Souichi Sakai

A new solar cell roofing tile

Abstract A new solar cell roofing tile combining a building material (a glass Japanes-style roof tile) and an amorphous silicon (a-Si) solar cell has been developed. It was made possible by developing new technologies for uniformly fabricating a-Si film on complex curved surfaces such as Japanese tiles and for patterning integrated-type solar cells on large-area curved surfaces. The roofing tiles were installed on a model house and are presently undergoing exposure tests. Their performance as solar cells and as building materials has been satisfactory over the past 2 years.

Recent progress in a-Si solar cells

As concern regarding global environmental problems such as the greenhouse effect and acid rain has increased, so too has the demand for commercially viable solar cells as a clean energy source. Interest in amorphous silicon (a-Si) solar cells has been particulary high, due to their low cost. Technological developments in the field of a-Si solar cells are discussed from the viewpoints of fabrication process, materials, and cell structures. Various applications and systems that take advantage of the a-Si solar cell are then introduced. Finally, future prospects are mentioned.

Integrated type multi-bandgap a-Si solar cells

Abstract A new type of solar cell, called the “integrated type multi-bandgap a-Si solar cell”, in which stacked type solar cells having different bandgaps are integrated on one substrate, was proposed. Materials, design theory and a processing method were investigated. As a narrow bandgap material, a-SiSn:H was first deposited from a glow discharge reaction, and the photovoltaic effect of a-SiSn:H was observed. As a wide bandgap material, a-SiN:B:H deposited from a glow discharge was found to have good properties for use in solar cells. An optimum design theory for this type of a-Si solar cell was established, and it was found to be useful for the fabrication of the integrated structure.

Through-Hole Contact (THC) integrated-type a-Si solar cell submodule by a new laser photo-etching method

Abstract A new laser photo-etching method has been developed for the formation of microscopic holes on a Through-Hole Contact (THC) integrated-type a-Si solar cell which is expected to obtain high output performance. It was confirmed that the insulator film can be removed without causing damage to the TCO (Transparent Conductive Oxide) film during formation of microscopic holes using a laser photo-etching method. A 6/s% increase in the maximum output power of THC solar cells was obtained by optimizing the hole pattern compared with that of conventional solar cells. Based on this technique, a conversion efficiency of 10.55% for 10 cm x 10 cm THC integrated-type a-Si solar cell submodules was achieved.

Laser Photo-etching Method for Maskless Fabrication of a Through-Hole Contact (THC) Amorphous Silicon (a-Si) Solar Cell Submodule

A laser photo-etching method has been developed for the maskless fabrication of microscopic holes on a Through-Hole Contact (THC) integrated-type amorphous silicon (a-Si) solar cell submodule, which is expected to obtain high output performance. Microscopic holes, which were key components of the THC structure, were fabricated very precisely with excellent electrical characteristics by XeCl excimer laser beam with a 308nm wavelength. The conversion efficiency for a 1cm x 1cm THC cell fabricated by this method was 6% higher than that of a 1cm x 1cm conventional cell.