Researchers at the University of California, Los Angeles (UCLA) recently found adding neodymium ions directly to halide perovskite, instead of adding protective layers, leads to higher efficiency and durability for perovskite solar cells, paving the way for their mass production in near future.
While the human-made halide perovskites—molecules forming a repeating grid of cubes—are cheaper to produce using less expensive materials than silicon, using less energy and simpler manufacturing process, the problem emerges when the material breaks down with exposure to light and heat. Negatively charged ions are then seen to pop out of the perovskite, damaging the crystal structure and diminishing its energy converting properties.
"The ions tend to move through the perovskite like cars on the highway, and that causes the material to break down," explained Postdoctoral Researcher and part of the UCLA research team, Yepin Zhao. "With neodymium, we identified a roadblock to slow down the traffic and protect the material."
To deal with this 'stumbling block' UCLA team augmented the perovskite material, adding electrically charged atoms or ions of a metal called neodymium directly to perovskite.
Adding 8 neodymium ions for every 10,000 molecules of perovskite, led to the augmented solar cell working for over 1,000 hours under continuous light and at maximum power while retaining 93% of its power conversion efficiency.
In contrast, a solar cell with standard perovskite lost half of its efficiency after 300 hours under same conditions, they add.
Another test figured neodymium perovskite cell under continuous light without any external charge retaining 84% of its efficiency after over 2,000 hours, but a standard perovskite retained none of the efficiency after the same time period.
Both the cells were also heated to about 180º F. While augmented perovskite still had 86% of its efficiency after over 2,000 hours, standard perovskite cell lost all of its ability to convert light into electricity.
"Perovskite will be a game changer because it can be mass produced in a way silicon cannot, and we've identified an additive that will make the material better," said the Carol and Lawrence E. Tannas, Jr. Professor of Engineering at the UCLA Samueli School of Engineering and a member of the California NanoSystems Institute at UCLA, Yang Yang.
The team used neodymium as its ions are 'just the right size to nestle within a cubic perovskite crystal' and carry 3 positive charges to hold negatively charged ions in place. This metal is commonly used in microphones, speakers, lasers and decorative glass.
According to Yang, their research could help perovskite solar cells reach the market within next 2 years to 3 years. The work was published in Nature Materials recently.
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