## 4 Results and Discussion
### Without Compressing
The results that carbonyl group of Ni has a role of catalyst well-known at the field of macromolecular complex [19] provides the effect of Ni on MCF solar cell rubber. \[\mathrm{Ni}+2\;\mathrm{OH}\rightarrow\mathrm{Ni}^{2+}+2\mathrm{O}^{-}+ \mathrm{H}_{2} \tag{14}\]  
In general, TiO\({}_{2}\) is most often used in an ordinary dye-sensitized solar cell as an electron transport material [10; 11]. The interfacial electron-transfer process of TiO\({}_{2}\) in colloidal semiconductor systems has been reported [20]. Therefore, it is understandable that TiO\({}_{2}\) affects the photovoltaics, by looking at the case of \"MF, NR-latex, TiO\({}_{2}\) (2 g)\" in Figure 3b. In the case without electrolytic polymerization, indicated by \"No-elec.\" in Figure 3, Equations (3a) and (4) are replaced by Equations (15) and (16), respectively. \[\left[\mathrm{P}^{\mathrm{y}+}\mathrm{A}_{\mathrm{y}}^{-}\right]_{\mathrm{x}} \rightarrow\mathrm{P}_{\mathrm{x}}+\mathrm{xyA}\qquad\qquad\text{at anode of solar cell side} \tag{15}\]  
\[\left[\mathrm{D}^{+}\mathrm{P}^{\mathrm{y}-}\right]_{\mathrm{x}} \rightarrow\mathrm{P}_{\mathrm{x}}+\mathrm{xyD}\qquad\qquad\text{at cathode of solar cell side} \tag{16}\]  
In Figure 3, the curves of voltage and electric current density tended to slope downwards gradually when the light is turned off, compared to their trend when it was turned on. This can be explained by using the theoretical formation of the rate of electron-transfer reaction obtained from electron-transfer theory [21]. On the other hand, the tendency of the curves to slope downwards suddenly when the light was \"off\" and then recover slightly to become constant, in some cases, can be explained by using the long-range electron-transfer theory [22]--it is due to the changes in pH of the MCF rubber solar cell due to change in [H\({}^{+}\)] and [OH\({}^{-}\)] under the reactions of Equation (1), (2), (5), (6), and (14). When the potential at the particles of Fe\({}_{3}\)O\({}_{4}\) or Ni or molecules of polyisoprene becomes equivalent to that at an adjacent one from the state where their potentials are different, electron transfer is reversed because the electron can move to the orientation of smaller potential. The electron transfer is explained under the state of OSETR. In addition, the photovoltaic property of the MCF rubber solar cell resulted in a redox reaction as shown by Equations (1)-(4) and (6). The possibility of the above processes can be confirmed in an ordinary dye-sensitized solar cell, such as the Gratzel-type solar cell. It can be seen from Table 1 that there was an increase in the photoelectricity when oleic acid, MF, or TiO\({}_{2}\) were added to NR-latex, during the process of electrolytic polymerization in the magnetic field. It was greater for ultraviolet light than for visible light because TiO\({}_{2}\)-coated transparent glass reacts with the former: TiO\({}_{2}\) is a typical material reactive to ultraviolet light. Furthermore, the photovoltaic characteristics of the MCF rubber solar cell were investigated by an analysis of the current-potential curves. Figure 4 shows these curves for the types (A) and (B) of the cell without MK2 and KI + I\({}_{2}\) under illumination by ultraviolet light, for all the components of Figure 3. They were measured by a potentiostat (HA-151B, Hokuto Denko Co. Ltd., Tokyo, Japan) at 50-mHz scan rates in the potential domain of \(-\)1.5-1.5 V. It can be seen that the electric current changed rapidly at around the largest positive or negative potential for the component \"Elec., no-mag., Oleic acid, NR-latex\". This indicates a photodiode property and testified that MCF rubber had this property, derived from the combination of n- and p-type semiconductors corresponding to D and A, respectively, which was previously denoted in Section 2. The photodiode effect can be seen in organic optoelectronicdevices [23] and luminescent solar concentrators made of polysiloxane rubber [4]. However, there are few studies on photovoltaics of rubber-state photodiode.