NOVELTY - Nanophotonic composite structure comprises e.g. a nanophotonic structure with high-efficiency light trapping function, a passivation layer for inhibiting non-radiative recombination, a nano-textured sub-wavelength wide-angle antireflection layer and at least a one-dimensional grating, a two-dimensional grating or a three-dimensional photonic crystal, where the thin-film solar battery is composed of a surface layer as sunlight energy absorption material and a battery base unit below the surface layer and the nanophotonic composite structure on the surface layer.    USE - The nanophotonic composite structure useful for increasing absorption efficiency of thin-film solar battery.    ADVANTAGE - The nanophotonic composite structure: has functions of light trapping, non-radiative loss inhibiting and wide angle antireflection; and improves conversion efficiency of the thin-film solar battery.    DETAILED DESCRIPTION - Nanophotonic composite structure comprises a nanophotonic structure with high-efficiency light trapping function, a passivation layer for inhibiting non-radiative recombination and a nano-textured sub-wavelength wide-angle antireflection layer and at least a one-dimensional grating, a two-dimensional grating or a three-dimensional photonic crystal, where etching shape and etching depth of each grating or photonic crystal meet the requirement that diffraction angle of photon in surface layer of the thin-film solar battery is greater than full reflection critical angle, and the thin-film solar battery is composed of a surface layer as sunlight energy absorption material and a battery base unit below the surface layer and the nanophotonic composite structure on the surface layer. An INDEPENDENT CLAIM is also included for preparation of the nanophotonic composite structure, comprising (i) preparing nanophotonic structure graphic template with light trapping performance on the solar battery surface layer, then (ii) transferring the nanophotonic structure graphic template to the surface layer by etching or embossing, forming nanophotonic structure meeting the requirement that diffraction angle of photon in surface layer of solar battery is greater than full reflection critical angle on the surface layer, (iii) keeping nanophotonic structure on the surface layer, completely removing nanophotonic structure graphic template on the surface layer, then (iv) keeping optical performance of the surface of the nanophotonic structure, and passivating the surface of the nanophotonic structure by at least one of chemical method surface modification, plasma reinforced chemical gas-phase deposition, thermal oxide deposition and atom layer deposition, and (v) preparing sub-wavelength wide-angle antireflection layer on the passivated surface of nanophotonic structure, where the method is suitable for use after preparing solar battery forming material.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic representation of the nanophotonic composite structure.