A team of Princeton Engineering researchers have developed the first perovskite solar cell with a commercially viable lifetime. The team projects their device can perform above industry standards for around 30 years.
It is the first of its kind to rival the performance of silicon-based cells, which have dominated the market since 1954. Perovskites are semiconductors with a special crystal structure that makes them well suited for solar cell technology. They can be manufactured at room temperature, using much less energy than silicon, making them cheaper and more sustainable to produce. And whereas silicon is stiff and opaque, perovskites can be made flexible and transparent. However, perovskites are fragile; solar cells (PSC) created between 2009 and 2012, lasted only minutes. Later in 2017 a device was created that could operate under continuous illumination at room temperature for one year.
The Princeton team, led by Lynn Loo, Professor in Engineering, revealed their new device and their new method for testing such devices in a paper published June 16 in Science.
Loo commented that the record-setting design has highlighted the durable potential of PSCs, especially as a way to push solar cell technology beyond the limits of silicon. But she also pointed past the headline result to her team’s new accelerated aging technique as the work’s deeper significance.
Due to perovskites’ well-known frailty, long-term testing wasn’t available. Now, as the devices get better and last longer, testing one design against another will become crucial for fabricating durable, consumer-friendly technologies.
Efficiency has accelerated at a remarkable pace over the past decade but the stability of these devices has improved more slowly. Therefore, testing will need to become more sophisticated.
According to a release in Science Daily, “In early 2020 Xiaoming Zhao, a postdoctoral researcher in Loo’s lab, had been working on a number of designs with colleagues. The efforts layered different materials in order to optimize light absorption while protecting the most fragile areas from exposure. They developed an ultra-thin capping layer between two crucial components: the absorbing perovskite layer and a charge-carrying layer made from cupric salt and other substances. The goal was to keep the perovskite semiconductor from burning out in a matter of weeks or months, the norm at that time.”
In the fall of that year,when researchers returned to their labs, Zhao noticed one set of the devices still seemed to be operating near its peak efficiency, realizing he needed a way to stress test his device faster than his real-time experiment allowed.
The new testing method speeds up the aging process by illuminating the device while blasting it with heat, accelerating what would happen naturally over years of regular exposure. The researchers chose four aging temperatures and measured results across these four different data streams, from the baseline temperature of a typical summer day to an extreme of 230⁰F.
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.
Loo said new PSCs 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.
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.
