state is similar to the EV(ClO$_4$)$_2$+PEO mixture in powder form. This means that the device contains the EV$^{2+}$ form of viologen in the OFF state. Raman spectrum of the device in the ON state is different from its OFF state with some new peaks appearing and some disappearing. This certainly means that the species present in the ON and OFF states, giving rise to the Raman peaks, are different. It is also likely that the peaks appearing in the ON state are obtained as a result of reduction of the species present in the OFF state. To confirm this Raman spectra in Fig. 4 have been compared with the Raman spectra from EV$^{2+}$ and EV$^{\newmoon +  }$ as obtained by chemically reducing the EV(ClO$_4$)$_2$ using NaBH$_4$ which is shown in Fig. S3 in the SI. Comparison of Fig. 4 and Fig. S3 shows that the OFF device contains EV$^{2+}$ whereas the ON device contains EV$^{\newmoon +  }$ in majority which means that EV$^{2+}$ reduces to EV$^{\newmoon +  }$ as a result of applied bias more likely at the –ve electrode. This cannot be confirmed in the CBG because a spatial Raman spectroscopy is not possible.

To confirm this, in-situ Raman 