Scientists Achieve Highest Efficiency Using Flexible Cells

               

‘Zero-energy’ buildings – which generate as much power as they consume – are now closer to reality, as scientists have achieved the highest efficiency ever using flexible, non-toxic solar cells that are cheaper to make. Until now, the promise of such buildings have been held back by two hundreds: the cost of the thin-film solar cells (used in facades, roofs and windows), and the fact that they are made from scarce, and highly toxic, materials.

                Researchers at the University of New South Wales in Australia achieved the highest efficiency rating for a full sized thin film technology, known as CZTS. The US National Renewable Energy Laboratory (NREL) has confirmed this world-leading 7.6% efficiency in a one square centimeter area CZTS cell.

                Unlike its thin film competitors, CZTS cells are made from abundant materials, such as copper, zinc, tin and sulphur. CZTS has none of the toxicity problems of its two thin-film rivals, known as CdTe (Cadmium-telluride) and CIGS (copper-indium-gallium-selenide). Cadmium and selenium are toxic at even tiny doses, while tellurium and indium are extremely rare.

                “In addition to its elements being more commonplace and environmentally benign, we’re interested in these higher bandgap CZTS cells for two reasons,” said Martin Green, professor at UNSW. “They can be deposited directly onto materials as thin layers 50 times thinner than a human hair, so there’s no need to manufacture silicon ‘wafer’ cells and interconnect them separately,” he said. “They also respond better than silicon to blue wavelength of light, and can be stacked as a thin film on top of silicon cells to ultimately improve the overall performance.”