Masataka Kondo

Properties and structure of a‐SiC:H for high‐efficiency a‐Si solar cell

A series of experimental investigations on optical and optoelectronic properties of methane‐ and ethylene‐based a‐SiC:H films has been made. The chemical bonding structure of two kinds of a‐ SiC:H films has also been explored from infrared (IR) absorption structural analysis. An experimental verification for the wide gap window material in the amorphous silicon solar cell is shown on methane‐ and ethylene‐based a‐SiC:H. The methane‐based a‐SiC:H film shows one or two orders of magnitude larger photoconductivity recovery effect of doping than the ethylene‐ based one. IR absorption analysis shows that the methane‐based a‐SiC:H film is recognized as a rather ideal amorphous SiC alloy as compared with the ethylene‐based one. It has been found through these investigations that the methane‐based a‐SiC:H film is superior to the ethylene‐ based one as a window material. Utilizing the methane‐based a‐SiC:H, an 8% efficiency barrier has been broken through with an a‐SiC:H/a‐Si:H heterojunction structure.

Hydrogenated amorphous silicon carbide as a window material for high efficiency a-Si solar cells

Properties and fabrication technical data on glow discharge produced hydrogenated amorphous silicon carbide have been described. A series of experimental studies of the effects of impurity doping on amorphous silicon carbide has also been carried out. It has been shown from the experiment that hydrogenated amorphous silicon carbide prepared by the plasma decomposition of [SiH4(1−x) + CH4(x)] gas mixture has a good valency electron controllability. Employing the property of the valency controlled a-SiC:H as a wide gap window junction, a-SiC:H/a-Si:H heterojunction solar cells have been fabricated. As a result, we have succeeded in breaking through an 8% efficiency barrier with this new material. A typical performance of a-SiC:H/a-Si:H heterojunction cell is Jsc of 15.21 mA/cm2, Voc of 0.88 V, FF of 60.1% and η of 8.04%.

Spectral Effects of a Single-Junction Amorphous Silicon Solar Cell on Outdoor Performance

The device current–voltage (I–V) parameters of single-junction amorphous Si (a-Si) solar cells in natural sunlight at various locations have been investigated over three years. The effective efficiency was compared among testing locations from the latitude of 12.8 degrees to 43.8 degrees. The effective efficiency was varied periodically and the most advantageous performance was obtained in summer at all locations. The increase of output current dominantly contributed to the excellent performance. The output current of single-junction a-Si modules depended not only on module temperature and the annealing effect but also the seasonal variation of the air mass and the atmospheric conditions, such as turbidity and water vapor at each location. The annual performance ratio to initial efficiency measured under standard test conditions reached 82% in Hamamatsu, Japan.

Window Effects of Hydrogenated Amorphous Silicon Carbide in a p-i-n a-Si Solar Cell

A good valency electron controllability has been found in hydrogenated amorphous silicon carbide prepared by the plasma decomposition of [SiH4 + CH4] gas mixture. Utilizing this a-SiC: H layer as window in an a-SiC: H/a-Si: H heterojunction structure, effects of a-SiC: H on the photovoltaic performance have been investigated. A series of systematic experimental data of photovoltaic performance with parameters of methane fraction, optical gap to window side material and p-layer thickness are presented. Remarkable improvements in both short circuit current density and open circuit voltage have been seen in an a-SiC:H/a-Si: H heterojunction cell. This experimental fact implies that not only a wide gap window effect but also voltage factor due to potential profile steepened with wide dap a-SiC: H contribute to the photovoltaic performance of the a-SiC: H/a-Si: H heterojunction solar cell. It has been shown that a-SiC: H might be a useful new material for the development of low cost high efficiency solar cells.

Characterization of a-SiC: H as a Window Material for p-i-n a-Si Solar Cells

A series of experimental investigations on the characterization of methane based and ethylene based a-SiC: H as a window mateial has been made. Chemical bonding structure of two kinds of a-SiC: H films has also been explored from infra-red absorption structural analysis. An experimental verification for the wide gap window material in the amorphous silicon solar cell is shown on methane based and ethylene based a-SiC: H. The methane based a-SiC: H/a-Si : H heterojunction solar cell shows a larger short-circuit current density than the ethylene based one. IR absorption analysis shows that methane based a-SiC: H film is a rather ideal amorphous SiC alloy as compared with the ethylene based one. It has been found through these investigations that the chemical bonding structure is an important factor for a window material.

8% Efficiency a-SiC:H/a-Si:H Heterojunction Solar Cells

An experimental investigation for the wide gap window material in the amorphous silicon solar cell is shown on methane based and ethylene based a-SiC:H. The methane based a-SiC:H/a-Si:H heterojunction solar cell shows a larger short-circuit current density than the ethylene based one. From IR absorption analysis, methane based a-SiC:H film is recognized a rather ideal amorphous SiC alloy as compared with ethylene based one. It has been found through these investigations that the chemical bonding structure is an important factor for a window material. 8% efficiency barrier has been firstly broken through with this methane based a-SiC:H/a-Si:H heterojunction solar cell.