Analysis of Performance Limits in Current-Matched Tandem Solar Cells

Abstract

Tandem solar cells are at the forefront of extending the efficiency limits of solar cell technology. Among two-terminal tandems, current-matched (CM) tandem solar cells are of particular interest, owing to their relative ease of fabrication. Though CM tandems have been extensively studied, an analytical framework based on the detailed balance for N-layer CM tandems with area de-coupled subcells has not been addressed. Current matching constraints can be alleviated with the appropriate addition of area de-coupled subcells/modules at each layer. In this work, we propose an analytical framework for modeling the performance limits of an N-layer CM tandem solar cell with subcells across layers. Radiative coupling among cells is taken into account. Analytical expressions for the optimal number of subcells across layers are presented. Additionally, we investigate the impact of bandgap mismatches on efficiency, a critical factor in real-world fabrication due to material and processing variations, demonstrating that subcells enhance robustness against such imperfections. Our work provides useful design guidelines for designing and estimating the performance limits of advanced solar cell architectures and can be extended to voltage-matched and bifacial devices as well.