## 3 Results and Discussion
### Electrochromic Switching Characteristics
For the WO\({}_{3\,|}\)comp and WO\({}_{3\,|}\)mp films, the transmittance started to change during the intercalation step at a more negative potential of around \(-0.25\) V compared to films of WO\({}_{3\,|}\)mp400, WO\({}_{3\,|}\)mp600 and WO\({}_{3\,|}\)mp (Figure 6b). Such a delayed change in transmittance indicates a slower initial intercalation of the ions within the WO\({}_{3\,|}\)comp and WO\({}_{3\,|}\)mp films. For both films, the CV curves at the first cycle (Figure 6a) also stay at smaller current and show a small peak at around \(-0.4\) V and \(-0.7\) V, respectively. Such characteristics are expected for a hindered reaction, typically observed for crystalline WO\({}_{3}\) films [33] but observed here for the amorphous WO\({}_{3\,|}\)comp and WO\({}_{3\,|}\)mp films, indicative of an initial barrier for ion intercalation in line with the compact film structure or the presence of remaining polymer fragments. Nevertheless, from \(-0.25\) V to \(-1.0\) V the slope of the transmittance is comparable for all the films. During the bleaching process, however, a significantly steeper slope of the transmittance-potential curves can be observed for films of WO\({}_{3\,|}\)mp400, WO\({}_{3\,|}\)mp600 and WO\({}_{3\,|}\)mp suggesting a significantly more facile deintercalation of Li\({}^{+}\) through the porous film network. Figure 7: Transmittance spectra of (**a**) WO\({}_{3\,|}\)mp600 and (**b**) WO\({}_{3\,|}\)mp thin films measured in contact to LiClO\({}_{4}\) in PC at a scan rate of 5 mV s\({}^{-1}\) in the initial state (init. ), in the bleached (1 V) and in the colored (\(-1\) V) states. The insets show the calculated color impressions for the second cycle of the films. Another important parameter for the comparison of switching characteristics of the electrochromic films is provided by the coloration efficiency _CE_. It is defined as the change in optical density \(\Delta OD\) with the intercalated charge density \(q\) (see Equation (2)) [2,7]. _CE_710 nm of the films at 710 nm, a wavelength for which the change was most significant, was determined from a linear fit in a plot of \(\Delta OD\) = log\(T_{\text{bleach}}\) - log\(T_{\text{col}}\) over \(q\), the charge inserted during the switching process. \[CE=\frac{\Delta OD}{q} \tag{2}\]  
_CE_710 nm for the WO31 up400, WO31 up600 and WO31 up7 films was found considerably higher than for WO31 comp or WO31 mp (Table 8). Less charge is needed to allow a high transmittance modulation for the films with interconnected micropores compared to the compact or just mesoporous films. Such enhancement of _CE_ by using appropriate structure-directing agents is in good accordance with earlier reports [27,31]. The highest obtained values for \(\Delta T_{\text{710 nm}}\) and _CE_710 nm for the porous films were reached for WO31 up, similar or even better than those measured for commWO3, the commercial benchmark sample, speaking in favor of the present films with a combination of mesopores interconnected by micropores. Interestingly, the _CE_ values reported here are significantly higher than those previously reported for WO3 films with ordered spherical mesopores caused by a similar block copolymer, and also similar thickness [34]. The observed higher _CE_ in the present study is indicative of differences in the pore space: the mesoporous films reported in [PERSON] et al. [34] were prepared without additional PEG and, thus, without the improved connectivity between the spherical mesopores in WO31 up. Hence, this comparison clearly supports the need for connecting micropores to maximize the electrochromic response. CV measurements were also performed for WO31 comp and WO31 up600 following their annealing at temperatures higher than 250 \({}^{\circ}\)C (Table S1).