Sturdy Solar: Strengthening Perovskite Cells for Sustainable Power
By: Erin Burgard, on Muzhi (Charles) Li’s December 2023 publication in Energy Advances
“Sturdy solar: strengthening perovskite cells for sustainable power”
Around the world, rooftop solar panels traditionally use silicon as conductive material to convert sunshine into electric power. However, silicon solar panels have drawbacks such as limited efficiency and complex manufacturing processes.
To overcome silicon’s limits, scientists are investigating the use of a material called perovskite for the solar panels of the future.
To achieve usable perovskite solar cells, also referred to as PSCs, Muzhi “Charles” Li, an electrical engineering doctoral student at Arizona State University, led an investigation into the effects of fracture energy on the construction of perovskite solar panels.
Fracture energy is the amount of force needed to rip apart an object until it breaks, such as pulling apart the wishbone from a Thanksgiving turkey. Instead of greasing up his hands with turkey drippings and pulling apart a wishbone, Li’s testing consisted of using a machine that gripped opposite ends of solar cell material to pull the sample apart until it cracked in half.
Using the data from the experiments, Li aims to make a durable PSC. Through the project, his collaborators from Jerusalem, Spain, Michigan, Colorado and Texas sent him solar cell samples to analyze.
“It is definitely exciting when I receive a package full of samples, ” Li says. “It’s really like a box of chocolates in Forrest Gump!”
Together, the global team discovered helpful guidelines on PSC construction.
The right criteria for PSC manufacturing
A PSC can be thought of as a layer cake. Protective glass, like frosting, serves as the outer layer, and the perovskite material and various other thin films that encourage the electricity to flow are similar to inner cake layers.
The perovskite layer itself is just 500 nanometers thick. In contrast, a sheet of office paper is 100,000 nanometers thick.
When designing a perovskite solar cell, a scientist can choose either 2D or 3D perovskite, just as a baker may choose thick or thin strawberry frosting layers. Li advocates for 2D perovskites, which make the panels more flexible.
To strengthen the PSC, Li’s collaborators added a “buffer” layer of tin oxide by a method called atomic layer deposition. This buffer layer is an optimal surface to add the next layer on, which optimizes the strength of chemical bonds and solar panel adhesion.
The stronger the adhesion, the more a PSC can resist being pulled apart, making it more durable.
Picking perovskite over silicon
In addition to perovskite’s potential for replacing silicon as a better solar panel material, perovskite represents an opportunity to boost U.S. solar technology manufacturing.
According to the U.S. Energy Information Administration, about 88% of solar panel shipments to the U.S. in 2022 were imported. The shipments come from facilities equipped to handle silicon’s manufacturing needs.
Silicon is found in earth-abundant silica, which is most commonly mined from sand. Purifying silica to 99.9999% silicon is required to build solar panels, and this process takes multiple factories, tremendous temperatures, dangerous chemicals and exceptionally clean and controlled facilities.
Perovskite is easier and costs less to manufacture, as it has “roll-to-roll” compatibility, meaning each step in the manufacturing process can be completed on a conveyor belt.
Making the PSC recipe public
Unlike a family recipe for apple pie, the PSC recipe details found in Li’s experiment are not secret.
The recommendations are “takeaways of the paper, but what is more important is that more attention from the perovskite community can be drawn… to the mechanical properties of PSCs, which have been largely overlooked,” Li says.
Previous research has mainly been focused on perovskites’ electronic properties and degradation prevention methods that don’t involve pulling material apart to test it. Li’s project stresses the importance of increasing the fracture energy of a PSC.
“Knowing the fact that I am exploring uncharted territory that can potentially bring benefits to the perovskite PV and accelerate the commercial viability of the PSCs gives me great passion and enthusiasm to continue what I’m doing,” Li concludes.
Scientists around the world are working to better understand specific parts of PSCs, and collaboration to combine various facets of understanding will be needed to create panels ready for the public. PSC research aims not only to lower production costs and build American-made products, but to reduce climate change and create a cleaner world through the transition from fossil fuels to renewable energy sources.