# On the Use of PEDOT as a Catalytic Counter Electrode Material in Dye-Sensitized Solar Cells
## 3 PEDOT in DSSCs
### PEDOT Based Alternative Counter Electrodes in DSSCs
#### 3.2.2 Alternative Redox Electrolytes
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**CE** & **Deposition Method** & **Redox Shuttle** & **Dye** & **PCE\%** & **[Ref.]** \\ \hline \multirow{4}{*}{**PEDOT-TSO**} & _spin coating_ & \(\mathrm{I_{3}}^{-}/\mathrm{I}^{-}\) & N719 & 4.60 & [51] \\  & _spin coating_ & \(\mathrm{I_{3}}^{-}/\mathrm{I}^{-}\) & Z907 & 4.1 & [49] \\  & _electrochemical_ & \(\mathrm{I_{3}}^{-}/\mathrm{I}^{-}\) & Z907 & 4.0 & [49] \\  & _spin coating_ & [Co(bpy)\({}_{3}\)]\({}^{3+/2+}\) & LEC4 & 6.3 & [18] \\ \hline \multirow{4}{*}{**PEDOT-PSS**} & _spin coating_ & \(\mathrm{I_{3}}^{-}/\mathrm{I}^{-}\) & N719 & 2.1 & [51] \\  & _electrochemical_ & \(\mathrm{I_{3}}^{-}/\mathrm{I}^{-}\) & Z907 & 4.2 & [49] \\  & _dip coating_ & \(\mathrm{I_{3}}^{-}/\mathrm{I}^{-}\) & N3 & 5.8 & [54] \\  & _scratch under IR light_ & \(\mathrm{I_{3}}^{-}/\mathrm{I}^{-}\) & N719 & 7.6 & [55] \\ \hline \multirow{4}{*}{**PEDOT-CIO4**} & _electrochemical_ & \(\mathrm{I_{3}}^{-}/\mathrm{I}^{-}\) & Z907 & 4.2 & [49] \\  & _electrochemical_ & [Co(dtb)\({}_{3}\)]\({}^{3+/2+}\) & Z907 & 1.49 & [17] \\  & _electrochemical_ & T\({}^{-}/\mathrm{T}_{2}\) & TH305 & 6.0 & [75] \\  & _electrochemical_ & [Co(bpy)\({}_{3}\)]\({}^{3+/2+}\) & MK2 & 4.2 & [76] \\ \hline \multirow{4}{*}{**PEDOT-TFSI**} & _electrochemical_ & \(\mathrm{I_{3}}^{-}/\mathrm{I}^{-}\) & N719 & 7.93 & [56] \\  & _electrochemical_ & \(\mathrm{I_{3}}^{-}/\mathrm{I}^{-}\) & C106 & 9.8 & [57] \\  & _electrochemical_ & T\({}^{-}/\mathrm{T}_{2}\) & C106 & 7.6 & [57] \\ \hline \multirow{4}{*}{**PEDOT-CI**} & _vapor_ & \multirow{2}{*}{\(\mathrm{I_{3}}^{-}/\mathrm{I}^{-}\)} & N719 & 8.42 & [58] \\  & _phasepolymerization_ & & & & \\ \hline \multirow{4}{*}{**PEDOT-FAP**} & _electrochemical_ & [Co(phen)\({}_{3}\)]\({}^{3+/2+}\) & Y123 & 9.5 & [64] \\  & _electrochemical_ & [Co(phen)\({}_{3}\)]\({}^{3+/2+}\) & Y123 & 10.3 & [64] \\  & _electrochemical_ & T\({}^{-}/\mathrm{T}_{2}\) & Z907 & 7.9 & [74] \\ \hline \multirow{4}{*}{**PEDOT-SDS**} & _electrochemical_ & [Co(bpy)\({}_{3}\)]\({}^{3+/2+}\) & LEC4 & 6.2 & [65] \\  & _electrochemical_ & [Cu(dmp)\({}_{2}\)]\({}^{1+/2+}\) & LEG4 & 8.3 & [68] \\  & _electrochemical_ & [Cu(tmpb)\({}_{2}\)]\({}^{1+/2+}\) & D35/XY1 & 11.3 & [70] \\  & _electrochemical_ & [Cu(tmpb)\({}_{2}\)]\({}^{1+/2+}\) & Y123/XY1b & 13.1 & [71] \\  & _electrochemical_ & [Cu(dmp)\({}_{2}\)]\({}^{1+/2+}\) & LEG4 & 7.9 & [72] \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Photovoltaic parameters of PEDOT-based DSSCs with various redox mediators and dyes under AM1.5 G illumination. thereby confirming the high photostability of the entire device, including PEDOT-based CEs [80]. Another important aspect concerning the long-term stability of PEDOT CEs can be related to the possible delamination of the coating that may be exacerbated by the high temperature that a solar cell must face in real outdoor applications. To tackle this issue, our group has investigated the chemical grafting of PEDOT to the surface of FTO glass. This approach consisted of the structural modification of the EDOT monomer by the insertion of a terminal aminopropyl-triethoxysilane (APTES), which was subsequently anchored to the FTO glass. The electrodeposition of PEDOT was performed following standard procedures on EDOT-functionalized-FTOs or un-modified FTO. Sonication and peeling tests confirmed that the new PEDOT-APTES CEs were more stable to delamination if compared to conventional PEDOT CEs. In addition, PEDOT-APTES based CEs displayed enhanced cell efficiencies, decreased charge transfer, and mass transport resistances with respect to both platinum and conventional PEDOT when tested in association to Co(III)/(II) couples [76].