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This coating boosts the efficiency of perovskite solar cells

| By Mary Page Bailey

Perovskite materials have great potential as a lightweight and low-cost option for solar panels, but in the past have not been seen as stable or durable enough for widespread use in large-scale solar-power installations. Now, a new coating developed by a research team at Purdue University (West Lafayette, Ind.;, led by chemical engineering professor Letian Dou, could overcome these challenges. “Perovskite can degrade quickly when exposed to moisture, heat or light, which limits its commercial application. Our organic ligand coating can reduce perovskite defects and passivate the surface, making the material much more stable. At the same time, the organic ligand can act as a semiconductor to help conduct charge, which helps to improve electrical performance,” explains Dou.

While much work has been done to develop coatings to protect and passivate perovskite, many of these options focused on insulating materials that actually decreased charge transport, adds Dou. The ligand is a bipolar, conjugated molecule — one end is charged to bind with the perovskite, while is the other is hydrophobic to protect against moisture. To form the coating, the ligand is dissolved in a solvent at a dilute concentration (typically less than 1 mg/mL). According to Dou, the cost to manufacture the ligand is very low, and based on well-established methods. Furthermore, the perovskite surface only requires a very thin coating — just 4–5 nm — meaning that the coating would not add significant cost to solar panels.

Over a 2,000-h testing period at high heat, the coated panel maintained over 80% of its original power conversion efficiency. “This is much higher performance than the control device without the ligand coating,” says Dou. Next, the team is considering ligands with new functional moieties and multiple binding sites to further enhance stability, and investigating ways to enhance solubility and processability to improve coverage. They also have a contract with a major solar-power company to begin testing the technology.