There is good news that an economical manufacturing method for producing low-cost solar cells is coming up.

This follows researchers making strides in overcoming the hurdle of the temperature gradient in developing a low-temperature production process.

Thanks to researchers at the University of Toronto, the making of perovskite solar cells is looking easy in sharp contrast to the costly development of silicon solar cells. Hairen Tan of the University's Faculty of Applied Science & Engineering and the team successfully crossed the hurdle of making low-cost solar devices called perovskite solar cells.

The new method offers cost advantage plus a prospect of printing solar cells just like newspapers with grand economies of scale.

"Economies of scale have greatly reduced the cost of silicon manufacturing," said Ted Sargent, an expert in emerging solar technologies and the Canada Research Chair in Nanotechnology.

Silicon vs Perovskite Solar Cells

Silicon solar cells are made of crystalline slices of silicon. To make these, complex processes are involved including acute processing methods to attain high purity levels and energy-intensive temperature escalation methods to reach 1,000 degrees Celsius. It also involves hazardous solvents of high volumes.

Perovskite solar cells, unlike silicon cells, need only simple techniques such as dip coating, spin coating, thermal evaporation, and vacuum-led crystallization.

The findings have been published in the journal Science.

Printing Industry Techniques

Sargent said perovskite solar cells allow the use of established techniques in the printing industry for making solar cells economically. The expert said a marriage of perovskites and silicon cells will be ideal to boost efficiency further, and that will happen when further strides are made in processes involving low temperatures.

Thanks to perovskite's composition of low-cost, light-sensitive materials, mixing them to a liquid form as a "solar ink" is easy. That can be printed on glass, plastic, and other materials using the inkjet method. Unlike silicon, perovskite solar cells are made with tiny crystals that are 1,000 times smaller than the width of a human hair.

ESL Challenge Addressed

So far the constraint in developing perovskite solar cells had been the difficulty of making a good electron-selective layer. The ESL is where electrons excited by solar energy are extracted from crystals. After extraction the electrons flow through a circuit.

Tan said that in making ESLs, the best materials are in powder form and need baking at high temperatures beyond 500 degrees Celsius.

To solve the ESL problem, Tan and team developed a reaction in which an ESL made of nanoparticles in solution is allowed to grow on an electrode. Though the process also demands heat up, the temperature doesn't exceed 150 degrees Celsius, which is remarkably lower than the melting point of many plastic materials.

Adding a layer of chlorine atoms to the nanoparticles lets the particles bind to the perovskite layer, allowing easier electron extraction.

High Efficiency

According to Tan, solar cells manufactured by the new method showed an efficiency of 20 percent that is the best in a technique of lower temperature conditions.

The new method also gave a sustained performance. Perovskite solar cells have the problem of dipping performance after a few hours.

Tan said the real gain lies in a hybrid perovskite-silicon cell that can an increase efficiency to up to 30 percent. If this is developed, solar power would be a hugely economic proposition.

Tan also mentioned that the cells retained 90 percent of their efficiency after 500 hours of use. Thanks to the success in low-temperature manufacturing, perovskite solar cells are expected to find traction in applications including smartphones and solar-active buildings.

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