Wood-based organic solar cells, the new frontier of photovoltaics

From waste paper, the second raw materials for organic photovoltaics

The new frontier of photovoltaic economic and sustainable? The innovative wood-based organic solar cells created by a team of researchers in Sweden. In this case the wood, or more precisely the lignin extracted from its pulp, served to create a particular component of the cell: the state of transport of the charges in contact with the cathode.

This is a significant step on the road to the stability of this technology. Low production costs, lightness and flexibility have always distinguished the organic photovoltaic opening doors to an innumerable range of applications. The weakness of this segment, now that efficiency has also reached useful values, remains stable. Unlike crystalline silicon and other inorganic semiconductors, this type of photovoltaic suffers from increased sensitivity to oxidation, reduction, recrystallization and temperature changes, which can lead to device degradation and performance reduction over time.

Wood-based organic solar cells, are more reliable

Previous experiments have already shown that lignin could increase the reliability of organic solar cells as well as perovskite cells. But until yesterday a version of the polymer was used that was heavily treated with various chemicals. The Linköping team wanted to make the process greener by using a much more “rough” lignin, called kraft lignin. It is a waste product of paper production and therefore it is also cheap to find.

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“We have created a kraft lignin composite that will be the contact surface with the cathodic layer,” says Qilun Zhang, first research engineer at the Linköping University Organic Electronics Laboratory. “It turned out that the solar cell had become much more stable. The advantage of lignin kraft is that it can create many hydrogen bonds, which helps stabilize the cell”.

“Organic solar cells will never be the best in terms of efficiency,” adds Professor Mats Fahlman. “But the advantage is that they are non-toxic, durable and economical. If they can achieve 15-20% efficiency, it will work for most applications“. The search results appeared in Advanced Materials 2023.