Thermochromic VO2 has received great attention for smart window application because of its ability to control solar heat gain in response to the temperature variations. It goes through a first order reversible phase transition from the semiconductor to metallic state at critical temperature of 68 degrees C, having higher infrared reflectance above this temperature. This paper summarizes some prominent theories behind this phase transition and presents a comprehensive review of recent progress in all-solution synthesis of VO2 thin film with a particular focus on sol-gel method. Emphasis is given to highlight different precursors exploited to prepare thin films with adjustable morphology and optimized optical properties. Actually, VO2-based coatings show good combination of integrated luminous transmittance (33.1-81.3%) and solar modulation ability (2.2-223%). The effect of various dopants such as tungsten, magnesium on thermochromic properties of VO2 thin films is also elaborated. These studies indicate that innovative solutions are essential to overcome the current shortcomings associated with practical application of VO2. (C) 2016 Elsevier B.V. All rights reserved.