What are thin-film solar cells?

Thin-film solar cells are solar cells in which a very thin layer of light-sensitive semiconductor material, often only a few micrometres thick, is deposited on a substrate. That substrate can be glass, metal foil or plastic. This sets them apart from mainstream crystalline silicon cells, which are made from much thicker slices (wafers) of silicon. Like other photovoltaic cells, they convert sunlight directly into direct current.

Types

• Amorphous silicon (a-Si): the oldest thin-film technology, familiar from pocket calculators. Cheap, but with low efficiency.
• Cadmium telluride (CdTe): widely used in large solar farms. It contains cadmium, so collection and recycling at end of life are important.
• CIGS (copper indium gallium selenide): the most efficient thin-film type, also available as flexible panels.

Pros and cons

Advantages
– Lightweight and sometimes flexible, so suitable for roofs with limited load capacity or curved surfaces.
– An even, often dark appearance without a visible cell pattern.
– Less material per panel.

Disadvantages
– Lower efficiency per square metre than crystalline panels, so you need more roof area for the same yield.
– A smaller range for homes. Domestic roofs almost always get crystalline panels.

Uses in buildings

Thin-film is used mainly where weight, shape or appearance matter more than maximum output per square metre:

• Building-integrated PV (BIPV): solar cells in facade panels, glazing or roofing.
• Lightweight commercial roofs that cannot carry a heavy ballasted panel system.
• Flexible applications, such as curved roofs, caravans and boats.

Practical points

1. Compare output per square metre, not just the price per panel.
2. Check the warranties on power output and product, as with any panel.
3. Have the roof’s load capacity assessed if in doubt, even for lightweight systems.

Related terms

• Photovoltaic
• Concentrated solar power
• Back-up heating for a solar water heater
• Roof covering

Want to learn more about construction terms? Visit our knowledge base at fredsdiyplans.com.