The design and development of new advanced materials or technologies are essential for the construction of high performance smart windows for the next generation of energy efficient buildings. Tungsten trioxide (WO3) based flexible electro-chromic devices f-ECDs have received extensive attention for the development of next generation f-ECDs. Here, we demonstrated the design and fabrication of kiwi fruit peel derived carbon dots (KF-CDs) decorated WO3 films under benign approaches. Furthermore f-ECDs were developed and their performance have been examined in terms of transmittance and coloration efficiency. The amount of KF-CDs in to the WO3 was varied and optimized f-ECDs exhibited the excellent optical contrast (ΔT) of 83.74 %, coloration efficiency of 86.2 cm2/C. The optimized f-ECDs exhibited excellent cyclic stability of 25000th cycles and retained more than 80 % optical contrast compared to the initial performance. This improved stability may be attributed to the presence of strong hydrogen bonding between the functional groups of KF-CDs and WO3.