Broadband antireflection of dielectric composite nanostructures on the surface o f single-junction GaInP solar cellsis demonstrated through rigorous coupled-wave analysis (RCWA) method.A systematic simulation of the effect on br oadband antireflection,normalized abso rption and ultimate efficiency of the dielectric composite nanostructures decorated solar cells was done.Therein,the se dielectric composite nanostructures consist of SiO_2nanocones and their underlying thin films,including SiO_2and SiNx dielectric layers.The optimized dielectric composite nanostructures are achieved by the systematically simulation of their duty circle,aspect ratio,the underlying material and its thickness.The results show that the ultimate efficiency of 28. 58% is achieved when the diameter of the SiO_2nanocone the height of the SiO_2nanocone and the thickness of the under lying SiNx dielectric layer are 550nm,650nm and 60nm,respectively.Such an investigation provides a valuable guidance for th ese solar cells to achieve higher conversion efficiency through surface decorati on.