched triple junction solar cells for ultra high concentration (1000 suns and above). The devices have an active area of 1 mm2 and consist of a GaInP-based top cell (TC) of ~1.9 eV, a GaInAs-based middle cell (MC) of ~1.4 eV and a Ge bottom cell (BC) of ~0.6 eV grown on Ge substrates. Concentration performance of the cell as measured at Fraunhofer ISE.
Concentration performance of the cell as measured at Fraunhofer ISE.
The measured cell shows a peak efficiency of 39.2% at a concentration of 398 suns, while the efficiency is still higher than 37% at 1000 suns.
The cell was manufactured by MOVPE at IES-UPM facilities and the semiconductor structure includes a high band gap GaInP/AlGaAs tunnel junction between the TC and MC. This tunnel junction is able to operate at concentrations higher than 15000 suns. Besides, the TC consists of a disordered GaInP, induced by the use of Sb during the epitaxial growth of the TC.
The whole cell is now being carefully optimized by using proprietary software and, in the near future, efficiencies higher than 42% are expected to be achieved at concentrations of 1000 suns.
The operation at 1000 suns or higher irradiances has been traditionally a goal for the Group of III-V Semiconductors of IES-UPM in order to achieve competitive electricity prices, well below those of 500 suns operation. Besides, a good performance of the cells at concentrations higher than 1000 suns is highly recommended in order to prevent the detrimental effects of the unavoidable non-uniformity of light impinging the solar cell in optical concentrators.
