First‐Principles Studies of Electronic Structures and Optical Properties of Cobalt‐Doped VO2

First‐principles calculations based on density functional theory (DFT) are used to investigate the phase transition characteristics, electronic structures, and optical properties of pure and Co‐doped VO2 (M1 and R phase). Studies show that the metal‐to‐insulator phase transition temperature of VO2 is significantly reduced after Co doping, which is correlated to the decrease of bandgap value. Besides, the decrease of the energy required for electron transition of M1‐phase Co‐doped VO2 corresponds to the imaginary part of the dielectric peak moving to the low‐energy region. For both the M1‐ and R‐phase VO2, the visible light transmissivity of the Co‐doped VO2 is increased than that of pure VO2, which is beneficial to the application of VO2 film as visible windows. In addition, the absorptivity and reflectivity of Co‐doped R‐phase VO2 in the infrared light range are larger than those of M1‐phase VO2, indicating that the Co‐doped VO2 can block more infrared light at higher temperature to fulfill the purpose of lowering temperature. Overall, these results give new insights for the application of Co‐doped VO2 as a photoenergy material to regulate the room temperature.