Chapter 5. Recent Progress in Quantum Well Solar Cells

Quantum well solar cells are the result of the application of nanotechnology to enhance of the efficiency of concentrator solar cells. The band gap of a quantum well (QW) solar cell can be adapted to the incident spectral conditions by tailoring the QW depth. The single-junction strain-balanced quantum well solar cell (SB-QWSC) has achieved an efficiency of 28.3%. The dominant loss mechanism at the high concentrator cell operating bias is due to radiative recombination, so a major route to further efficiency improvement requires a restriction of the optical losses. It has been found that (100) biaxial compressive strain suppresses a mode of radiative recombination in the plane of the QWs. As biaxial strain can only be engineered into a solar cell on the nanoscale, SB-QWSCs are seen to have a fundamental efficiency advantage over equivalent bulk cells. Strain-balanced quantum wells in multi-junction solar cells can current match the sub-cells without the introduction of dislocations. Quantum-well (QW) technology was proved to boos the efficiency of triple-junction cells by around 3 percent in absolute terms. In fact 40 percent median efficiency has been achieved across production wafers.