30-Year Perovskite Solar Cell

An rising class of photo voltaic vitality expertise, made with perovskite semiconductors, has handed the long-sought milestone of a 30-year lifetime. The Princeton Engineering researchers who designed the brand new gadget additionally revealed a brand new technique for testing long-term efficiency, a key hurdle on the street to commercialization. Credit: Photos by Bumper DeJesus

30-year perovskite photo voltaic cells and the brand new method for testing them for the lengthy haul.

Princeton Engineering scientists have developed the primary perovskite photo voltaic cell with a commercially viable lifetime, marking a significant milestone for an rising class of renewable vitality expertise. The analysis workforce initiatives their gadget can carry out above business requirements for round 30 years, excess of the 20 years used as a threshold for viability for photo voltaic cells.

The gadget just isn’t solely extremely sturdy, but it surely additionally meets frequent effectivity requirements. In reality, it’s the first of its form to rival the efficiency of silicon-based cells, which have dominated the market since their introduction in 1954.

Perovskites are semiconductors with a particular crystal construction that makes them properly suited to photo voltaic cell expertise. They may be manufactured at room temperature, utilizing a lot much less vitality than silicon, making them cheaper and extra sustainable to supply. And whereas silicon is stiff and opaque, perovskites may be made versatile and clear, extending solar energy properly past the enduring rectangular panels that populate hillsides and rooftops throughout America.

Toward Commercial Viability of Perovskite Solar Cells

An array of perovskite photo voltaic cell designs sit underneath vibrant gentle at excessive temperatures throughout an accelerated getting older and testing course of developed by Princeton Engineering researchers. The new testing method marks a significant step towards the commercialization of superior photo voltaic cells. Credit: Photo by Bumper DeJesus

But not like silicon, perovskites are notoriously fragile. Early perovskite photo voltaic cells (PSC), created between 2009 and 2012, lasted solely minutes. The projected lifetime of the brand new gadget represents a five-fold enhance over the earlier report, set by a decrease effectivity PSC in 2017. (That gadget operated underneath steady illumination at room temperature for one yr. The new gadget would function for 5 years underneath comparable lab circumstances.)

The Princeton workforce, led by Lynn Loo, the Theodora D. ’78 and William H. Walton III ’74 Professor in Engineering, revealed their new gadget and their new technique for testing such gadgets in a paper printed on June 16, 2022, within the journal Science.

Loo mentioned the record-setting design has highlighted the sturdy potential of PSCs, particularly as a technique to push photo voltaic cell expertise past the bounds of silicon. But she additionally pointed previous the headline outcome to her workforce’s new accelerated getting older method because the work’s deeper significance.

Testing the Lifetime of a Highly-Stable Perovskite

Looking at a extremely steady perovskite photo voltaic cell underneath magnification throughout an accelerated getting older course of that helps researchers forecast the prolonged lifetimes of superior designs. Credit: Photo by Bumper DeJesus

“We might have the record today,” she mentioned, “but someone else is going to come along with a better record tomorrow. The really exciting thing is that we now have a way to test these devices and know how they will perform in the long term.”

Due to perovskites’ well-known frailty, long-term testing hasn’t been a lot of a priority till now. But because the gadgets get higher and last more, testing one design in opposition to one other will turn into essential in rolling out sturdy, consumer-friendly applied sciences.

“This paper is likely going to be a prototype for anyone looking to analyze performance at the intersection of efficiency and stability,” mentioned Joseph Berry, a senior fellow on the National Renewable Energy Laboratory who specializes within the physics of photo voltaic cells and who was not concerned on this examine. “By producing a prototype to study stability, and showing what can be extrapolated [through accelerated testing], it’s doing the work everyone wants to see before we start field testing at scale. It allows you to project in a way that’s really impressive.”

While effectivity has accelerated at a exceptional tempo over the previous decade, Berry mentioned, the steadiness of those gadgets has improved extra slowly. For them to turn into widespread and rolled out by business, testing might want to turn into extra subtle. That’s the place Loo’s accelerated getting older course of is available in.

“These kinds of tests are going to be increasingly important,” Loo mentioned. “You can make the most efficient solar cells, but it won’t matter if they aren’t stable.”

How they received right here

Early in 2020, Loo’s workforce was engaged on varied gadget architectures that will preserve comparatively sturdy effectivity — changing sufficient daylight to electrical energy to make them priceless — and survive the onslaught of warmth, gentle, and humidity that bombard a photo voltaic cell throughout its lifetime.

Xiaoming Zhao, a postdoctoral researcher in Loo’s lab, had been engaged on quite a lot of designs with colleagues. The efforts layered totally different supplies so as to optimize gentle absorption whereas defending essentially the most fragile areas from publicity. They developed an ultra-thin capping layer between two essential elements: the absorbing perovskite layer and a charge-carrying layer made out of cupric salt and different substances. The aim was to maintain the perovskite semiconductor from burning out in a matter of weeks or months, the norm at the moment.

It’s onerous to understand how skinny this capping layer is. Scientists use the time period 2D to explain it, which means two dimensions, as in one thing that has no thickness in any respect. In actuality, it’s merely a number of atoms thick — greater than one million instances smaller than the smallest factor a human eye can see. While the concept of a 2D capping layer isn’t new, it’s nonetheless thought of a promising, rising method. Scientists at NREL have proven that 2D layers can enormously enhance long-haul efficiency, however nobody had developed a tool that pushed perovskites anyplace near the business threshold of a 20-year lifetime.

Zhao and his colleagues went by means of scores of permutations of those designs, shifting minute particulars within the geometry, various the variety of layers, and making an attempt out dozens of fabric mixtures. Each design went into the sunshine field, the place they may irradiate the delicate gadgets in relentless vibrant gentle and measure their drop in efficiency over time.

In the autumn of that yr, as the primary wave of the pandemic subsided and researchers to returned to their labs to are likely to their experiments in rigorously coordinated shifts, Zhao seen one thing odd within the information. One set of the gadgets nonetheless appeared to be working close to its peak effectivity.

“There was basically zero drop after nearly half a year,” he mentioned.

That’s when he realized he wanted a technique to stress take a look at his gadget sooner than his real-time experiment allowed.

“The lifetime we want is about 30 years, but you can’t take 30 years to test your device,” Zhao mentioned. “So we need some way to predict this lifetime within a reasonable timeframe. That’s why this accelerated aging is very important.”

The new testing technique accelerates the getting older course of by illuminating the gadget whereas blasting it with warmth. This course of accelerates what would occur naturally over years of normal publicity. The researchers selected 4 getting older temperatures and measured outcomes throughout these 4 totally different information streams, from the baseline temperature of a typical summer season day to an excessive of 230 levels Fahrenheit, higher than the boiling point of water.

They then extrapolated from the combined data and forecast the device’s performance at room temperature over tens of thousands of hours of continuous illumination. The results showed a device that would perform above 80 percent of its peak efficiency under continuous illumination for at least five years at an average temperature of 95 degrees Fahrenheit. Using standard conversion metrics, Loo said that’s the lab equivalent of 30 years of outdoor operation in an area like Princeton, NJ.

Berry of NREL concurred. “It’s very credible,” he said. “Some people are still going to want to see it play out. But this is much more credible science than a lot of other attempts at forecasting.”

The Michael Jordan of solar cells

Perovskite solar cells were pioneered in 2006, with the first published devices following in 2009. Some of the earliest devices lasted only seconds. Others minutes. In the 2010s the device lifetimes grew to days and weeks and finally months. Then in 2017, a group from Switzerland published a groundbreaking paper on a PSC that lasted for one full year of continuous illumination.

Meanwhile, the efficiency of these devices has skyrocketed over the same period. While the first PSC showed a power-conversion efficiency of less than 4 percent, researchers boosted that metric nearly tenfold in as many years. It was the fastest improvement scientists had seen in any class of renewable-energy technology to date.

So why the push for perovskites? Berry said a combination of recent advances make them uniquely desirable: newly high efficiencies, an extraordinary “tunability” that allows scientists to make highly specific applications, the ability to manufacture them locally with low energy inputs, and now a credible forecast of extended life coupled with a sophisticated aging process to test a wide array of designs.

Loo said it’s not that PSCs will replace silicon devices so much that the new technology will complement the old, making solar panels even cheaper, more efficient, and more durable than they are now, and expanding solar energy into untold new areas of modern life. For example, her group recently demonstrated a completely transparent perovskite film (having different chemistry) that can turn windows into energy-producing devices without changing their appearance. Other groups have found ways to print photovoltaic inks using perovskites, allowing form factors scientists are only now dreaming up.

But the main advantage in the long run, according to both Berry and Loo: Perovskites can be manufactured at room temperature, whereas silicon is forged at around 3000 degrees Fahrenheit. That energy has to come from somewhere, and at the moment that means burning a lot of fossil fuels.

Berry added this: Because scientists can tune perovskite properties easily and broadly, they allow disparate platforms to work smoothly together. That could be key in wedding silicon with emerging platforms such as thin-film and organic photovoltaics, which have also made great progress in recent years.

“It’s sort of like Michael Jordan on the basketball court,” he said. “Great on its own, but it also makes all the other players better.”

Reference: “Accelerated aging of all-inorganic, interface-stabilized perovskite solar cells” by Xiaoming Zhao, Tianran Liu, Quinn C. Burlingame, Tianjun Liu, Rudolph Holley, Guangming Cheng, Nan Yao, Feng Gao and Yueh-Lin Loo, 16 June 2022, Science.
DOI: 10.1126/science.abn5679

The paper “Accelerated aging of all-inorganic, interface-stabilized perovskite solar cells” was published with support from the National Science Foundation; the U.S. Department of Energy, via Brookhaven National Laboratory; the Swedish Government Strategic Research Area in Materials Science on Functional Materials; and the Princeton Imaging and Analysis Center. In addition to Loo and Zhao, contributing authors include Tianjun Liu and Feng Gao, both from Linköping University; and Tianran Liu, Quinn C. Burlingame, Rudolph Holley III, Guangming Cheng and Nan Yao, all from Princeton University.


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