Light-trapping structure based on ultra-thin GaAs solar cell

Abstract

It is well-known that the light-trapping effect is very important for improving cell efficiency and reducing material cost. Certain kinds of light-trapping schemes have been explored and applied to thin-film cells, especially to Si-based thin-film solar cells. This is considered less attractive in GaAs thin film cells, due to the fact that GaAs has a high absorption coefficient, a direct bandgap and suffers from strong surface recombination. In this paper, we describe the development of a highly efficient light-trapping structure utilizing periodically patterned front and back dielectric nanopyramid arrays keeping a completely flat GaAs active layer. It was found that our proposed structure was superior for ultra-thin active layers. The optimized structure yielded a photocurrent density of 20.94 mA cm−2 with an active layer thickness of 0.1 μm, which by far exceeded the reference cell photocurrent of 15.31 mA cm−2 with an equivalent thickness. These results are very significant for directing research into the light trapping and cost reduction of thin-film GaAs solar cells.