Researchers at KAUST have developed a multifunctional molecule that can plug various atomic-scale defects in perovskite solar materials, which could significantly boost the longevity and electrical output PSCs.
Perovskites inevitably feature defects, such as where a particular ion did not slot into place during fabrication, leaving a gap in the structure. These reactive sites can contribute to rapid performance decline — unless they can be fixed. “Defect passivation is very important for improving the long-term stability of perovskite solar cells,†says Furkan Isikgor, a researcher in Stefaan De Wolf’s group.
“PhenHCl works very well owing to its multifunctional structure,†Isikgor says. The molecule consists of an electro-positive ammonium head group that can plug negatively charged defects and an electro-negative amine and imine group body to plug positive gaps.
The researchers showed that PhenHCl boosted the power conversion efficiencies (PCEs) of wide bandgap perovskites from 16.7% in untreated cells up to 20.5% in treated cells. “Moreover, PhenHCl passivation improves the PCE of textured perovskite/silicon tandem solar cells from 25.4% to 27.4%,†Isikgor says.
PhenHCl passivation also significantly improved the stability of the perovskite solar cell. “Under continuous light soaking, the PhenHCl-passivated device retained 80% of its post-burn-in efficiency for around 106 hours of operation,†Isikgor says. The untreated device retained 80% of its post-burn-in efficiency for only 5 hours.
“Our simple holistic defect-passivation strategy has drastically improved the semiconductor quality of solution-processed perovskites,†says De Wolf. “Passivating the different types of defects that may be present in perovskites with a single molecule is highly attractive for industry,†he adds. The next step will be to integrate PhenHCl passivation with scaled-up perovskite production. “Simultaneously, we are working on further improvements in device performance and stability through extensive outdoor testing,†De Wolf adds.