Photovoltaic-performance-enhancing patch with combined light trapping and spectral upconverting effect

In this article, we demonstrate a patch, which contains upconverting crystals of Gd2O2S:Yb3+, Er3+ mixed with a UV curable gel, integrated with a textured back-reflector that can be externally affixed to a bifacial thin-film silicon solar cell. The patch serves to provide the benefit of light trapping as well as spectrum upconversion to the solar cell fabricated on a flat substrate. Upconverting patches with different textures were studied for their effectiveness in enhancing the short-circuit current density of the solar cell and for the relationship between the current enhancement and the intensity of the incident light. The upconverting patch is shown to enhance the solar cell performance and offers a new stick-on technique to apply upconversion-based strategies to existing solar cells. The photogenerated short-circuit current densities of the solar cell show a power-law dependence on the illuminated laser light intensity when an upconverter patch is attached to the solar cell (exponent 1.5-1.6) while a linear dependence is observed for the solar cell without the upconverter patch.