IBM recently announced a new combination of chemical elements that have a very strong potential to lower the cost of photovoltaic (PV) energy production. The chemicals used at the level of the absorber layer (see photo) have no environmental restrictions, are readily available worldwide and are low cost. Additionally, the process used to make the cells is less expensive.
Some of the largest solar cell manufacturers around the world currently use materials that are relatively expensive, use chemicals that are restricted for environmental reasons or the source minerals used to make the solar cells have limitations in production or in their known ore reserves. This is the case of Cu(In,Ga)(S,Se)2 or CIGS solar panels (includes Cu-Copper, Indium-In, Gallium-Ga, Sulphur-S and Selenium-Se) and CdTe or cadmium telluride panels (includes Cadmium-Cd and Tellurium-Te). Mineral supply restrictions directly affect the cost of Indium (In) and Tellurium (Te), one of the less abundant solid elements on Earth surface. On the other hand, environmental restrictions of heavy metals affect CdTe cells for their content of Cadmium (Cd) which is highly toxic and carcinogenic. Some of these cells are manufactured by vacuum deposition and produce electricity at commercial efficiency rates that are above 9%.
IBM’s announcement is significant in terms of the materials used, the power efficiency rate achieved and the method to manufacture cells of those types. The process to make the cells uses a liquid coating method that combines Copper, Zinc, Tin, Selenium and Sulphur which are widely available and low in cost. Vacuum manufacturing of solar cells is more expensive than liquid coating. Earlier, research using the same chemical elements produced cells with efficiencies below 6.7%. The solar film produced using this new method and chemistry achieved up to 9.6% efficiency combining these elements as Cu2ZnSn(Se,S)4. Other devices fabricated as part of this research produced electric output at efficiency rates greater than 8%.
Additional gains in performance are already envisioned by refining the process to obtain better packing of the photovoltaic film at the molecular level as well as thinner coating. These incipient results have the potential to reduce the cost of solar cells and produce them at a faster rate, besides other applications in opto-electronics. IBM is not planning to produce solar cells. The technology might be available to solar cell manufacturers through partnership with the company.