Reducing “payback time” – that is, the time it takes for a solar panel to produce enough power to offset the energy used in its manufacture – is driving Sue Carter, professor of physics at the University of California, Santa Cruz, to develop cheaper and more efficient solar cells.
Recognising that although conventional silicon crystalline solar cells are used in the majority of solar energy systems worldwide, Professor Carter believes the amount of energy spent in the high-temperature process production of these panels puts thin-film solar cell technology at the front of the pack in terms of potential improvement.
Thin-film solar cells use much less material than silicon cells and offer advantages such as light weight and the potential to deposit them on flexible substrates. But incredibly rare and expensive elements like cadmium telluride (CdTe) are used in their production. Cadmium telluride safety issues have also raised concerns.
Carter’s lab has developed a procedure for making ultrathin solar cells using cheaper processing and only about 10 percent of the material needed to make standard cells.
“We do the processing under normal temperatures and pressures, so it uses a lot less energy than vacuum-based processing,” Carter said. “And we were able to cut the thickness down from three microns to about 360 nanometers and still get good power efficiencies, so the amount of material you need is almost an order of magnitude less.”
Professor Carter’s lab has received a grant from the US National Science Foundation to research using copper-based materials for thin-film solar cells. This work is motivated by concerns about the toxicity of cadmium, lead, and other materials used in thin-film solar cells.
“If we want to scale up solar energy production to terawatt volumes, we need to use more abundant materials,” Carter said.
(Image credit R.R Jones)
