One-Step Polyelectrolyte Production Boosts Efficiency of Organic Solar Cells

A team of researchers from Pukyong National University discovered a simple method for creating polyelectrolytes and adjusting their properties to increase the efficiency of solar cells. These findings were recently published in Organic Electronics.

Organic solar cells (OSCs) are essential in reducing global reliance on fossil fuels. New technological developments have steadily improved their efficiency and affordability over the last few decades.

One particularly promising strategy is to apply specialized polymers known as "polyelectrolytes" to improve their performance. However, producing these materials at the purity levels needed for OSC use has been challenging thus far.

Joo Hyun Kim and colleagues at Pukyong National University in Busan, South Korea, have published new research that presents a novel, straightforward method for synthesizing high-purity polyelectrolytes and applying them to OSCs.

Such an innovation holds the promise of revolutionizing the field by offering a more accessible and efficient means of enhancing the performance of organic solar cells.

Joo Hyun Kim, Pukyong National University

Positively and negatively charged ions dissolved in a solution combine to form polyelectrolytes. Researchers have previously demonstrated how the polymers can be used as the "cathode interlayer," or the thin layer of material between the cell's active layer, which converts incoming sunlight into electricity, and the cathode, where electrons leave the cell.

This increase in efficiency is brought about by the unique electronic structure of polyelectrolytes, which lowers resistance to the flow of electrons from the active layer to the cathode while improving the collection of electrons generated in the active layer.

In the approach to polyelectrolyte production that is currently prevalent, the removal of excess starting materials remains a laborious and time-intensive task. Consequently, the simpler purification method that we propose heralds a promising avenue for improving the efficiency of organic solar cells.

Joo Hyun Kim, Pukyong National University

Kim's group used a novel chemical process to assemble polyelectrolytes, eliminating the need for excess starting materials.

The polyelectrolytes we used incorporate an ionic group into the polymer side chain, rendering them soluble in alcohol. We introduced an ion exchange technique for modifying these polymers, aiming to utilize them as cathode interlayers in OSCs.

Joo Hyun Kim, Pukyong National University

In this straightforward procedure, the dissolved polyelectrolyte's negative charges were swapped for other charges in the surrounding alcohol solution. By adjusting the interactions between the ions of the dissolved polymer, the researchers could control the properties of the polyelectrolyte that resulted from the joining of these molecular building blocks.

Kim's group was able to customize a robust performance in the cathode interlayer of the OSC without having to undergo laborious purification. In their experiments, the group increased the efficiency of converting sunlight into electricity by more than 9 %.

Kim concluded, “The results suggest that these polyelectrolytes show great potential for serving as a cathode interlayer in organic solar cells. They also offer the added benefit of enhancing interfacial properties through a straightforward anion exchange process, eliminating the need for complicated purification steps.”

The team now hopes that the approach could be applied more widely, accelerating the global rollout of renewable solar energy and further reducing the reliance on fossil fuels.

Journal Reference:

Kim, H. J., et al. (2024) A simple approach for improving the photovoltaic efficiency of organic solar cells through polymer modification via anion exchange as the interlayer. Organic Electronics. doi.org/10.1016/j.orgel.2024.106995