Researchers in Toronto have developed a new chemical reaction that will allow for lower cost and higher efficiency perovskite solar cells. This alternative solar technology could lead to low-cost, printable solar panels capable of turning nearly any surface into a power generator. However, creating the electron-selective layer (ESL) of a solar cell, which acts as a bridge between the sun-catching crystals and electrical circuits, has previously relied on high temperatures of above 500 degrees Celsius (932 F), meaning they are too hot to put on top of a sheet of flexible plastic or on a fully fabricated silicon cell.

The new process developed at the University of Toronto allows for the low-temperature creation of an ESL, clearing this major hurdle for perovskite solar cell production. The new reaction enables an ESL to be grown already on top of an electrode in a solution, ensuring temperatures stay below 150 degrees Celsius (302 F) and below the melting point of many plastics.

Professor Ted Sargent (ECE), an expert in emerging solar technologies and the Canada Research Chair in Nanotechnology and senior author on the paper says: “Perovskite solar cells can enable us to use techniques already established in the printing industry to produce solar cells at very low cost. Potentially, perovskites and silicon cells can be married to improve efficiency further, but only with advances in low-temperature processes.”

The University of Toronto’s Sargent Group is a leading researcher in perovskites, a new form of solar cell that doesn’t require the intensive processing, high heat and hazardous solvents involved with the production of traditional silicon-based solar cells. The Canadian solar energy market is growing rapidly, and Toronto was host to the Solar Canada Conference & Exposition in December 2016, representing the entire industry, from researchers to engineers, utilities,to government. Toronto is increasingly recognised as a hub for developing innovative clean tech solutions, including solar, wind and water energy. The University of Toronto itself is home to an Institute for Sustainable Energy, while its Impact Center’s CleanTech Cluster connects industries, academic institutions, government, and related organisations to spur the development of technologies that contribute to clean air, water, soil, and better cities.

Team leader Dr. Hairen Tan says the newly constructed solar cells are also more efficient, as the particles that make up the ESL have been coated with chlorine atoms to better bind it to the perovskite crystal layer. The subsequent efficiency of 20.1 per cent “is the best ever reported for low-temperature processing techniques,” says Tan, noting that cells made using high-temperature methods are only slightly more efficient, at 22.1 per cent, with the best silicon cells only reaching 26.3 per cent. Tan claims these perovskite solar cells are also more stable, retaining more than 90 per cent of their efficiency even after 500 hours of use.

By keeping perovskite production temperatures low, myriad new applications arise, from smartphone covers that provide charging capabilities to solar-active tinted windows that offset building energy use. Tan also suggests teaming up with traditional cells for even greater efficiency.

“With our low-temperature process, we could coat our perovskite cells directly on top of silicon without damaging the underlying material. If a hybrid perovskite-silicon cell can push the efficiency up to 30 per cent or higher, it makes solar power a much better economic proposition.”


(via University of Toronto, New Atlas)

Featured image: Dr Hairen Tan and his colleagues in Professor Ted Sargent’s lab have removed a key barrier to the manufacture of low-cost perovskite solar cells. (Photo: Kevin Soobrian)