Thisstudyinvestigatesvariouscopper-indium-gallium-selenium (CIGS) thin-film solar cells by adjusting the Ga component ratio ,defect density ,thickness ,and doping concentration of the absorption layer in simulations using the SCAPS software. The results are correlated with the carrier generation rate ,energy band alignment ,and electric field. The simulations indicate that for a thin-film solar cell prepared via single-step co-evaporation ,the energy-spike-like band alignment of the CIGS/CdS heterojunction facilitates carrier transport ,resulting in excellentoutput performance when the Ga content is30%. In contrast ,the output performance of a solar cell prepared via three-step co-evaporation exceeds that of a solar cell prepared via single-step co-evaporation due to the lower defect density of its absorption layer. Increasing the thickness of the absorption layer causes the 2. 0 μm-thick layer to absorb most ultraviolet-visible lightphotons ,butfurther increases decrease the short-circuit currentdensity. Moreover ,the open-circuit voltage and optovoltage of the solar cell increase with doping concentration ,while the short-circuit current and potential barrier of the CIGS/CdS heterojunction decrease. By optimizing the thin-film solar-cell parameters ,the photovoltaic conversion efficiency of the CIGS thin-film solar cellreached a maximum of27. 67%.