The film properties and solar cell performance of amorphous SiGe:H (a-SiGe:H) samples have been systematically investigated, using constant optical gap and various compositions of hydrogen and germanium. It was found that the hydrogen content and bonding configurations play important roles in determining both the initial properties and stability. The optimum compositions were clarified for the minimum Urbach tail characteristic energy and defect density in the as-deposited film, and for the maximum conversion efficiency of the solar cells. The stability of a-SiGe single and a-Si/a-SiGe tandem solar cells becomes higher as the hydrogen content of the photovoltaic layer becomes lower. As a result, the optimum composition after light soaking shifts to the region of lower hydrogen content. Applying the above findings to the design of devices, the highest stabilized conversion efficiencies of 3.3% (initial 3.7%) under red light (λ>650 nm) for an a-SiGe single-junction solar cell and 10.6% (initial 11.6%) for an a-Si/a-SiGe tandem solar cell have been achieved (area: 1 cm2).

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High-quality p-type a SiC films can be fabricated by using a new type of doping gas, B(CH3)3, instead of B2H6 in a photo-CVD method and a glow discharge method. The photoconductivity and doping efficiency of a-SiC films fabricated by the photo-CVD method are improved by using B(CH3)3. A reduction of tail state density and an increase in photoluminescence are also observed. Furthermore, a bandgap narrowing in highly B-doped a-SiC films fabricated by the glow discharge method can be prevented by using B(CH3)3. A conversion efficiency of 10.0% (total area efficiency of 9.02%) is obtained for a 100 cm2 integrated-type a-Si solar cell whose p-layer was fabricated by the glow discharge method with B(CH3)3.

PACS. 36.20 -Macromolecules and polymer molecules. PACS. 05.50 -Lattice theory and statistics; Ising problems. PACS. 64.60 -General studies of phase transitions.Abstract. -Models of a directed polymer chain are studied in the presence of disorder in two and three dimensions, which describe adsorption-desorption transitions due to an attracting substrate. In particular, the free energy and the scaling behavior of the monomer concentration profile in the vicinity of the transition are calculated using a grand canonical ensemble. The scaling form differs from that found in the case of no disorder.