In this work, the low aspect ratio hexagonal close-packed dome arrays were designed to trap light for c-Si thin film solar cells. The optical performance of the designed solar cell was theoretically studied via simulation based on the rigorous coupled wave analysis in detail. The result of the simulation showed the model of the solar cell with arrays exhibited absorptivity enhancement in the longer wavelength range. Simultaneously, the integral for the AM 1.5 absorbance spectrum of each model showed that the absorption gains reach up to the highest point of 45.13% in the periodicity of 0.7 μm.