There are various technolgies at different levels of development that is currently in the works in the industry. However, the most prevalent technolgies are listed below.
Monocrystalline – These are made from cells created by cutting thin slices from single crystal silicon block and are higher in efficiency, but also higher in cost per watt. They are easy to spot because they have a smooth even color, usually black.
Polycrystalline – These are made from cells created by cutting thin slices from polycrystal silicon block and are slightly lower in efficiency, but also lower in cost per watt. Polycrystalline silicon is the “chicken nugget” of silicon, made by combining many individual crystals. They are easy to spot because they have an uneven color, usually blue.
Thin film – These are made by depositing a thin layer of very finely powdered silicon (amorphous silicon) or other photovoltaic material, on a substrate. These are much lower in efficiency that crystalline cells, and somewhat cheaper per watt. They are a good choice for large ground mounted utility scale solar arrays where real estate is plentiful. Their low efficiency makes them undesirable for commercial and residential applications because they consume a large amount of roof space compared to mono or poly modules.