Vol.4 No.4 2012

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Research paper : Development of high efficiency flexible solar cells (A. Masuda )−198−Synthesiology - English edition Vol.4 No.4 (2012) transparent conductive oxide manufactured by Asahi Glass, was transferred and then laminated onto the PEN or PI films. Figure 4 shows the photograph of the developed base material. The base film of this material is PEN. The light scattering is reinforced by the transferred texture, and the film appears white to the naked eyes.Figure 5 shows the outline of the fabrication method of the base material. Since the texture became reversed if the Asahi-U or the moth-eye structure was transferred directly, as shown in the scanning electron microscope photograph in Fig. 5, the mold to which the desired structure was initially transferred was used. The UV curable acrylic resin monomer was coated to the mold, and then the general-use PEN or PI film was laminated on top. By irradiating with ultraviolet light after laminating, the monomer changed into polymer. When the film was peeled off from the mold, the polymer material laminated with acrylic resin onto which the texture was transferred was obtained. As shown in the atomic force microscope photograph in Fig. 5, it can be seen that the texture is present on the base material surface. This method can be used not only for the single substrate method shown in Fig. 5, but it has been proven applicable to the roll-to-roll method as shown in Fig. 6, and there seems to be no barrier to mass production.The current-density and voltage characteristics of the amorphous silicon solar cells fabricated on the PI and PEN films are shown in Fig. 7, and the quantum efficiency spectra are shown in Fig. 8. The amorphous silicon solar cell has a substrate structure with the following structure: polymer base material, acrylic resin layer with texture, gallium doped zinc oxide layer, silver back surface electrode layer, gallium doped zinc oxide layer, n-type amorphous silicon doped layer, i-type amorphous silicon photoabsorption layer, p-type amorphous silicon doped layer, indium tin oxide transparent electrode, and silver collector electrode. It is shown in Fig. 7 that sufficient light confinement is obtained on the polymer base material, and the current density increases by using the base material with the texture. From Fig. 7, it also becomes clear that there is Fig. 6 Outline of base material fabrication method by roll-to-roll methodFig. 5 Outline of the base material fabrication by single-substrate method and the microscope photograph of Asahi-U and base material surfacesAsahi-UCoating of UV curable resinBase material surfaceBase material surfaceSecond transferFirst transferPeelingUV curingLaminate filmRollingCoating of UV curable resinUV curable resinTransfer, UV curing, demoldingTextured filmBase materialCoating roleCoating dieUV irradiationRoll moldRubber roleDemoldingTransfer

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