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.
The overall efficiency of this new type of solar cell was 7.1–7.9% (under simulated solar light), which is comparable to that of amorphous silicon solar cells .
The best open-circuit voltages in substrate solar cells are achieved using a boron-doped silicon film . This material is generally referred to as microcrystalline, although extensive characterization of the type presented in Figure 12.13 suggests this p-layer may also be dominated by an amorphous phase.
It is worth noting that these = conditions also apply to photoconductivity measurements that are made on isolated films of a particular material. The asymmetry in the drift of electrons and holes explains why amorphous sili-con–based pin solar cells are more efficient when illuminated through their p-layers.
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.