A joint project between industry and academics funded by the National Science Council has developed new techniques to improve the manufacturing process of GaAs (gallium arsenide) solar cells, which could cut costs by approximately half.
The deputy director of the division of engineering and applied science at the council, Yuen Cheong-wing (阮昌榮), told a press conference yesterday that the project started in December 2009.
Some characteristics of solar cells that counted against them were their high production costs, as well as the energy spent and carbon dioxide emissions involved in their production.
Producing highly efficient, low-cost solar cells in a way that minimizes material waste and carbon dioxide emissions were the objectives of the program, the council said.
Project convener Horng Ray-hua (洪瑞華), a professor at the Graduate Institute of Precision Engineering at National Chung Hsing University, said that in contrast with silicon wafer solar cells or thin-film solar cells, the III-V multi-junction solar cells (GaAs solar cells) showed very high conversion efficiency, at more than 40 percent.
However, because of the relatively expensive cost of the III-V multi-junction solar cell, it is mainly used in artificial satellites or power plants, Horng said. He added that the GaAs substrate was necessary for epitaxial growth — the deposition of a crystalline overlayer on a crystalline substrate — of the cell.
However, the GaAs substrate is expensive and prone to overheating when the cell is functioning, Horng said.
The project’s key achievement was developing a method to separate the GaAs substrate and the crystalline overlayer after the epitaxy process has been completed and the substrate replaced with a copper substrate, which is less expensive and has high thermal capacity.
By enabling the replacement of GaAs substrate, the epitaxial growth time can be shortened, a heat-dissipation mirror can be added and the original GaAs substrate can be reused, cutting total production costs.
The project has applied for five patents and the technology has been transferred to two companies that participated in the collaboration project, Horng said.