By finding a new way to manufacture low-cost perovskite solar cells, a team at the University of Toronto believes that making solar cells could someday be as easy and inexpensive as printing a newspaper. The researchers' alternative solar technology supports the development of low-cost, printable solar panels capable of turning nearly any surface into a power generator.

Perovskite solar cells depend on a layer of tiny crystals — each about 1,000 times smaller than the width of a human hair — made of low-cost, light-sensitive materials. The perovskite raw materials can be mixed into a liquid, and the "solar ink" can then be printed onto glass, plastic, or other materials using a simple inkjet process.

Until now, however, solar power had to extract electrons from the crystals to then flow through a circuit. The extraction happens in a special layer: the electron-selective layer, or ESL. The difficulty of manufacturing an ESL has been one of the main challenges holding back the development of perovskite solar cell devices.

Post-doctoral researcher Hairen Tan and his colleagues created a new chemical reaction that enables them to grow an ESL made of nanoparticles in solution, directly on top of the electrode. While heat is still required, the process remains below 150 degrees °C, much lower than the melting point of many plastics.

The new nanoparticles are coated with a layer of chlorine atoms, which binds them to the perovskite layer on top. The strong connection enables efficient extraction of electrons.

The manufacturing process opens up possibilities for applications of perovskite solar cells, from smartphone covers that provide charging capabilities to solar-active tinted windows that offset building energy use. In the nearer term, Tan says his technology could be used together with conventional solar cells.

“With our low-temperature process, we could coat our perovskite cells directly on top of silicon without damaging the underlying material,” said Tan.

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