The Science Bit

 

Learn more about how solar PV Panels work?

 

Solar photovoltaic (Solar PV) panels: the science bit

The term "photovoltaic" is derived from the Greek φῶς (phōs) meaning "light", and "voltaic", meaning electric. “Voltaic” comes from the Italian physicist Volta, after whom a unit of electro-motive force, the volt, is named.

 

Cell types

The cells that make up the solar PV panels we see on our roofs are made up of a variery of different types of material. The most important material in the crystalline solar cells is silicon. The PV cells are manufactured by over 100 companies worldwide, and provide the commercially-used cells found in the monocrystalline and polycrystalline panels. These two types of solar panels account for around 95% of the solar modules that are sold throughout the world.

 

Monocrystalline (single crystal) silicon PV cells

The Czochralski process has become the established way to produce single crystal silicon. This process allows the crystal to grow into a cylindrical monocrystal, up to 30cm in diameter and a few metres long. The cylindrical monocrystals are then cut to form either semi-round or square bars. These are cut into what are known as “wafers” – thin slices with a thickness of about 0.3mm.

 

 

 

 

 

 

 

 

 

The efficiency of these PV cells is 13 – 17%. These cells are more efficient than polycrystalline PV cells which are 11 – 15% efficient. However, monocystalline PV cells tend to be more costly to produce as generally require more time and energy.

 

Polycrystalline silicon PV cells

To produce polycrystalline Solar PV cells, silicon granulate is melted into a quartz crucible. It is then cast into the shape of a cube, called directed solidification. The purpose of this process is to form large numbers of the largest homogenous silicon crystal. Large silicon blocks, or ingots, are created as a result of the cube or block casting of the material. The ingots are sawn into bars, and then into wafers which are approximately 0.3mm thick. They are cleaned and doped in phosphorous and the anti-reflective coating is applied. It is this coating which gives the cells its characteristic blue colour.