What does the author suggest about crystal silicon A.It has long been studied for its terrestrial use. B.It is of little use in solar photovoltaic devices. C.It is so economical that it is widely used in the space program. D.It has been efficiently used in extraterrestrial solar cells.
Although many scientists were aware of the very low cost of amorphous solar cells, they felt that they could never be manufactured with the efficiencies necessary to contribute significantly to the demand for electric power. This was based on a misconception about the feature which determines efficiency. For example, it is not the conductivity of the material in the dark which is relevant, but only the photoconductivity, that is, the conductivity in the presence of sunlight. Already, solar cells with efficiencies well about 6 percent have been developed using amorphous materials, and further research will doubtlessly find even less costly amorphous materials with higher efficiencies.