Researchers from the University of Surrey, the National Physical Laboratory and the University of Sheffield have embedded Al2O3 nanoparticles, which successfully trapped iodine, to improve the durability of perovskite solar cells (PSCs).
Device architecture of the PSCs used in this study (left) and a photograph of a device (right). Image from: Royal Society of Chemistry
Experiments conducted in extremely hot and humid conditions shown a tenfold increase in performance, lasting more than 1,530 hours as opposed to 160 hours without the alteration. According to the team, by increasing electrical conductivity, decreasing flaws, improving the homogeneity of the perovskite structure, and adding a moisture-resistant layer, the nanoparticles could open the door for more robust and reasonably priced solar technology.
PSCs have rapidly improved in power conversion efficiency since their debut in 2009. However, long-term stability remains a challenge. Unlike silicon-based solar cells, PSCs degrade due to factors like light, heat, moisture, and oxygen. The degradation, according to the team, mainly occurs because of the generation of molecular iodine (I2), which can penetrate the perovskite layer, causing chain reactions that further deteriorate the device. To enhance PSC stability, strategies to trap I2 are crucial.
A viable alternative is gamma-alumina (γ-Al2O3), which is well-known for its strong reactivity with I2. By creating stable surface complexes, it absorbs I2 and stops additional deterioration. Al2O3 nanoparticles (NPs) were employed in PSCs in earlier research to improve stability by preventing metal ion migration and increasing the perovskite layer’s wettability.
When combined with self-assembled monolayers (SAMs) such as Me-4PACz, which facilitate quick hole extraction but have wettability issues, Al2O3 NPs are especially successful. Researchers achieved efficiency near 20 percent by altering Me-4PACz with Al2O3 NPs, improving layer formation and recombination durations. This technique has gained popularity for enhancing PSC performance and stability.
Subsequent investigation showed that the AlO₃ nanoparticles improved electrical conductivity and reduced flaws in the perovskite structure, forming a protective 2D perovskite layer that serves as an extra barrier against moisture deterioration.
“By addressing these common challenges we see with perovskite solar technology, our research blows the doors wide open for cheaper, more efficient and more widely accessible solar power,” said Dr. Imalka Jayawardena, Marcus Lee Lecturer at University of Surrey, in a statement.
Experiments showed that perovskite solar cells (PSCs) with Al2O3 nanoparticles (NPs) last 1530 hours before their efficiency drops to 80 percent of the original level. These tests were done under conditions of 65°C and 35 percent humidity.
The researchers found that these solar cells last over ten times longer than those made with PFN–Br. The cells with Al₂O₃ nanoparticles kept an efficiency of 13.1 percent after about 1520 hours, starting from 16.4 percent. For these tests, they used copper instead of silver for one of the cell’s layers.
The addition of Al2O3 NPs has various advantages, which contribute to the increased stability. Al2O3 NPs efficiently retain I2, lowering its release from the perovskite layer during heat stress, according to optical spectroscopy. This prolongs the life of the cells by limiting deterioration.
Furthermore, compared to those on PFN-Br, perovskite layers grown on Al2O3 NPs displayed a more consistent surface potential, suggesting improved electrical uniformity and material consistency inside the layer.
According to the team, the study reveals a significant but an unrecognized function of Al2O3 NPs in PSCs. Al2O3 NPs function as a nanoengineered interlayer that enhances structural and electrical characteristics, opening the door to more reliable and effective PSCs.
“With these improvements, we’re breaking new ground in stability and performance, bringing perovskite technology closer to becoming a mainstream energy solution, said Hashini Perera, a postgraduate research student at University of Surrey’s Advanced Technology Institute and lead author of the study, in a statement.
