Highly Efficient Double Graded CIGS Absorber Based Thin Film Solar Cell: A Numerical Study

This current work explores the numerical method of optimization for Copper Indium Gallium Selenide (CIGS) absorber-based solar cells. As the Ga/Ga+In ratio is one of the most important elements for the bandgap tuning of the CIGS absorber-based cell. It presents an opportunity to exploit the feature of the bandgap tunability of the absorber (CIGS) by altering the Ga/Ga+In ratio. A comparative simulation analysis was conducted on a double-graded (Notch Structure) CIGS solar cell, optimizing different parameters such as the band gap, the thickness, and the carrier concentration of the buffer layer and the absorber layer. Ga vs In ratio difference can bring on to conduction band offsets of two different categories a positive offset “spike” and a negative offset which results in a “cliff”, In which the offset of spike type is optimum in the range of O.leV to 0.4eV. To achieve optimum offset different alternative buffer options have been explored. To stop the Ga inter-diffusion among the absorber layer during the practical synthesis of device which involves high-temperature annealing. The intermediate layers p-MOS2 and p-MoTe2 have been proposed to stop Ga inter-layer inter-diffusion. The most efficient configuration involved ZnMgO as the buffer layer, with a p-MoTe2 intermediate layer between the CIGS absorber layers, yielding a fill factor of 77.82 % and a power conversion efficiency of η = 36.05%.