Improvement in the FF over 0.700 by controlling the interface quality
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1165-M06-06
Improvement in the FF over 0.700 by controlling the interface quality K. Kushiya, Y, Tanaka, H. Hakuma, S. Kijima, T. Aramoto, Y. Fujiwara, Y. Chiba, H. Sugimoto, Y. Kawaguchi and K. Kakegawa Solar Business Center (Atsugi), Showa Shell Sekiyu K.K., 123-1, Shimo-kawairi, Atsugi, Kanagawa, JAPAN, Mail-code 243-0206 Tel: +81-46-245-1750, Fax: +81-46-246-8761 ABSTRACT In this study, pn hetero-interface between Zn(O,S,OH)x buffer and Cu(InGa)(SSe)2 (CIGSS) surface layers is discussed in order to achieve the fill factor (FF) over 0.73 and the circuit efficiency of 16 % on aperture area of over 800 cm2. Two resistances, i.e. shunt (Rsh) and series (Rs) resistances, in the circuits are employed as a yardstick to evaluate the interface quality. It is important to reduce the Rs, because it is mainly correlated to the buffer deposition process. As a much easier and simpler tool to evaluate the Rs, the difference between Voc and optimum-power voltage (Vop) (i.e. Voc-Vop [V/cell]) is applied. We consider that Rs is dependent on the remaining Zn(OH)2 concentration in the Zn(O,S,OH)x buffer deposited by a chemical-bath deposition (CBD) technique. As an approach to make the Rs minimize and the Rsh maximize simultaneously, thinner CBD-Zn(O,S,OH)x buffer layer is deposited by combining with a nondoped ZnO layer deposited by a metal-organic chemical vapor deposition (MOCVD) technique, which is effective to reduce the remaining Zn(OH)2 concentration. Determining the optimized deposition procedure of the stacked buffer layer of CBD-Zn(O,S,OH)x and MOCVD-non-doped ZnO, circuit efficiency of 15.3 % on an aperture area of 856 cm2 has been achieved with the FF of 0.717. INTRODUCTION Showa Shell Solar K.K., a 100 % subsidiary of Showa Shell Sekiyu K.K., is currently operating two plants in Miyazaki city. One is the 20 MW/year plant, which was started up October 2006. Another is the 60 MW/year plant, which was started up November 2008. The first plant is steadily improving both the performance and the production yield. The second one is in a starting-up stage, but gradually increasing the production capacity. Two manufacturing plants will be in full operation by the middle of 2009. This meant that we could transfer our baseline Cu(InGa)(SSe)2(CIS)-based thin-film photovoltaics (PV) technology successfully to the commercialization stage, which was developed under PV-R&D projects entrusted by the New Energy and Industrial Technology Development Organization (NEDO) from FY1993 to FY2005. The transferred baseline technology was the one to enable the average aperture-area module efficiency of 12 % on a 30cmx120cm-sized glass substrate. However, in order to reduce the production cost and improve the competitive ability of our products, twice larger substrate size of 60cmx120cm was employed in the commercialization. All of production know-how, lessons and operational experiences, which were obtained in both the R&D and the first plant, were transferred to the three-times larger second plant combining with our baseline manufacturing tech
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