## 4 Results and Discussion  
### Without Compressing  
First, the photovoltaics, without compression, were examined in order to understand the physical mechanism of the MCF rubber solar cell. Figure 3 shows the changes in voltage and electric current density when ultraviolet light was turned on and off, designated by colored arrows in the figure. The data are for types (A) and (B), without MK2 and KI + I\({}_{2}\). They exhibited photoelectricity (photovoltage and photocurrent), including built-in electricity (built-in voltage and  
Figure 2: Schematics of the MCF rubber production procedure to create solar cell. current). The former was due to a change of start-up voltage or electric current due to incident light and the latter was the initial voltage or electric current. The built-in voltage suggests the occurrence of the piezoelectric effect. In addition, due to the reason described in (b-3) of Figure 1, built-in current also occurred when these were removed initially in some cases of the data of Figure 3. The cause was the integrated data at microscopic part of adjacent particles or molecules, of which the state corresponded to dispersion as shown in (b-1) of Figure 1.  
The magnitude of photoelectricity, excluding the built-in electricity, due to irradiation by visible and ultraviolet light is shown in Table 1.  
The photoelectricity was very small in the case of electrolytically polymerized NR-late without the application of magnetic field. Photoexcitation owing to C=C bonds in polyisoprene was very minimal. In contrast, it is clear that the mixture of NR-latex and oleic acid was photovoltaic, whether it was electrolytically polymerized or not, by looking at the case of \"Oleic acid, NR-latex\". This was due to the ionized polyisoprene, which (as shown by the second term on the LHS of Equation (1)) played the role of an acceptor-like p-type semiconductor (corresponding to A\({}^{-}\) in (a-1) of Figure 1), and due to the hydrogen ion decomposed from water molecules in NR-latex and MF (see second term in LHS of Equation (2)), which played the role of donor-like n-type semiconductor (corresponding to D\({}^{+}\) in (c-1) of Figure 1). Therefore, the NR-latex and oleic acid in MCF rubber produced a photovoltaic effect. In addition, since MF included oleic acid, the mixture of NR-latex and MF was photovoltaic, by looking at the case of \"MF, NR-latex\". The results show that oleic acid had a role of catalyst as a bridging ligand on ISETR in the field of macromolecular complex [18], which was the effect of oleic acid on the MCF rubber solar cell. On the other hand, like the configuration of p- and n-type semiconductors, and the formation technique of organic photoelectric conversion elements in an ordinary solid-state solar cell such as  
Figure 3: Change in voltage and electric current density by turning ultraviolet light on and off: (**a**) voltage; (**b**) electric current density. “elec.”, electrolytic polymerization; “mag.”, with magnetic field at electrolytic polymerization; “no-”, without one. Each color indicates a component of the MCF rubber solar cell made of types (A) and (B), without MK2 and KI + I\({}_{2}\). an organic polymer film solar cell, many magnetic clusters indicated by (b) in Figure 1 form the bulk hetero-junction structure. Although the MCF rubber solar cell is a mixture of p- and n-type semiconductors, etc., unlike the layered structure of the components in a solid-state solar cell, the bulk hetero-junction structure exists as shown in (b) in Figure 1. Therefore, focusing on the cases of \"MF, NR-latex\" and \"Ni, MF, NR-latex\", photocurrent density in \"mag.\" decreased more than that in \"no-mag\". The comparison between the cases of \"MF, NR-latex\" and \"Ni, MF, NR-latex\" denotes the effect of metal particle on photoelectricity. There is a possibility that Ni reacts with surface hydroxyl group of oleic acid of MF as in Equation (14).