Broadband and omnidirectional light harvesting is important in photovoltaic technology because of its wide spectral range of radiation and the sun's movement. This study reports the fabrication and characterization of zinc oxide (ZnO) dandelions on Cu(In,Ga)Se2 (CIGS) solar cells. The fabrication of dandelions involves the combination of self-assembled polystyrene (PS) nanospheres and the hydrothermal method, which is one of the simplest and cheapest methods of fabricating a three-dimensional, closely packed periodic structure. This study also investigates the optimization on dimension of the PS nanospheres using the rigorous coupled-wave analysis (RCWA) method. This study uses an angle-resolved reflectance spectroscope and a homemade rotatable photo I-V measurement to investigate the omnidirectional and broadband antireflections of the proposed dandelion structure. Under a simulated one-sun condition and a light incident angle of up to 60°, cells with ZnO dandelions arrays enhanced the short-circuit current density by 31.87%. Consequently, ZnO dandelions are suitable for creating an omnidirectionally antireflective coating for photovoltaic devices.