Amorphous silicon (a-Si)Amorphous silicon (a-Si)AKAAKA

Thin FilmThin Film

Jenny Gould

and

Alec Stall

What is amorphous silicon (a-Si)?What is amorphous silicon (a-Si)?

A semiconductor material only a few micrometers thick, attached to an inexpensive backing such as glass, flexible plastic, or stainless steel.

Amorphous solids, like common glass, are materials in which the atoms are not arranged in any particular order. They do not form crystalline structures at all, and they contain large numbers of structural and

bonding defects.

Pros and ConsPros and Cons

Low cost Amorphous silicon absorbs

solar radiation 40 times more efficiently than does single-crystal silicon, so a film only about 1 micron (one one-millionth of a meter) thick can absorb 90% of the usable solar energy

Can be produced at a lower temperature and can be deposited on low-cost substrates

Amorphous silicon has no crystal structure and is gradually degraded by exposure to light through the Staebler-Wronski Effect.

Combined with some start-up problems with encapsulation and quality control, the poor outdoor performance of a-Si products has, until recently, defined the reputation of thin films.

Cost comparisonCost comparison

Manufacturer Panel Output $/Watt

Kaneka K 58 58 Watts $3.26/w

Sanyo(amorphous and crystalline combined)

HIT 167 167 Watts $6.8/w

UniSolar US 64 64 Watts $6.3/w

Shell Solar ST 40 40 Watts $7.5/w