Amorphous silicon (a-Si)

Used mostly in consumer electronic products, which require lower power output and cost of production, amorphous silicon has been the dominant thin – film PV material since it was first discovered in 1974. Amorphous silicon is a non-crystalline form of silicon, i. e. its silicon atoms are disordered in structure. A significant advantage of a-Si is its high light absorptivity, about 40 times higher than that of single-crystal silicon. Therefore only a thin layer of a-Si is sufficient for making PV cells (about 1 micrometre thick as compared to 200 or more micrometres thick for crystalline silicon cells). Also, a-Si can be deposited on various low-cost substrates, including steel, glass and plastic, and the manufacturing process requires lower temperatures and thus less energy. So the total material costs and manufacturing costs are lower per unit area as compared to those of crystalline silicon cells.

Despite the promising economic advantages, a-Si still has two major roadblocks to overcome. One is the low cell energy conversion efficiency, ranging between 59 per cent, and the other is the outdoor reliability problem in which the efficiency degrades within a few months of exposure to sunlight, losing about 10-15 per cent.