Solar PV capacity is growing rapidly across the United States (and elsewhere). In the last decade alone the market for solar has grown by 24 percent each year, according to the Solar Energy Industries Association (SEIA). Across the US, there’s already 149 gigawatts of solar capacity installed, which could theoretically power 26 million homes. The future seems bright too, as SEIA and Wood Mackenzie predict that the solar market will triple in size in five years, bringing capacity up to 378 gigawatts in 2028. Solar power made up 1.2 trillion watts of electricity produced worldwide in 2022.
Solar energy development and investment is crucial to building a cleaner, more sustainable future, as the technology allows for a great deal of energy to be produced while emitting no planet-harming greenhouse gasses. The technology has come a long way in recent years (and leaps and bounds from its first stages in the 19th century), but efficiency of the average solar panel still stands at about 15-20 percent on average. That means around 80-85 percent of the raw energy beaming down from our favorite star is lost. Not to mention that silicon solar cells, which are the most common deployed photovoltaic tech, have a theoretical limit of around 29 percent efficiency.
Scientists have been trying to solve this problem for years. One team from NREL made a panel with 47 percent efficiency, but unfortunately, the model is a bit too expensive for mainstream use. However, described in two separate papers published in Science on July 6, two different teams of researchers found a way to give silicon solar panels a much needed boost—perovskite.
Perovskite is a mineral that has the same crystal structure as calcium titanium oxide, but can be made up of several different elements for different purposes, according to the University of Washington. They also make for a pretty solid semiconductor for solar panels with a laboratory record efficiency at 25.2 percent.
The two teams paired up perovskite with silicon to make a tandem solar cell. These technologies aren’t necessarily new—the first one was developed in 2009, and a team from Hong Kong was able to bring efficiency up to around 25 percent in 2016. But, now scientists are reaching even higher.
In one study, Xin Yu Chin of Switzerlands’ Ecole Polytechnique Fédérale de Lausanne and team used a perovskite top cell and silicon bottom cell, adding phosphonic acid additives during the processing of the cells. Their cell reached efficiencies of 31 percent.
The other team, led by Helmholtz-Zentrum Berlin für Materialien und Energie’s Silvia Mariotti, used an ionic liquid called piperazinium iodide to enhance their tandem solar cell, achieving an efficiency rate of up to 32.5 percent.
“Overcoming this threshold provides confidence that high-performance, low-cost PVs can be brought to the market,” material science researchers Stefaan de Wolf and Erkan Aydin, who were not involved in the research, wrote in a related perspective article published in Science.
The competition is heating up outside of Europe as well—de Wolf, a professor at King Abdullah University of Science and Technology in Saudi Arabia, claims his team has achieved 33.7 percent efficiency in a yet unpublished tandem cell test run earlier this year. LONGi, a Chinese company that produces a majority of the world’s solar panels, announced their development of a tandem solar panel with an efficiency of 33.5 last month.
As exciting as this all is, it’s still just the very beginning. We need a lot more clean energy to reduce greenhouse gas emissions to keep the planet liveable.
“Overcoming the 30 percent threshold provides confidence that high performance, low-cost PVs can be brought to the market,” De Wolf told the Guardian. “Yet to avert the catastrophic scenarios associated with global warming, the total capacity needs to increase to about 75TW by 2050.”