Using the power of the sun

Chlorine chemistry purifies the silicium for producing solar cells and panels

Chlorine chemistry is imperative to purifying silicon used to make both solar cells and integrated circuits ('chips'), the foundation of modern computer technology.

Besides powering the growth of crops, solar energy has long been used to dry foods for long-term storage, dry the family laundry, and whiten fabrics. But today's solar energy panels convert sunlight directly into electric energy. These panels become ever more important in providing the electric power we need in today's life. And help save other energy resources.  

At the heart of most solar energy panels is a series of high-purity silicon solar cells. These are small, interconnected energy-generating units. Currently, around 95 percent of all solar cells are produced from the chemical element silicon. Chlorine chemistry is essential to purifying silicon used to make both solar cells and integrated circuits, the foundation of modern computer technology.

Solar cells via chlorine chemistry



Because of its unique internal atomic structure and its ready availability, silicon is widely used for solar cells. One of the elements of the Periodic Table of the Elements, silicon is known as a semiconductor, a substance that conducts electricity when there is a change to its environment. In a solar cell, the energy absorbed from sunlight (or other light sources) causes tiny, negatively charged electrons to be knocked loose from silicon atoms. The electrons flow through the material, thus generating electricity. This phenomenon is known as the photovoltaic effect.

But you need highly purified silicon to manufacture solar cells. Here is where chlorine chemistry comes in. Hydrochloric acid is combined with impure silicon-derived from quartz sand-at 300 °C, to produce the compound trichlorosilane HSiCl₃. Trichlorosilane is then heated to a much higher temperature, 1150 °C, at which point it decomposes. One of the products of its decomposition is very pure silicon. Another is hydrochloric acid, which is recycled back into the process.

Solar Energy Outlook

Among 21st century energy resources, renewable solar energy still is a relatively minor player, but one that is growing in importance. Solar energy panels are becoming common sights across the landscape, powering everything from traffic lights to art installations.

They are ingeniously used to power communications satellites in space and the Mars rovers exploring the Red Planet. Increasingly, they are being installed on the sides of buildings and on rooftops, reducing the demand for more traditional energy sources.

Our ability to produce solar energy more efficiently and more economically over time will depend upon how well we apply the tools of chemistry and physics available to us. So far, chlorine chemistry has proven an essential chemistry in developing solar energy panels.

(Text based on information provided by The Chlorine Chemistry Division of the American Chemistry Council (ACC). Visit our colleagues on  http://chlorine.americanchemistry.com/and learn much more about chlorine chemistry applications)