High-performance sub-micron CIGSSe solar cells optimized for sodium doping by adjusting diffusion barriers

Alkali metal Na is beneficial to the performance of CuInGaSSe thin film solar cells. This work studies the addition and optimization of a sputtering SiO₂ barrier layer on the soda-lime glass to optimize the Na content that diffuses into the absorber layer from the SLG. The resulting Se content and distribution, the influence and change of the MoSe₂ thickness are studied. Also, the changes in quality of the p-n junction and the defects of the absorption layer are studied. Last, the resulting carrier separation and changes in the carrier recombination rate of each part of the absorber are analyzed. For sub-micron CuInGaSSe devices, it is clear that untreated soda-lime glass provides excessive amounts of Na. After optimization and analysis of the barrier layer thickness, the average conversion efficiency is increased by 34% compared with the sub-optimal sample, and the efficiency reaches 18.9%.