Thin film approaches for high-efficiency III–V cells

By analyzing the internal recombination losses in state-of-the-art GaAs solar cells, we demonstrate that such cells are approaching a material limit efficiency. Two new designs for III–V cells are then proposed and analyzed; both approaches make use of thin epitaxial layers. The first approach is to make use of light-trapping techniques to reduce volume recombination losses while maintaining the short-circuit current. Projections show that light trapping might add 2%–3% in efficiency. A second approach is to trap photons emitted during radiative recombination in order to enhance the bulk lifetime. With this approach, a 2% gain in efficiency is projected. These new design approaches will require the development of techniques for producing and processing thin epitaxial layers of GaAs, but they promise substantial gains in the efficiency of single-junction cells.