Researchers at Northwestern University just unveiled a new solar cell that can be manufactured for less money using fewer harmful elements. Inorganic chemist Mercouri G. Kanatzidis and Robert P. H. Chang collaborated to create a perovskite crystal solar panel that replaces harmful lead with tin – a less expensive and more environmentally friendly material.
Over the past several years, chemists and engineers have identified the pervoskite crystal structure as the next big trend in PV science. Lured by the promise that the compound first discovered in Russia back in 1839 could be both efficient and cheap for cell production, researchers across the globe greatly improved electrical output from their new designs in the last couple of years. The organometal trihalides being tapped for PV research could prove to be a less expensive alternative to silicon cells and be made through basic chemical methods. Instead of factories that require top of the line equipment and sterile environments for cell manufacture, PV devices could be rolled out with simple lab equipment.
Lead Perovskites were able to achieve conversion rates of 15 percent, and the Northwestern team expects tin to soon surpass that mark. Their cell currently sits at six percent, and can absorb a majority of the light spectrum. Each tin cell is made up of five stacked layers. The first is an electrically conducting gas that absorbs light and acts with the second layer of titanium dioxide to create an electrical contact. A hole transport layer is placed below, and the tin Perovskite sits underneath this layer. The backing of the cell is made of gold, and serves as a contact electrode. The whole sandwich is only one to two microns thick.
While the use of tin is less hazardous than poisonous lead, manufacturers must be wary of where they source the material. Much of the metals used in electronics, including the tin and gold found in the cells, are mined from conflict areas in regions like East Africa that have seen social strife result from the hunger for natural resources. As technology advances, businesses and governments will have to consider the wider implications of renewable energy.