Understanding of Electrolyte Additives Will Improve Dye-Sensitized Solar Cells

An Australian research team has demonstrated that the molecules 4-tert-butylpyridine (tBP) and 1-methyl-benzimidazole (NMBI) play a role of crucial importance, as optimal additives, in maximizing the performance of copper redox meditators. An improved understanding of the role that additives play in optimizing electrolytes may lead to more consistent dye-sensitized solar cells (DSC) for low-light conditions.

That heightened understanding derives from research funded by the Australian Centre for Advanced Photovoltaics (ACAP) and supported by the ARC Centre of Excellence in Exciton Science. The researchers identified a combination of additives that most efficiently suppresses recombination losses, resulting in improved solar cell performance.

A prototype of a dye-sensitized solar cell prototype device. Courtesy of Monash University.

Dye-sensitized solar cells have achieved efficiencies of up to 34% at 1000 lux from a fluorescent lamp. The cells use copper-based electrolytes containing various combinations of additives to achieve these efficiencies, with varying results.

“Researchers were previously a bit worried because tBP can interact with copper complexes and everyone said, ‘Let’s try to avoid it.’ People thought this is detrimental to the solar cell performance, but we had a closer look at this,” joint first author Sebastian Fürer of Monash University and Exciton Science said. “We actually found that it’s really important to keep it in because it reduces one of the main loss mechanisms.”

Employing the correct additive in new copper redox mediators will now likely become standard in future efforts to improve DSC performance, Fürer said. “You can’t leave it out, because the solar cell goes from 9% efficiency to less than 1%. It is really a huge difference.”

“Our findings identify crucial performance-deterring loss mechanisms and are a step further toward the development of low-cost charge transporting materials for next-generation solar cells,” joint first author Rebecca Milhuisen, also of Monash University, said.

Additionally, senior author Udo Bach of Monash University believes the findings will enable researchers to successfully design and create a more efficient next generation of materials.

“Printable low-cost dye-sensitized solar cells have seen a considerable efficiency boost over the past years,” Bach said. “In our paper we reveal previously unknown details about the interplay of these compounds with other additives in the cell, which are the key to their outstanding performance.”

The research was published in Advanced Energy Materials (www.doi.org/10.1002/aenm.202002067).