Study on the role of rGO in enhancing the electrochromic performance of WO3 film

In the present work, an improved electrochromic thin film has been developed with faster color switching time on incorporation of rGO in WO3 film. Here, pristine WO3 and rGO-WO3 (rGO concentration varying from 1-7wt %) based nanocomposite electrochromic films were fabricated on ITO coated glass substrate, by utilizing a facile sol-gel dip-coating technique. Detailed structural and morphological analyses of the films were carried out using XRD, FESEM, TEM and Raman Spectroscopy. Assimilating the electrochromic properties of all the films showed that, 5wt% rGO incorporated WO3 film gave a maximized electrochemical performance with minimum degradation in optical transmittance. The film also exhibited an optical modulation of similar to 50% and a better switching response having coloration time (t(c)) similar to 5.3 s and bleaching time (t(b)) similar to 6.2 s as compared to the pristine film (t(c) similar to 9.6 s, t(b) similar to 10.4 s). Incorporation of rGO also resulted in an enhancement of coloration efficiency from similar to 81 to similar to 386 cm(2)/C. The Electrochemical Impedance Spectroscopy (EIS) analysis of pristine and rGO loaded film clearly revealed better charge transfer on incorporation of rGO. The cyclic stability study exhibited similar to 25% deterioration in optical transparency of the bare WO3 film which was < 10% for the rGO impregnated film. An ex-situ XRD analysis demonstrated that a crystal dislocation occurring in pristine WO3 sample was responsible for the same.