Perovskite Solar Cells Push Bounds of Efficiency. Tapping Their Potential Will Be Challenging.

Emerging solar technology holds the promise of cutting energy costs for the U.S. and Europe's transition to renewables, but hurdles remain to widespread adoption.

Solar-cell maker Oxford PV last week said its factory set a record for a commercial-sized solar cell that converted 28.6% of sunlight into electricity, compared with conventional cells offering up to 24%. The same day, Chinese solar giant LONGi said it achieved a 31.8% conversion rate on a research-sized cell. Higher efficiency, measured by how many of the Sun's photons are turned into watts, lowers the cost of generating solar energy.

A spinoff from Oxford University, Oxford PV is among several Western solar companies, including First Solar-acquired Evolar and Saule Technologies, that are pitching advances in efficiency thanks to crystalline minerals called perovskites that can enhance the efficiency of silicon found in today's panels. Oxford PV's technology, which hasn't achieved commercial scale, applies a thin layer of perovskites onto a silicon solar cell before assembling it into a panel. In theory, these so-called tandem cells could reach 43% efficiency versus silicon's limit of 29%.

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"Silicon has reached a wall," Oxford PV Chief Technology Officer Chris Case said. "This perovskite material has done in a decade what silicon has taken two to three decades to do."

At its factory in Brandenburg, Germany, Oxford PV said it is manufacturing cells with an average efficiency of 27% and that it expects efficiency to improve by about 1 percentage point a year. The factory is small, with a 100-megawatt yearly capacity, but can be expanded and Oxford PV has ambitions to increase production in 2024. It is working with panel manufacturers to get industry certifications so it can begin sales next year.

Perovskite solar panels may reach commercialization this decade thanks to an expansion of solar investment spurred by government aid from the U.S. and Europe, solar analysts say. More-efficient panels would ease the world's transition to renewable energy because they need less roof space and land to deliver electricity. By 2030, the globe needs to have more than 5,000 gigawatts of solar capacity to be on track to reach net-zero greenhouse-gas emissions by 2050, up from around 885 gigawatts in 2021, according to the International Energy Agency.

The advances in solar technology are arriving as the U.S. and Europe work to bolster manufacturing capacity to reduce reliance on China, which provides the majority of the world's panels. China dominates more than 80% of the world's manufacturing of solar panels, according to the International Energy Agency. China carved out its position largely because of early government investment, an export-oriented strategy and cheap labor costs.

Perovskite solar panels could fit well into manufacturing that Western nations are building out to expand renewables, solar analysts say, but they caution that new kinds of solar technology have come and gone in the past. Despite perovskite panels having a higher upfront cost to manufacture, they can appeal to customers by delivering a lower price for energy and requiring less space.

"It will be difficult for the U.S. or Europe to compete with Chinese-based companies purely on cost, so a product that offered premium performance at a higher cost might fit in well," said Martin Green, an engineering professor at University of New South Wales.

Still, he said China is working on the same technology and concerns about the durability of perovskite have kept it from taking off. Perovskite manufacturers need to prove panels will last for a 25-year to 30-year lifespan, which is the industry standard. Tests have shown the cells degrade rapidly within months, Green said.

In response, Oxford PV's Case said the company has designed its cells to meet or exceed a 25-year lifetime, proven by studying full-size modules in outdoor environments for more than three years and tests that predict long-term stability. As it awaits certification, he said the company has shared data at industry conferences and is working with the Fraunhofer Institute for Solar Energy Systems ISE to develop testing for the tandem technology because there is no agreed upon industry standard.

"The conversation about degradation is an old one, dating to the early days of perovskite solar technology," Case said.

Perovskite technology is impressive, but more research on its durability and reliability is needed to pave the way for its use in utility-scale solar plants, said Diego Diaz, global head of technology and ventures at renewables giant Iberdrola. Even without perovskite, he said the solar industry is already expected to cut the cost of its generated electricity by 30% between now and 2030, in large part because mainstream silicon is making efficiency gains of about half a percentage point a year.

"Solar is already competitive and will be more so in any case, even if the technology announced fails to reach commercial status," Diaz said.

Write to Dieter Holger at [email protected]

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