GIST Develops Interfacial Control Technology to Prevent High-Temperature Degradation in Organic Solar Cells
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by Min Chanki
Published 26 Aug.2026 15:01(KST)
The Gwangju Institute of Science and Technology (GIST) announced on August 26 that the research team led by Kwanghee Lee, head of the “World’s First Perovskite Solar Cell Commercialization Strategy Research Project Group” (hereinafter referred to as the Strategy Research Project Group) and Distinguished Scholar in the Department of Materials Science and Engineering, has uncovered the cause of efficiency degradation in organic solar cells at high temperatures and developed a new interfacial control technology to suppress it.
(From left) Kwanghee Lee, Head of Strategic Research Project Group; Hongkyu Kang, Deputy Director of Next Generation Energy Research Institute; Saanseong Lee, Ph.D., Researcher at High-Purity New Material Research Center. Provided by GIST
The organic solar cells utilizing this technology maintained their initial power conversion efficiency of approximately 18.1% almost entirely, even after operating for more than 2,000 hours at 85°C. Notably, the typical phenomenon of ‘burn-in loss’—a rapid initial performance drop commonly observed in organic solar cells—was not detected.
Organic solar cells, which use organic materials to convert sunlight into electricity, are a key material for solar panels. Compared to silicon solar cells, they are lighter, more flexible, and can be manufactured at relatively low temperatures using solution processing. However, their vulnerability to heat remains a major barrier to commercialization. Since real-world photovoltaic environments can expose solar cells to high temperatures from sunlight, technologies that can maintain stable performance during prolonged use are necessary.
The research team focused not on the photoactive layer that generates power in organic solar cells, but on the “interface”—the region between the photoactive layer and the electrode that facilitates charge transport. When exposed to sunlight, organic solar cells generate electrons and ‘holes’ (positions where electrons have left). These charges migrate to respective electrodes to produce electricity. Among the layers, molybdenum oxide is widely used as the “hole transport layer” that helps holes reach the electrode. The problem is that molybdenum oxide cannot stay in place at high temperatures.
The researchers heated the organic solar cells at 85°C and tracked changes inside the device. They observed that at high temperatures, molybdenum oxide gradually diffused away from its original position and into the photoactive layer, which is responsible for generating electricity. This migrating molybdenum oxide created defects in the photoactive layer that hindered charge transport, thereby impairing the collection of charges at the electrode. As a result, the power output of the solar cell decreased. The team concluded that the physical migration of molybdenum oxide into the photoactive layer is a more critical factor for high-temperature performance degradation than changes in its electrical properties.
Oxygen defects formed on the surface of molybdenum oxide at high temperatures and the defect suppression effect of PBN.
The team hypothesized that if molybdenum oxide could be stabilized at the interface, such high-temperature deterioration could be suppressed. To achieve this, they introduced a small molecule called ‘PBN’ between the molybdenum oxide and the photoactive layer. PBN contains a nitrone functional group—a chemical motif with distinctive properties. This group interacts strongly with unstable regions on the molybdenum oxide surface, stabilizing it and suppressing the formation of ‘oxygen defects’ caused by oxygen loss at high temperatures. In short, PBN acts as a protective barrier at the interface, preventing molybdenum oxide from migrating into the photoactive layer.
Actual application of PBN to solar cells demonstrated highly stable performance at elevated temperatures. Organic solar cells with PBN retained their initial power conversion efficiency of around 18.1% at virtually 100% even after 2,000 hours at 85°C. In contrast, solar cells without PBN saw their efficiency decrease by about 20% after just 2 hours of high-temperature exposure, and by about 25% after 24 hours. To confirm the crucial role of the nitrone functional group in PBN, the research team conducted comparative tests using PBtA—a molecule similar to PBN, but without the oxygen atom that forms the nitrone group. PBtA was far less effective at stabilizing molybdenum oxide than PBN, confirming that the nitrone functional group in PBN is essential for interfacial stabilization of molybdenum oxide.
To determine whether the new technology was effective only with certain combinations of materials, the team applied PBN to two different types of organic solar cells made from different material sets. In both cases, cells with PBN maintained nearly their initial efficiency at 85°C, whereas those without PBN experienced rapid performance decline. This result demonstrates that the technology is not limited to specific material types, but can be broadly applied to suppress high-temperature performance degradation in various kinds of organic solar cells.
Kwanghee Lee, head of the Strategy Research Project Group, said, “This research is significant because it has identified the key mechanism for high-temperature performance degradation in organic solar cells and proposed an interfacial strategy to directly suppress the problematic material’s movement.” He added, “We expect this technology will not only enhance the long-term operational stability of organic solar cells but also be applicable to perovskite solar cells and organic–perovskite tandem solar cells as next-generation photovoltaic devices.”
Hongkyu Kang, Deputy Director of the Next Generation Energy Research Institute, stated, “We plan to expand this interfacial control technology—demonstrated in small-area devices—to large-area modules, and to develop it into an industry-ready technology through long-term reliability testing and collaborative research with industry partners.”
This study, jointly led by Kwanghee Lee of GIST’s Strategy Research Project Group and Hongkyu Kang of the Next Generation Energy Research Institute as corresponding authors, and Sanseong Lee, Ph.D. of the Heeger New Materials Research Center as first author, involved collaboration with researchers from Pohang University of Science and Technology (POSTECH), Åbo Akademi University (Finland), Linköping University (Sweden), Kyonggi University, Chonnam National University, Korea Basic Science Institute (KBSI), and Korea Institute of Science and Technology (KIST). It was supported by the Ministry of Climate Energy Environment and Korea Institute of Energy Technology Evaluation and Planning, the Ministry of Science and ICT and the National Research Foundation of Korea, the Ministry of Education and the National Research Foundation of Korea (LAMP Project), the Ministry of SMEs and Startups, and the Ministry of Science and ICT’s GIST Strategy Research Project (ISD). The results were published online on July 31, 2026, in “Small”—an international journal in the field of materials science.
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