LABRAM HR spectrometer using a 633 nm excitation source.

![Figure 3: CIE chart fitting of different intensity of a colour for device. Inset table is for the colour coordinate with respect to applied bias.](figure3){width="10cm"}

Results and Discussion
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Figure 1 is the combined pictorial representation of internal and external mechanism of CBG device. Fig. 1(a) shows cross sectional schematic view of CBG device with its biasing arrangement. Fig.1(b) is corresponding actual photographs of CBG device on various voltages. Fig 1(c) corresponds to proposed model which shows molecular dynamics and redox reaction within the device as a result of applied bias. Fig.1(a) shows that when external potential is 0 V, device is in its OFF state which corresponds to the transparent state and thus ‘IITI’ can be seen through the device clearly in Fig. 1(b). The transparency of the complete device reduces and becomes opaque after the application of -3.5 V bias as shown in Fig.1(b). Color change in viologen is a well reported phenomenon\[26\] and is often assigned to the different absorption/transmission properties exhibited by viologen species in its different oxidation states. Typical optical properties of chemically reduced viologen show that blue color originates due to the presence of EV$^{\newmoon 