Analysis for Efficiency Potential of II-VI Compound, Chalcopyrite, and Kesterite-Based Tandem Solar Cells

The development of high-performance solar cells offers a promising pathway toward achieving high power per unit cost for many applications. As single-junction solar cells are limited to 30-32% conversion efficiency under 1-sun, multi-junction or tandem solar cells are expected to contribute to higher performances. The II-VI compound, chalcopyrite, and kesterite-based tandem solar cells are expected as high-efficiency and low-cost solar cells. This paper presents analytical results for efficiency potential and loss elements of II-VI compound, chalcopyrite, and kesterite-based tandem solar cells. The 2-junction and 3-junction tandem solar cells have potential efficiencies of 36% and 42%, respectively, by improving external radiative efficiency and reducing resistance and optical losses. Some paths for improving efficiencies of tandem solar cells are shown by analyzing their loss elements. Optimization of band-gap energy of sub-cells and photon recycling are also recommended.