Discovery opens up highly efficient solar panels

A promising type of perovskites, or human-made crystals that can convert sunlight into electricity, could for the first time be stabilized. The new findings pave the way to solar panels that are easy to make and highly efficient.

Perovskites are semiconductor materials that show particular promise in harvesting solar energy. Most solar cells are made with silicon crystals, but perovskite-based devices offer higher conversion efficiencies than silicon.

The problem is that some of the most promising perovskites, including caesium lead triiodide (CsPbI3), are very unstable at room temperature. Now, the material could for the first time be stabilized, thanks to the findings of a study led by KU Leuven.

For the crystals to absorb sunlight efficiently and turn it into electricity, they should be in a black, perovskite state – and stay that way, explains a statement.

“Silicon forms a very strong, rigid crystal. If you press on it, it won’t change its shape. On the other hand, perovskites are much softer and more malleable,” said Dr Julian Steele of the KU Leuven Centre for Membrane Separations, Adsorption, Catalysis, and Spectroscopy for Sustainable Solutions (cMACS). “We can stabilize them under various lab conditions, but at room temperature, the black perovskite atoms really want to reshuffle, change structure, and ultimately turn the crystal yellow.”

Together with an international team of scientists, Steele discovered that by binding a thin film of perovskite solar cells to a sheet of glass, the cells can obtain and maintain their desired black state, according to the statement.

The thin film is heated to a temperature of 330 degrees Celsius, causing the perovskites to expand and adhere to the glass. After heating, the film is rapidly cooled down to room temperature. This process fixates the atoms in the crystals, restricting their movement, so that they stay in the desired black form.

According to Steele, perovskites are attractive in terms of performance and price, but “their stability is still a major issue”. He concluded: “Since the entry level for processing perovskite-based solar cells is relatively low, they can be very beneficial for people in developing countries operating in a more limited infrastructure.” Additionally, perovskites can be used in LEDs, photoelectric sensors, transistors and x-ray detectors.

Photo credit: Steve Rainwater/ CC BY-SA 2.0

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