+  }$ species which can be obtained by chemically reducing EV$^{2+}$ (present in ethyl viologen diperchlorate) which is transparent. Alternatively, similar redox change can be induced in the material in the form of a solid state device as a result of electrical bias which provides the basis for an electronic electrochromic device.

![Figure 4: In-situ Raman spectra in ON and OFF state of device in cross-bar geometry. Insets show actual photographs of the device in its ON and OFF states.](figure4){width="10cm"}

Mechanism responsible for bias induced color change as shown in Fig1 (b) can be understood as follows. When potential is applied, electrons are supplied by the power supply and infusion of electron take place into the compound which may be reducing the viologen molecules near the -ve electrode to get the opaque (ON) state when most of the viologen molecule gets reduced. EV$^{2+}$ and ClO$^{4-}$ species (in PEO matrix) are randomly distributed in between the two ITO electrodes in the absence of bias (V=0). When bias is applied (V = -1V) electrons supplied by the –ve electrode is accepted by EV$^{2+}$ to get reduced to EV$^{\newmoon +  }$ to initiate the color change. As higher voltages are applied more reduction 