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Research paper−194−Synthesiology - English edition Vol.14 No.4 pp.194-201 (Mar. 2012) silicon solar cell is already being mass-produced in Japan, and is diffusing gradually. It is known that the thin-film silicon does not have high photoabsorption coefficient, and the photoabsorption layer cannot be thickened to suppress the decreased performance due to light irradiation. Therefore, to increase efficiency, it is important to find some way of confining the light in the photoabsorption layer. In general thin-film silicon solar cells, the sunlight is utilized efficiently by using the texture formed on the transparent conductive oxide surface for confinement. For example, in the superstrate thin-film silicon solar cell, where the layers are formed from the front side in the order of transparent conductive oxide, p-type silicon doped layer, i-type silicon photoabsorption layer, n-type silicon doped layer, transparent conductive oxide, and back-side metal electrode, the light is irradiated from the glass substrate side as shown in Fig. 1. Therefore, to achieve increased efficiency, the texture is formed on the transparent conductive oxide surface in the front side to scatter the light and confine it to the photoabsorption layer.Asahi-U manufactured by Asahi Glass Co., Ltd. is a glass substrate on which fluorine doped tin oxide (FTO) transparent electrode is formed, and it is known that the FTO surface with texture optimal for amorphous silicon solar cells can be obtained. In Asahi-U, substrate temperature of about 500 ºC is necessary in the coating process for FTO to form the optimal texture. However, there is no general-use polymer base material with heat resistance of 500 ºC, and higher performance of the flexible thin-film silicon solar cells cannot be achieved by using the same method as in the glass substrate.1 Objectives for the development of flexible solar cellsRecently, the market for photovoltaics is expanding dramatically, and the growth rate is kept at about 40~50 % compared to the previous year. The annual world production volume surpassed 23 GW in 2010. This figure is equivalent to 23 nuclear power plants at peak power. The market is expected to grow steadily, and the annual production volume will reach at least 100 GW by 2030. For the diffusion and expansion of photovoltaics, the lowering of installation cost through weight reduction and the expansion of installation space are important. Since cover glass is used for the light-receiving surface in ordinary solar cell panels, in many cases, the panels cannot be installed on roofs with low withstand load, and the installation may incur considerable cost due to the additional reinforcement of the roof. On the other hand, the flexible solar cells using polymer or metal sheet as base material do not use glass, and weight reduction to about a fraction or 1/10 of the conventional solar cell panel may be possible. This also contributes to increasing the installable space. Other advantages of the flexible solar cell include: it can be applied to curved surfaces, will not break like glass and therefore is safe, has excellent productivity since the roll-to-roll process can be used in manufacturing, and it is easy to transport and store. 2 Strategy and scenario for the development of flexible solar cellsOf the various flexible solar cells, the flexible thin-film - Management of “Flexible Solar Cell Substrates Consortium” and its achievements-Elemental technological challenges required for the development of flexible solar cells have been clarified and a consortium system to solve the problems has been established based on industry-academia-government collaboration. The technology to form texture on polymer base materials indispensable for high efficiency has been developed, and we have succeeded in preparation of thin-film silicon solar cells on polymer base materials whose efficiency is comparable with that of cells prepared on glass substrates. The stage has already moved from research within the consortium to practical realization research in individual enterprises. Establishment process, management policy, patent strategy and training of young researchers of the consortium are described in this paper. Development of high efficiency flexible solar cells Keywords : Flexible thin-film solar cells, consortium study, polymer base materials, texture, training of young researchers [Translation from Synthesiology, Vol.4, No.4, p.193-199 (2011)]Atsushi MasudaResearch Center for Photovoltaic Technologies, AIST 807-1 Shuku-machi, Tosu 841-0052, Japan E-mail : Original manuscript received January 31, 2011, Revisions received September 1, 2011, Accepted September 1, 2011

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