“Economies of scale have greatly diminished the cost of silicon manufacturing,” says lecturer Ted Sargent, an expert in emerging solar technologies and the Canada Research Chair in Nanotechnology. “Perovskite solar cells can allow us to use techniques already established in the printing industry to manufacture solar cells at highly less cost. Potentially, perovskites and silicon cells can be married to enhance efficacy further, but just with advanced in low-temperature procedures.”
Today, virtually all commercial solar cells are prepared from thin slices of crystalline silicone that must be processed to a very high purity. It is an energy-intensive procedure, requiring temperatures higher than 1,000 Degree Celsius and large volumes of hazardous solvents.
In contrast, perovskite solar cells depend on a layer of small crystals, each about 1,000 times smaller than the width of a human hair, made of cost-effective, light-sensitive substances. As the perovskite raw materials can be mixed into a liquid to form a sort of ‘solar ink’, they could be printed onto glass, plastic or other substances employing a simple inkjet printing procedures.
But, till now, there has been a catch, in order to generate electricity; electrons triggered by solar energy must be extracted from the crystals so they can move through a circuit. That extraction occurs in a special layer known as electron selective layer, or ESL. The intricacy of manufacturing a good ESL has been one of core challenges holding back the development of perovskite solar cell devices.
“The most efficient substances for making ESLs begin as a powder and have to be baked at high temperatures, above 500 degrees Celsius,” says Tan. “You cannot put that on top of a layer of flexible plastic or on a fully fabricated silicon cells, it will just melt.”
Tan and his team members introduced a novel chemical reaction that allows them to expand an ESL, made of nanoparticles in solution, directly on top of the electrode. While heat is still needed, the process always stays below 150 Degrees Celsius, much lower than the melting point of numerous plastics.
Keeping cool during the process of manufacturing opens up a world of feasibilities for applications of perovskite solar cells, from smartphone covers that offer charging potentials to solar-active tinted windows that offset building energy use. In the closer term, Tan’s technology could be employed in tandem with traditional solar cells.
“With our low-temperature procedures, we could coat our perovskite cells directly on above silicon without damaging the underlying substance,” says Tan. “If a hybrid perovskite-silicon cell can push the efficacy up to 30 percent or higher, it makes solar power a much better economic proposition.”