Photovoltaic solar cells most commonly found in the form of a solar-panel utilise the semiconducting material of crystalline, generating electricity when exposed to sunlight. There are three main types of raw crystalline which are used to produce energy; the efficiency of each depends on the environmental setting. Hot or cold temperatures and whether they are exposed to direct sunlight or that which is diffused.
Polycrystalline or polysilicon consists of many small crystals, producing a metal flake effect, with a light blue mosaic style finish. These are efficient in diffused light and when temperatures are lower. Due to global mass production these tend to be the most cost efficient solar PV option.
In contract to Polycrystalline which consists of many crystals, Monocrystalline cells consist of one single unbroken structure. They are black or dark blue in appearance, efficient in direct sunlight and when temperatures are higher. Due to the darker finish, aesthetically these can be more subtle when reflecting light.
Amorphous silicon is one or more layers of silicon deposited on a substrate. Lower in efficiency but can be manufactured in flexible and thin fabrics. As well as being available in a more flexible material the cells are also efficient in low light conditions; which is what you will find in a pocket calculator. Most commonly used in lightweight applications.