Ga-Grading CIGS solar cell by one-step sputtering from a quaternary target without post-selenization

Construeting a Ga-grading profile in CIGS absorber has been a critical linchpin for boosting CIGS solar cell performance. However, rhe Ga was mobile thus easily segregated on the back site during the CIGS deposition, and especially occuned in co-evaporation and selenization with metallic precursor processes. Since the inhomogeneous Ga distribution within CIGS absorbers would be the limitation of efficiency, and the Ga-grading control is complicated, we proposed a promising process for stabilizing the Ga in CIGS absorber by one-step sputtering from a quaternary target. Furthermore, co-sputtering by GaiSes binary target and quaternary target was used to directly adjust the Ga-grading profile dunng the deposition. In this work, we validated that the one-step sputtering process from a CIGS quaternary target effectively mitigated the Ga segregation, and demonstrate an uniform distribution in lateral and planar direction. In addition, it is the first time that the Ga-grading of CIGS absorber by co-sputtering was proposed, and the preliminary results showed the 12.52% in conversion efficiency by the normal grading structure without post-selenization.