Hydrothermal assisted growth of vertically aligned platelet like structures of WO 3 films on transparent conducting FTO substrate for electrochromic performance

•Mixed phase obtained at 120 °C is transformed into single monoclinic phase at 180 °C.•WO3 film synthesized at 180 °C for 8 h reaction time exhibits high crystallinity.•Transmittance of 86% is achieved at 463 nm for WO3 film synthesized at 120 °C for 12 h.•WO3 film grown at 120 °C for 12 h shows relatively low resistivity of 1.8 × 10−3 Ω cm.