Evaluation of a combined CPV and TPV system under high DNI

Abstract

Concentrating photovoltaic systems (CPV) are usually composed of a Fresnel lens, and a three-junction two-terminal monolithically stacked solar cell. Stacking the sub-cells and the substrate monolithically raises the issue of the lattice and current matching. This issue limits the choice the materials and imposes optimization constraints. These constraints of current and lattice matching also exist in two-junction monolithically stacked solar cells. As a solution, an optical system is designed to keep the two quantum receivers apart while keeping the feature of converting different bands of the solar spectrum. In this paper, the design of a CPV system is presented. The system has two quantum receivers: a low bandgap cell which is sensitive to infrared radiation and another cell that has a high efficiency in the visible range of the solar spectrum, in addition to other optical components. The design shows an optical efficiency of 86.68 % and an overall conversion efficiency of 27 % while involving a GaAs (1.42 eV) and Ge (0.667 eV) single-junction solar cells.