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The two main ways of generating electricity from the sun are thin film photovoltaic (PV) and various types of crystalline silicon. Thin film PV involves coating a substrate material with one or more semiconductor compounds. These thin films typically consist of amorphous silicon, copper indium gallium selenide, or cadmium telluride. Other thin film PV systems make use of dyes or organic compounds. Each of these materials can essentially use sunlight to create electricity through the photovoltaic process.
Some of the first thin film PV cells were used to power small electronics such as calculators. The technology has been improved since then, and low-cost thin film PV cells may provide electricity at or below the cost of grid power in some circumstances. These solar cells are constructed by depositing a substance that has photovoltaic potential onto a substrate material. Both the substrate and the photovoltaic semiconductor can vary in composition, leading to a wide variety of different thin film cells. The smallest thin film cells are only a few nanometers thick, though others are much thicker, and commercially available cells use more substantial substrate materials.
In addition to the photovoltaic compounds and substrate materials, thin film cells also include anti-reflective and transparent coatings and ohmic contacts. They function similarly to traditional solar cells, as photons from sunlight strike the photovoltaic semiconductor and cause some of the component atoms to lose electrons. Electrons that are freed in this manner tend to move to the ohmic contacts as electricity. Thin film PV cells typically exhibit a low efficiency, though they are also fairly inexpensive to produce. This can allow large installations to generate a considerable amount of electricity.
Thin film PV cells are typically available commercially in long strips. This type of material can be suitable for the installation of solar rooftops. Since the thin film cells are typically less expensive than traditional solar cells, it may be more affordable to cover an entire roof. The lower weight associated with thin film can also create less of a stress load than a similar number of solar panels.
Traditional, bulky solar panels are typically made from crystalline silicon and other similar materials. These solar cells operate on the same basic principles as thin film PV, though on a somewhat different scale. Crystalline silicon technology tends to be more costly than other photovoltaics and has also seen improvements based on research into thin films. In addition to being more expensive, these solar panels can also be more efficient than comparable thin film installations.