## 3 Results
### Device Performance Metrics  
The electrochromic performances of these all-in-one gel based devices were further evaluated by switching them between alternating ON and OFF pulses with different voltages and times (Figure 2, Table S1). The transmittance contrast (\(\Delta\)%T), defined as the difference between the transmittance in the ON and OFF states, and the switching times, defined as the time required for reaching 90% of the full change in transmittance in a single switching time, are reported in Table S1. It is important to note that the voltage windows used correspond to the ranges where the monocations species are generated and reach their maximum intensity (\(\sim\)1430 and \(\sim\)670 nm, respectively), according to the spectroelectrochemistry of the devices. Figure 2 and Table S1 show that the TV/Fc system can reach, at \(\lambda\) = 670 nm, transmittance changes ranging from 74% to 82%. Analogous values, for the same absorption band, were found switching the TV/FD device. In this last, \(\Delta\)%T values ranging from 58% to 80% were found for the absorption band at \(\lambda\) = 1430 nm, depending on the V\({}_{\text{ON}}\) and its time of application (Figure 2, Table S1). For all the devices and for all absorption bands coloration times of few seconds (from 1.5 s to 5 s) and a little bit slower bleaching times (from 5 s to 8.5 s) were recorded. In order to compare the performance of the EC devices it is of noteworthy importance the correlation between the measurement of the charge passed during the oxidation and reduction processes and the transmittance change at a specific wavelength. This correlation parameter is known as coloration efficiency (CE, \(\eta\)). The \(\eta\) is given by the equation:  
\[\eta=\ \frac{\Delta OD}{Q_{i}}=log\ \frac{\left[\frac{T_{b}}{T_{c}}\right]}{Q_{i}} \tag{4}\]  
This also determines the amount of optical density change (\(\Delta\)OD) as a function of the injected/ejected electronic charge (Qi) per unit area. T\({}_{\text{b}}\) and T\({}_{\text{c}}\) are, respectively, the transmittance in the bleached and colored states. Figure 3 shows the change in optical density at three wavelengths (670, 890 and 1430 nm) as a function of the surface charge density. The CE value, extracted as the slope of the linear fitting of the reported curves, for both systems (TV/Fc and TV/FD), at 670 nm, is as high as 500 cm\({}^{2}\)/C, which is an outstanding result compared with analogous systems [51; 52; 53]. The CEs registered for the NIR bands in the TV/FD system, due to the electrogeneration of the TV\({}^{\bullet+}\)/FD\({}^{\bullet+}\) and TV\({}^{++}\)/FD\({}^{++}\) species, respectively, are 180 cm\({}^{2}\)/C and 170 cm\({}^{2}\)/C, thus, approximately three times smaller than that of the calculated at 670 nm and due to the formation of TV\({}^{\bullet+}\). Furthermore, the coloration efficiency of the band at 670 nm calculated for the TV/FD devices, is only slightly smaller than that calculated for the TV/Fc devices (490 cm\({}^{2}\)/C vs. 500 cm\({}^{2}\)/C), thus suggesting that the replacement of the ferrocene anodic component with the FD one, does not affect significantly the EC performances of the device in the visible wavelength range. Importantly, the coloration efficiency calculated at 1430 nm in the TV/Fc device is almost half that found in the TV/FD one (105 cm\({}^{2}\)/C vs. 180 cm\({}^{2}\)/C). Let's try to explain the above differences in the CE of the three bands. The infinitesimal change of absorbance \(dA\) at the wavelength of maximum absorption, at time \(t\), is given by the Equation (5):  
\[dA(t)=l\,\varepsilon_{+}dc_{+}(t) \tag{5}\]  
Figure 3: Optical density versus charge density of the EC devices containing the Fc/TV (electroactive area of 2.3 cm\({}^{2}\)) and MV/TV systems (electroactive area of 4 cm\({}^{2}\)). Figure 2: Representative Vis and NIR switching cycles of the devices showing the \(\Delta^{\circ}\)C as a function of the potential difference applied.