Preparation of High-Quality a-SiGe:H films with Low Impurity Oncentration by the Hydrogen Dilution Method
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PREPARATION OF HIGH-QUALITY a-SiGe.H FILMS WITH LOW IMPURITY CONCENTRATION BY THE HYDROGEN DILUTION METHOD KATSUNOBU SAYAMA, HISAO HAKU, HIROSHI DOHJOH, MASAO ISOMURA, NOBORU NAKAMURA, SHINYA TSUDA, YASUO KISHI, SHOUICHI NAKANO AND YUKINORI KUWANO Functional Materials Research Center, SANYO Electric Co., Ltd. 1-18-13 Hashiridani, Hirakata, Osaka 573, Japan ABSTRACT A-SiGe. H film properties with a low impurity concentration were investigated using a super chamber in the range of Ge content of 0% to 36%. These a-SiGe films can maintain a high photosensitivity of about 106 for Ge content up to 13%, which is comparable to high-quality a-Si films. It was found that impurity incorporation deteriorates optoelectronic properties in the range of a small amount of Ge content, and film rigidity in the range of a large amount of Ge content. Using high-quality a-SiGe films with a low impurity concentration in solar cells, the highest conversion efficiency of 3.15% was obtained for an a-SiGe single-junction cell under red light (AM-l.5, 2 100mW/cm light through the optical filter, in which the wavelength of transmitted light is longer than 650nm). A stacked cell of a-Si/a-Si/a-SiGe has a conversion efficiency of 11.9%. INTRODUCTION We have obtained the world's highest total area conversion efficiency of 10.6% for a l0cmXl0cm integrated-type single-junction a-Si solar cell by combining a number of submodule (Fig. 1). This efficiency was achieved advanced techniques, such as: (1) a Reduced interaction high-quality i-layer and a p/i \ a-SiC buffer-layer using a separated Texture \ (B(CH)3) ultra-high vacuum reaction chamber system called the super chamber, (2) a high-quality p-layer of a-SiC doped with B(CH 3 ) 3 , and (3) a highlytextured TCO with a high haze ratio and gentle slope of the grains which can yield a uniform p-layer. Among high-quality buffer layer Super chamber method high-quality i-layer I these, we believe that the improvement in film-quality by the impurity reduction achieved by the super chamber technique is the most 100mW/cm2 100 AM-1.5 crucial. \ Voc[V] 12.64 For further improvement in the z"E conversion efficiency of a-Si solar Isc[mA] 120.7f C cells, a multi-junction cell is F.F. 0.696 required. A-SiGe alloy is remarked 50F as a promising material for the ;7 [9/] 10.6 bottom cell of high-performance multi-junction cells. In this study, the influence of 10 0 5 impurities on optoelectronic and structural properties of a-SiGe Voltage(V) films is discussed. The improvement in the a-SiGe film quality and cell Fig. I Illuminated I-V characteristics performance utilizing the impurity of an integrated-type a-Si reduction is also considered. solar cell submodule
Mat. Res. Soc. Symp. Proc. Vol. 219. ©1991 Materials Research Society
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PREPARATION Typical fabrication conditions of a-SiGe films using the super chamber are shown in Table I . The hydrogen dilution method (H2/GeH 4 >-25) was used. To clarify the influence of impurities, the changes in a-SiGe film properties were investigated by means of intentional ai
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