## Effect of TiO\({}_{2}\) on Photovoltaics
### Chemical-Photovoltaic Mechanism  
#### 2.3.1 Case of Photovoltaic Mechanism by Dye and Electrolyte  
The ordinary chemical-photovoltaic mechanism of DSSCs is well known and can be expressed as Equations (1)-(5). At the cathode, the dye (Dye) is ionized to Dye\({}^{+}\) with TiO\({}_{2}\) coated on the transparent glass by illumination. Electrons from the dye enter the cathode through TiO\({}_{2}\), which serves as an electron transport body. At the anode, the electrolyte reacts as shown in Equation (1) by obtaining electrons from the anode. A part of \(I_{3}^{-}\) reacts as shown in Equation (2). \[3I_{2}+2e^{-}\to 2I_{3}^{-} \tag{1}\]  
\[2I_{3}^{-}+2e^{-}\to 3I^{-}. \tag{2}\]  
\(I_{3}^{-}\) on the right side of Equation (1) transfers to the cathode and reduces the ionized \(Dye^{+}\) at the cathode as shown in Equation (3). The dye on the right side of Equation (3) is ionized to \(Dye^{+}\) at the cathode again as above. \(I_{2}\) on the right side of Equation (3) transfers to the anode and reacts as shown in Equation (1). \[2 Dye^{+}+2I_{3}^{-}\to 2 Dye+3I_{2}. \tag{3}\]  
On the other hand, at the cathode, \(I^{-}\) on the right side of Equation (2) reacts via photoexcitation as shown in Equations (4) and (5) such that the electrons enter the cathode. \(I_{2}\) on the right hand of Equation (5) transfers to the anode and reacts as shown in Equation (1). \[3I^{-}\to I_{3}^{-}+2e^{-}. \tag{4}\]  
\[2I_{3}^{-}\to 3I_{2}+2e^{-}. \tag{5}\]  
The above chemical-photovoltaic mechanism can be applied to ordinary DSSCs which are wet-type solar cells with liquid electrolyte and dye without any solid material. However, we can obtain the photovoltaic effect even if we use a conventional rubber sandwiched between the dye and the electrolyte solution, as shown in Figure 7 and in a previous study by [PERSON] [29]. As a liquid, in general, cannot be percolated through a rubber, the creation of the photovoltaics might be due to the electrons and ions transferring over the rubber surface. In contrast, in the case of the MCF rubber DSSCs, a liquid can be percolated through MCF rubber as shown in Figure A2 in Appendix A, as presented in our previous study [41]. Therefore, the above chemical-photovoltaic mechanism occurs within the MCF rubber. 3.2 Case of Electrical-Chemical Mechanism before Electrolytic Polymerization and without Light Scattering  
From our water-soluble rubber in the form of NR or CR structured by polyisoprene molecules in the MCF rubber, one unit of isoprene molecules is defined as \(SH\) with presenting \(S\), as shown in Equation (6). Without electrolytic polymerization, \(SH\) is anionized to \(S^{-}\), as shown in Equation (7), via the Honda-Fujishima effect [30; 47]. \[SH\leftrightarrow\left(SH\right)^{*}\leftrightarrow\left(S^{-}H^{+}\right)^{*} \leftrightarrow\left(S^{-}H^{+}\right)\leftrightarrow S^{-}+H^{+}. \tag{7}\]  
\(S^{-}\) generates a radical \({}^{\bullet}\) as shown in Equation (8) via some influences such as illumination. \[S^{-}\to S^{\bullet}+e^{-}. \tag{8}\]  
Water molecules are ionized as shown in Equation (9) [51]. \[H_{2}O\to H^{+}+OH^{-}. \tag{9}\]  
The generated radical \(OH^{-}\) becomes a hydroxyl radical \(OH^{\bullet}\) as shown in Equation (10) due to certain influences. \[OH^{-}\to OH^{\bullet}+e^{-}. \tag{10}\]  
3.3 Case of Electrical-Chemical Mechanism by Electrolytic Polymerization and without Light Scattering  
The reaction occurs as shown in Equation (11) at the anode via electrolytic polymerization [38]. \[SH+S^{-}\to SS+H^{\bullet}+e^{-}. \tag{11}\]  
\(SS\) denotes cross-linking between isoprene molecules. The reaction occurs as shown in Equation (12) at the cathode, when the oleic acid coating around Fe\({}_{3}\)O\({}_{4}\) is defined by \(P\) as shown in Equation (13) [38]. \[2I_{3}^{-}+2e^{-}\to 3I^{-}. \tag{2}\]0  
\[P\equiv \begin{array}{c}C_{17}H_{33}\end{array}  \tag{13}\]  
The electrons on the right side of Equations (10) and (11) transfer into the anode.