Vanadium dioxide (VO 2) is a promising material for thermochromic glazing. However, VO 2 thermochromic smart windows suffer from several problems that prevent commercialization: low luminous transmittance (T lum) and low solar modulation ability (ΔT sol). The solution to these problems can be sought from nature where the evolution of various species has enabled them to survive. Investigations into the morphology of moths eyes has shown that their unique nanostructures provide an excellent antireflection optical layer that helps moths sharply capture the light in each wavelength from a wide angle. Inspired by this mechanism, a VO 2 thermochromic smart window coated with a TiO 2 antireflection layer with a novel nano-cone structure, is presented in this study to achieve high T lum and ΔT sol. Optimization for the key structure parameters is summarized based on the FDTD numerical simulations. The optimized structure exhibits a T lum of 55.4% with ΔT sol of 11.3%, an improvement of about 39% and 72% respectively compared to the VO 2 window without an antireflection layer. Furthermore, wide-angle antireflection and polarization independence are also demonstrated by this nano-cone coating. This work provides an alternative method to enhance the optical performance of VO 2 smart windows. Energy and environmental problems have become critical issues in modern society. It has been proven that buildings consume 20-40% of the total energy used. Most importantly, 60% of that energy is consumed to maintain thermal comfort by heating, ventilation and air conditioning (HVAC) systems 1. The huge consumption of energy by HVAC systems is mainly due to heat loss through the building envelope such as the roof, walls and windows. Among these building envelopes, approximately 50% of the energy is lost through windows, so more attention has been focused on energy efficient windows 2. Thermochromic smart windows are widely investigated because of their low cost and passive controllability of solar irradiance 3. Vanadium dioxide (VO 2) is one of the thermochromic materials to modulate transmittance of solar radiation because of its internal reversible phase change from metal (hot state) to insulator state (cold state) at a critical transition temperature of 68 °C 4. The phase change gives rise to an abrupt change of the near-infrared (NIR) transmittance, which renders VO 2 a promising candidate for thermochromic smart windows. To fulfill the demand of human vision and energy efficiency, improving luminous transmittance (T lum) and solar modulation ability (i.e. the difference of solar transmittance (T sol) between cold and hot states of materials or ΔT sol) simultaneously are key for the practical applications of VO 2 smart windows in buildings 5. Many efforts have been made to improve T lum and ΔT sol of thermochromic smart windows, such as chemical doping 6,7 , synthesizing VO 2 nanoparticles 8-11 and morphology modification 12-15. Among the different methods, depositing a planar antireflection layer is a commonly used solution to achi...