Adapting perovskite solar cells for renewable energy

Researchers at City University of Hong Kong (CityU) have engineered a unique type of self-assembled monolayer, or SAM for short, and anchored it on a nickel oxide nanoparticles surface as a charge extraction layer. This could have significant implications for the development and commercialisation of perovskite solar cells. Professor Zhu Zonglong, from the Department of Chemistry at CityU, said the potential applications of this research could revolutionise the solar energy industry.

Perovskite solar cells are known for their impressive power conversion efficiency. However, they have a significant drawback: thermal instability, as they do not perform well when exposed to high temperatures. The self-assembled monolayer (SAM) developed by researchers enhanced the thermal robustness of the cells, with Zhu explaining that thermal stability is a barrier to the commercial deployment of perovskite solar cells.

“By introducing a thermally robust charge extraction layer, our improved cells retain over 90% of their efficiency, boasting an impressive efficiency rate of 25.6%, even after operated under high temperatures, around 65℃ for over 1000 hours. This is a milestone achievement,” Zhu said.

The researchers focused on the self-assembled monolayer (SAM) and envisioned it as a heat-sensitive shield that needed reinforcement. They discovered that high-temperature exposure can cause the chemical bonds within SAM molecules to fracture, negatively impacting device performance. “Our solution was akin to adding a heat-resistant armour — a layer of nickel oxide nanoparticles, topped by a SAM, achieved through an integration of various experimental approaches and theoretical calculations,” Zhu said.

To counteract this issue, the researchers anchored the SAM onto an inherently stable nickel oxide surface, thereby enhancing the SAM’s binding energy on the substrate. They also synthesised a new SAM molecule, creating an innovative molecule that promotes more efficient charge extraction in perovskite devices. The primary outcome of the research is the potential transformation of the solar energy landscape. By improving the thermal stability of perovskite solar cells through the SAMs, the researchers have laid the foundation for these cells to perform efficiently even in high-temperature conditions.

“This breakthrough is pivotal as it addresses a major obstacle that previously impeded wider adoption of perovskite solar cells. Our findings could significantly broaden the utilisation of these cells, pushing their application boundaries to environments and climates where high temperatures were a deterrent. This technology, once fully commercialised, could help decrease our dependence on fossil fuels and contribute substantially to combating the global climate crisis,” Zhu said.

The research findings have been published in the journal Science.

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