Securing solar

How an innovative diazirine crosslinker is enabling ultra-stable prevoskite solar cells while limiting degradation.

Perovskite solar cells are showing strong potential as high performance alternatives to conventional silicon solar cells. As thin-film technology, perovskites provide a lighter-weight solar cell option that can be produced at a lower cost and deposited on a flexible base. This means new design and application opportunities for the way solar power is collected, and the potential for faster, more widespread expansion of the world’s capacity to generate solar energy.

While major advances have been achieved with rapidly rising power conversion efficiencies and scalable fabrication approaches, the long-term stability of perovskite solar cells when exposed to environmental stimuli has remained an obstacle to commercialisation.

Perovskite solar cells are built with layers of materials, either printed or coated from liquid inks, spin-coated, or vacuum-deposited. When exposed to heat and sunlight, the volatile organic components within the perovskite layer have a tendency to escape or migrate. This leads to degradation which significantly reduces their efficiency, stability and performance. While several strategies have been employed in the past to address this instability, none have been successful in providing perovskite solar cells with ongoing protection from environmental exposure.

Taking a novel approach to solving this stability challenge, researchers at Fudan University in Shanghai, China, used a molecular bis-diazirine crosslinker – a product called BondLynx, designed and manufactured by specialty chem-tech company XlynX Materials – to covalently bond the organic cations within the perovskite layer. The results were extraordinary.

ILLUMINATION STABILITY

BondLynx-treated perovskite solar cells showed remarkable stability, retaining nearly 99% of their initial efficiency even after 1,000 hours of continuous 1-sun illumination (1kW/m2). In comparison, untreated control perovskites exhibited a 35% loss in power conversion efficiency after just 200 hours of operation under the same conditions.

THERMAL STABILITY

When exposed to constant heat (60°C), untreated perovskite solar cells demonstrated poor thermal stability, losing 27% efficiency after 600 hours of continuous operation. By comparison, BondLynx-treated perovskite solar cells maintained nearly 98% efficiency under these conditions.

HIGH EFFICIENCY

Overall, BondLynx-treated perovskite solar cells achieved a high certified efficiency of over 24% with operational stability over 1,000 hours. With no significant reduction in performance over the course of the study, the stability improvements realised by BondLynx are expected to extend far beyond the 1,000-hour mark.

LIMITING LOSSES

The reason BondLynx is effective is because it forms covalent chemical bonds with the organic components in perovskites to strongly immobilise them, thereby limiting losses in efficiency, stability, and performance. BondLynx employs diazirine-based crosslinking technology which, when exposed to heat or UV light, produces highly reactive carbenes which crosslink with virtually any nearby aliphatic organic molecules containing C-H, O-H, or N-H bonds.

This diazirine-based approach has long been utilised in the field of chemical biology, and is being successfully applied by XlynX Materials to overcome adhesion challenges associated with low surface energy plastics, to add strength to performance textiles, and increasingly to stabilise organic components in semiconductors.

XlynX Materials is now actively working with solar cell manufacturers to conduct longer performance trials of its products and to help facilitate the incorporation of BondLynx into the perovskite fabrication process. If successful, this improved cell stability could prove to be a tipping point for the commercial viability of perovskite solar products. More broadly, these findings suggest a wide range of potential applications for diazirine technology in the field of organic electronics, something the team at XlynX Materials is eager to explore.