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Halide perovskites are a family of materials that promise huge gains in power conversion and performance over typical silicon solar cells, but there’s one problem—they’re not very stable.
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A new study from the Hong Kong University of Science and Technology discovered concavities in the film’s crystalline microstructure, which, when eliminated, greatly increases the film’s stability.
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This could help scientists and engineers overcome one the most enduring problems with perovskites and usher in a new era of power-generating solar devices.
Halide perovskites aren’t exactly a household name, but they could completely transform renewable energy production around the world.
This family of materials, named for the 19th century Russian mineralogist Lev Perovski, promises big gains over the typical silicon solar cells currently used across the industry, whether in a terrestrial power-generating capacity or by powering spacecraft in orbit. However, this power-generating potential is limited by its instability. According to the U.S.’s Office of Energy Efficiency & Renewable Energy (EERE), perovskites “can decompose when they react with moisture and oxygen or when they spend extended time exposed to light, heat, or applied voltage.” So in order to bring this next-generation solar cell technology to the market, scientists need to figure out a way to make them more reliable.
And that’s exactly where new research from the Hong Kong University of Science and Technology (HKUST) comes in. Published last week in the journal Nature Energy, HKUST scientist Yuanyuan Zhou and his colleagues investigated exactly why metal halide perovskite films degraded over time and if there was a method for improving the stability of the material. During their research, the team discovered a “hidden structure” of surface concavities on individual crystal grains, which contributed to the film’s less-than-stellar stability. By eliminating those concavities, Yuanyuan and his team created perovskite films that showed impressive stability gains over previous films.
“By unveiling the grain surface concavities, understanding their effects, and leveraging chemical engineering to tailor their geometry,” Zhou, a co-author of the study, said in a press statement, “we are pioneering a new way of making perovskite solar cells with efficiency and stability toward their limits. We were very intrigued by the surface concavities of perovskite grains when we were using atomic force microscopy to examine the structural details of perovskite films. These concavities are usually buried underneath the film bottom and easily be overlooked.”
To discover these concavities, the researchers analyzed the films and discovered that this “hidden structure” essentially compromised the physical continuity of the film, which is what causes these kinds of materials to degrade quickly intense light and humidity. By using tridecafluorohexane-1-sulfonic acid potassium, a kind of surfactant, the team could manipulate properties of the film, including its strain evolution and ion diffusion, and essentially build a resilient perovskite from scratch. According to the researchers, this new-and-improved material showed major gains in thermal cycling, damp heat, and maximum-power-point tracking tests.
“Microstructure is of vital importance for perovskite solar cells and other optoelectronic devices,” Yalan Zhang, a post-doc researcher at HKUST and study co-author said in a press statement, “and can be more complex than conventional materials owing to the hybrid organic-inorganic characteristics of perovskite materials.”
While this research will help clear one of the largest hurdles to bringing these films to a solar panel near you, scaling up production from these specialized lab devices will be a gargantuan challenge of its own. Regardless of the many years of work ahead, thankfully we now know that weakened stability among perovskites solar cells is a fixable flaw and not an immutable feature.
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