Researchers at the Pohang University of Science & Technology (POSTECH) have developed eco-friendly-solvent processable hole transport polymers by using peppermint oil and walnut aroma food additives and the polymer can prevent lead leakage.

The POSTECH research team consisted of Prof. Taiho Park and Junwoo Lee, that developed Alkoxy-PTEG - hole transport polymers that could be dissolved in peppermint oil, by applying ethylene glycol side chains when producing perovskite solar cells. Also, the team confirmed that this polymer captured leaking lead in aging perovskite solar cells.

The research team processed the perovskite solar cells using peppermint oil as a solvent without any chemical additives and the solar cell efficiency reached 19.9% and 21.2% when walnut aroma food additives were used. Furthermore, a disadvantage of the conventional perovskite solar cell is that it has low stability because of susceptibility to moisture. However, the newly developed polymers overcame this disadvantage and the research team verified that they kept 88% efficiency after 30 days passed and exhibited high stability.

In the meantime, they conducted magnetic resonance analysis and confirmed that the ethylene glycol side chains in the aged perovskite solar cells kept lead with moderate strength. They finally accomplished developing multifunctional hold transport polymers that could be eco-friendly solvent processed and prevent lead leakage. In other words, they kept leaked lead without destroying structures of the perovskite. Their achievement is expected to be a solution for environmental pollution issues caused by lead leakage, a chronic problem of the perovskite solar cells.

Junwoo Lee said: "When we use green solvent in the production process and prevent lead generated by the aged perovskite solar cells with a polymer, we can solve environmental issues of the high efficiency perovskite solar cells and mass produce them".

Prof. Taiho Park also commented: "Our research showed the world's highest efficiency of the perovskite solar cells which went through an eco-friendly process without any toxic substances added. We anticipate that this can be a solution to lead leakage of the conventional perovskite solar cells which harms human bodies or causes environmental problems."



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