Solar cells are the semiconductor building blocks that convert light directly into electricity. If you string these small electric generators end to end, you can create a large solar panel that will be able to produce enough electricity to power lights, appliances and even entire households. The key ingredient to this photovoltaic magic is silicon.
Silicon is an element found in great abundance on the surface of the earth. It's mainly in the form of silicon dioxide and is also known as sand. It is the key ingredient used to make the two main types of solar panels: crystalline and amorphous.
Making crystalline solar panels requires a lot of time, energy & material. A cylindrical column of pure silicon (99.99999% pure) is grown in a high-temperature furnace and then cut into very thin wafers. Each disk is 1" to 12" in diameter and is then reheated at high temperatures where phosphorous and boron is doped into the rigid disk.
Once cooled, the thin disks of N-Type and P-Type semiconductors are cleaned with mild acids and textured to create a rough surface. A rough surface has more surface area which increases the solar cell efficiency. The disk is then cut to fit the final product.
Wires are attached to either end of the solar cell to create a chain. As the chain increases in size, the more current it can generate. The chain is then laid in a rigid panel and a layer of glass is placed on top for protection. The transparent glass allows light to pass through yet provides enough structural integrity to withstand outdoor temperatures and rough weather.
Unlike crystalline solar panels, amorphous solar panels are not made up of a chain of solar cells. At very high temperatures, a thin layer of silicon, phosphorous and boron is sprayed onto a backing material. The layer is thinner than a human hair. The backing material can be glass, metal and even plastic to make solar-powered products such as solar glass, solar roof tiles and even flexible solar panel rolls. And entire surface can be coated with this 'spray-on' solar panel. Costly wires are not used nor are expensive silicon wafers needed.
Solar energy from the sun is made of electromagnetic radiation of various wavelengths. Some of these wavelengths can be seen with our human eyes and show up as colors. Others we can not see yet still hit the surface of the earth.
Multi-junction photovoltaic cells are new amorphous solar cells made up of layers of semiconductor material where each thin layer can generate electricity from different wavelengths. Each layer captures a certain wavelength of the sunlight as it passes through the panel. By stacking multiple layers on top of one another, more electricity is generated in the same amount of surface area as one panel.