## 4 Tension and Compression Experiments
Figure 9: Schematic diagram of experimental apparatus for measuring photoelectricity and piezoelectricity of wet-type MCF rubber solar cell under tension and compression: (**b**) is viewed at an angle on (**a**). Figure 11: Changes in the electrolytic polymerization effect due to tension under irradiation with ultraviolet light: (**e**) represents the relation between the tensile strength and elongation; elongation rates in various cases (**a**–**d**) for wet-type MCF rubber solar cell electrolytically polymerized under a magnetic field with Ruthenium complexes dye and electrolyte KI + I\({}_{2}\). Secondly, we investigated the effect of magnetic clusters on tensioned and compressed MCF rubber solar cells. By fabrication magnetic clusters, the hetero-junction structure was obtained in the  
Figure 12: Changes in the effect of magnetic clusters by tension under irradiation with ultraviolet light: (**e**) shows the relation between the tensile strength and the elongation for the various cases from (**a–d**) for wet-type MCF rubber solar cell electrolytically polymerized under a magnetic field with Ruthenium complexes dye and electrolyte KI + I\({}_{2}\). solar cell. Figure 12 compares the effect of the hetero-junction structure on the photoelectricity and built-in electricity. The MCF rubber has 4-g TiO\({}_{2}\), 6-g Ni, 4.5-g MF and 9-g NR-latex. At first, the change in the photocurrent density and the built-in current density by elongation is larger with magnetic clusters than without. This is due to the fabrication of the hetero-junction structure. At a constant elongation rate, the positive photocurrent density is decreased together with the negative built-in current density by increasing the compression. This tendency can be understood by considering the absolute values. These results are due to the collapse of the hetero-junction structure due to elongation and compression. On the other hand, at a range of less than about 0.2 of the elongation rate, the MCF rubber is in the inner linear elastic region. In this region, changes in the photocurrent density and built-in current density by elongation are larger than at the plastic region. This is because the hetero-junction structure can be broken up more easily due to elongation and compression at the plastic state than in the linear elastic region. In particular, at the linear elastic region the photocurrent density and built-in current density have peak values; i.e., they are increased once. These are the typical characteristics of the MCF rubber solar cell. We can utilize this tendency in engineering applications to obtain higher efficiency solar cells by elongating the MCF rubber in the inner linear elastic region. Incidentally, this characteristic can also be observed in Figures 11 and 12. Thirdly, we investigated the effect of tension and compression on the MCF rubber solar cell. The change of the built-in electricity and photoelectricity by compression and tension are shown in Figures 13 and 14, respectively. Here the MCF rubber had 3-g TiO\({}_{2}\), 6-g Ni, 4.5-g MF and 9-g NR-latex.The built-in electricity and photoelectricity decreased for larger compression. The maximum compressive strain range is smaller than that in the case of tension because the thickness of the compressed rubber is small, such as 1-mm order. Therefore, the deformation of the compression is in the inner linear elastic region. The built-in electricity and photoelectricity increase once and then decreased as the tension was increased. There exist peaks in the inner linear elastic region. In the plastic region, the built-in electricity and photoelectricity are minimal. It is a significant engineering application regarding H-Skin installed in a robot, and elastic and flexible solar cell to utilize the typical peaks in the inner linear elastic region because we can obtain larger photoelectricity by tension. Figure 13: _Cont_. Regarding tension, the MCF rubber has linear elastic and plastic regions as shown in Figures 11, 12 and 14 during our used tensile condition.