WELLBUS · Study of Efficiency Enhancement Mechanisms in Quantum Well Solar Cells for Better Utilization of the Solar Spectrum (WELLBUS)

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Project objective

The GalnP/GaAs/Ge tandem triple junction cells are the highest efficiency photovoltaic (PV) devices and are likely to be the first of the Third Generation" cells to enter the terrestrial PV market in concentrator applications. They employ three different solar cells stacked on top of each other to capture and convert a wider spectral range of solar radiation to electricity. The commercial viability of concentrator systems depends crucially on the use of the highest efficiency cells. The Strain-Balanced Quantum Well Solar Cell (SB-QWSC) is an innovative, nanostructured cell, pioneered by the Quantum Photovoltaic Group (QPG) at Imperial College, which has the potential to enhance the efficiency of the triple junction cell significantly by replacing the GaAs cell. The SB-QWSC increases tandem efficiency by reducing the absorption band-gap of GaAs resulting in better utilisation of the solar spectrum. Recent experimental and theoretical work based onphotoluminescence (PL), photoconductivity (PC) and electroluminescence (EL) studies have revealed that the Quasi-Fermi Level Separation (QFLS) in single quantum well (SQW) devices is smaller than expected in both the dark and the light. This implies lower recombination and hence enhanced efficiency. Furthermore, the SB-QWSC dark currents at concentrator current levels show ideality factor n=1. This suggests that minimum non-radiative recombination levels can be achieved in SB-QWSC. Finally the exciting possibility of efficiency enhancement by photon recycling can also be considered as the unavoidable radiative energy would be re-absorbed in other wells in a light-trapping environment. There is therefore a great need to clarify the mechanisms behind the general efficiency enhancement in the SB-QWSC. This will be done by extending the recent studies on QFLS in SQW devices under light illumination to SB-QWSCs."

Original text from CORDIS.

Participants

• IMPERIAL COLLEGE LONDON · LONDONCoordinatorCity levelUnited Kingdom

Links

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