What is the difference between monocrystalline, polycrystalline, and thin film solar panels?

Monocrystalline solar panels are panels cut from single slabs of silicon. They are identifiable by their consistent color throughout the panel and are often a dark blue to almost black color. Historically, monocrystalline panels have had the highest efficiency (around 15-17%) because being cut from a single slab of silicon allows a greater level of purity in the silicon, but have also been more expensive for the same reason.

Polycrystalline panels are those created from many different pieces of silicon crystal. Because these panels can be essentially filled in they have historically been cheaper and also had a slightly lower efficiency level (12-14%). These are clearly distinguished between monocrystalline panels by their patches of color, and are also usually lighter blue in color compared to monocrystalline panels.

Thin film panels are panels are purposely made to be thin and flexible for a greater variety of applications. Small layers of semi-conductive material are coated over a more durable material such as metal or plastic and then covered by a transparent weatherproofed layer. Because thin film panels are made of much thinner layers of silicon their efficiency (6-12%) is typically lower than the rigid monocrystalline or polycrystalline panels as the thin layer cannot absorb as much of the light.

An additional type of extremely high-efficiency solar panel (up to 40%), called a multi-junction panel, is also available although typically not used in residential applications. Multi-junction panels work by incorporating different kinds of materials in the panel to capture multiple wavelengths of light that a regular monocrystalline or polycrystalline cell cannot. This effectively breaks up the light collecting process into multiple smaller parts, wasting less of the incoming light in the process. These cells are very expensive and normally only used for special applications.