The use of amorphous silicon in the silicon-based solar cells is the most recent and an emerging technology these days. It is a cost-efficient approach and offers the great flexibility. The only disadvantage of amorphous silicon-based solar cells is the reduced efficiency and poor performance.
Amorphous silicon solar cells are normally prepared by glow discharge, sputtering or by evaporation, and because of the methods of preparation, this is a particularly promising solar cell for large scale fabrication.
Amorphous Si solar cells have been produced for electronic calculators, although the energy conversion efficiency is 5 to 7% and is lower than that of crystalline Si solar cells. In the middle of the 1980s, high quality a-Si technology led to the production of a liquid crystal television with a-Si TFT.
While the early deposition work was performed using primarily DC and RF PECVD , Iic-1 -Amorphous Silicon Solar Cells 283 subsequent studies showed that good quality a-Si alloys could be deposited using VHF (~30-110 MHz) and microwave (~2.45 GHz) PECVD [10, 11].
Amorphous silicon solar cells were first introduced commercially by Sanyo in 1980 for use in solar-powered calculators, and shipments increased rapidly to 3.5 MWp by 1985 (representing about 19% of the total PV market that year). Shipments of a-Si PV modules reached ~40 MWp in 2001, but this represented only about 11% of the total PV market.
In 1990, Kishi and co-workers fabricated the world's first flexible amorphous silicon solar cell on a transparent plastic substrate. Although its thickness is only 0.12 mm and bending radius is only 5 mm, the cell had the world's highest calorific value of 275 mW/g at that time.