In the field of photovoltaics, silicon is king. Without discussion. Crystalline silicon solar cells are estimated to represent about 95% of the photovoltaic market, an overwhelming percentage that does not prevent researchers from keep innovating in search of higher performance quotas. If what we are talking about is promises and expectations, however, the leading role probably belongs to other materials: the perovskite family, for many the “holy grail” of photovoltaic technologies due to its “optimal” properties for transforming solar energy into electrical.
Over the last few years its development has been noticeable and accelerated, especially when compared to the much slower pace that silicon experienced for decades. “When the first solar cell made with a perovskite was published in 2009, an efficiency of 3.8% was reported. It is a very low number. In addition, it degraded in hours. Right now they are at 25.5% and they do not degrade in hours ”, explained in 2021 Ignacio Mártil de la Plaza, professor of electronics at Complutense.
Far from pausing, development has continued, both in terms of perovskite cells and “tandem” devices that combine them with other silicon-based ones. To clear his future, however, he needs to make progress on several key fronts: improving his stamina, performance, and duration. A group of scientists from the University of Oxford, hand in hand with other Australian and US colleagues, have just taken a valuable step in bringing the durability of perovskite solar cells closer to that of silicon, a major achievement.
“If it doesn’t last, it won’t have as much value”
Their new contribution It does not go through an improvement focused on the materials or the design of the plates, but through a method of manufacturing stable perovskite cells, with fewer defects and, probably most interestingly, the potential to compete with the durability of silicon.
The key is how they are made: removing the dimethyl sulfoxide solvent and introducing dimethylammonium chloride, a small change that allowed the researchers to improve their control over the intermediate stages of the crystallization process. The result –need in ScienceDaily— are “higher quality thin films with reduced defects and greater stability.”
To see how effective the method was, the scientists experimented with a sample of 138 devices that they put to the test with an accelerated aging process at temperatures and in real conditions. The results invite optimism. The perovskite cells that they had created with the new synthesis process “significantly exceeded” to the control group and demonstrated their ability to resist heat, humidity and radiation.
The breakthrough is key to improving the efficiency of peroskite cells and making “tandem” devices that combine peroskite with silicon even more attractive. “It is very important that people start to realize that performance is worthless if it is not stable. If the device lasts a day or a week, or something like that, it won’t be as valuable. Plus it has to last for years.” reflects Philippe Holzhey, student at the University of Oxford and co-author of the work. The full study, led by Henry Snaith and Udo Bach, professors respectively at Oxford and Monash, can be be consulted in full in the prestigious magazine Nature Materials.
?Ammonium is the secret ingredient in stable, efficient & scalable perovskite solar cells, say @excitonscience @MonashUni and @CSIRO https://t.co/JIHWBK2IB3 pic.twitter.com/tsZdC0qCXp
— Au Science Media Ctr (@AusSMC) December 22, 2022
What exactly did the tests show? That when the prototype was subjected to more than 1,400 hours in simulated sunlight conditions at 65ºC, the best of the devices operated for more than 1,400 hours above the T80 threshold, a common industry benchmark indicating time It takes a solar cell to be reduced to 80% of its initial efficiency.
When scientists moved from 1,600 hours They checked other interesting answers: the control device they had made with the conventional method—using dimethyl sulfoxide—stopped working, while those made with the new improved design retained 70% of their original efficiency even under accelerated aging conditions. The performance of the new cells also improved to that of the control group when subjected to temperatures of 85ºC.
With the data already on the table, the researchers concluded that the new cells age at a factor of 1.7 for every 10ºC increase in the temperature to which they remain exposed, which is close to the increase expected for commercial silicon devices. “We have provided the research community with a second way to make high-quality perovskite solar cells,” claim from the Scimexwhich emphasizes that the new method indicates “a path to create a durable and efficient perovskite photovoltaic on an industrial scale”.
Semiconductor films made of perovskite compounds stand out for their flexibility and cost, among other factors, and over the last few years researchers have made progress to improve their efficiency. Recently, in fact, a group of scientists from the Helmhltz-Zentrum Berlin (HZB) they set a record upon achieving an efficiency of 32.5% with “tandem” solar cells made of silicon and perovskite, but key challenges remain to be resolved, such as their rate of degradation under real conditions compared to silicon cells.
Now the experts have managed to advance on that fundamental path.
Cover image: SCIMEX
