Dual Engineering Strategy of H Doping and S Grading for High Efficiency CIGSe Solar Cells

ABSTRACT Insufficient grain growth and unfavorable band structure are key issues that limit the performance of magnetron sputtering Cu(In,Ga)Se 2 (CIGSe) solar cells. Herein, a combined engineering strategy comprising bulk H doping and surface S grading is reported to achieve high‐efficiency CIGSe solar cells, in which H doping is introduced via reactively depositing CIGSe precursor under an H 2 ambient, while S grading is completed by depositing Cu(In,Ga)S 2 (CIGS) layer. H doping passivates dangling bonds and alleviates localized Na‐O clusters, facilitating grain growth and curbing native In Cu and V Se defects. S grading increases the surface S content and passivates grain boundaries, thereby widening the near‐surface bandgap and reducing carrier recombination. Synergistically, H and Na atoms activated by H doping inhibit Se out‐diffusion from the CIGSe absorber and S in‐diffusion from the CIGS layer, further diminishing surface defect density and mitigating electric potential fluctuations. Benefitting from the superior grain growth and the formed S gradient, a champion device with 18.69% conversion efficiency with a high V OC at 0.678 V is achieved. This work highlights the potential of a dual engineering strategy for increasing the performance of magnetron sputtered CIGSe solar cells and provides a feasible approach for their scalable industrial fabrication.