Hurdle to cheap printed solar cells ‘cleared’ by Canadian researchers

Complex crystalline minerals known as perovskites have been a matter of interest in solar cell research for some years, as they have the potential to be far cheaper than cells made from pure silicon. However, although perovskites are efficient at freeing electrons when struck by photons, one barrier to their production has been the difficulty in extracting these freed electrons from the crystal structure so they can flow through a circuit.

Researchers at the University of Toronto (U of T) now claim to have developed a method for achieving this goal. Using chemical reactions to make an electron-selective layer (ESL) in direct contact with perovskite-containing layer, they claim that this method could allow perovskite solar cells to be fabricated by a cheap printing process.

One of the advantages of perovskites is that micro-crystals of the substance can be mixed into an organic ink and printed directly onto glass, plastic or other materials using standard inkjet technology. But the ESL problem has meant that these printed films could not be used as functional cells. "The most effective materials for making ESLs start as a powder and have to be baked at high temperatures, about 500° C," explained Hairen Tan of the department of computing and electrical engineering at U of T, who led the research. "You can't put that on top of a sheet of flexible plastic or on a fully fabricated silicon cell – it will just melt."