Double-absorber thin-film solar cell with 34% efficiency

Power-conversion efficiency is a critical factor for the wider adoption of solar-cell modules. Thin-film solar cells are cheap and easy to manufacture, but their efficiencies are low compared to crystalline-silicon solar cells and need to be improved. A thin-film solar cell with two absorber layers (instead of only one), with bandgap energy graded in both, can capture solar photons in a wider spectral range. With a 300-nm-thick CuIn 1 - ζ 1 Ga ζ 1 Se 2 absorber layer and an 870-nm-thick Cu 2 ZnSn (S ζ 2 Se 1 - ζ 2) 4 absorber layer, an efficiency of 34.45% is predicted by a detailed optoelectronic model, provided that the grading of bandgap energy is optimal in both absorber layers.