A substance derived from camphor tree has been reported to improve the quality of thin-film solar cells. This achievement makes use of the sublimation property of this substance, which transitions directly from solid to gas without going through a liquid phase, disappearing without a trace.
Research team led by Professor Yang Chang-deok at Ulsan National Institute of Science and Technology (UNIST) announced on the 29th that they synthesized high-quality perovskite thin films by adding a substance from camphor tree. It is expected to improve the lifespan and efficiency of solar cells due to the absence of residual materials, and to reduce manufacturing costs by simplifying the process.
The perovskite thin films used in solar cells utilize crystalline materials that have a perovskite structure as the light-absorbing layer, consisting of numerous crystallite particles. The larger the crystal size and the more uniform the arrangement, the smoother the flow of electrons, and the sturdier the structure, ultimately enhancing the efficiency and lifespan of the solar cells. Additives are used to create these high-quality structures, but if residuals remain following manufacturing, they can actually cause performance degradation.
To solve this issue, the research team used camphorquinone as a thin-film additive. Camphorquinone is a substance where an oxidation functional group is added to the camphor extracted from the camphor tree. It possesses sublimation properties like camphor, transitioning directly from solid to gas, but sublimates gradually unlike camphor. During the primary heat treatment process, it helps ensure uniform crystallization seeds, some of which sublimate, while the rest remain in the thin film long enough to grow crystals before completely sublimating during the secondary heat treatment.
Park Ji-won, the first author of the research paper, noted, "Camphorquinone can control the timing of its action to match the crystal growth stage without leaving any residues in the thin film," adding, "Thanks to these characteristics, we were able to produce high-quality thin films."
The solar cells using this crystalline thin film recorded a photoelectric conversion efficiency (PCE) of 25.2%. Photoelectric conversion efficiency refers to the effectiveness of converting solar energy into electrical energy. This figure is approximately 9.6% higher than the control group, which did not use additives (23.0%). Additionally, under maximum power point tracking (MPPT) conditions that simulated real operating environments, they maintained more than 90% of the initial efficiency for 1,000 hours and demonstrated more than double the lifespan performance compared to the control group. MPPT refers to the state where solar cells are set to deliver maximum output under artificial sunlight, one of the most challenging lifespan evaluation criteria.
Professor Yang Chang-deok stated, "It is significant that we can address the stability issues of perovskite solar cells with eco-friendly materials derived from nature," describing it as technology that can lead both the sustainability of the solar energy industry and technological advancement.
The research results were published on the 21st in 'Energy & Environmental Science,' the top academic journal in the field of eco-friendly energy.
References
Energy & Environmental Science (2025), DOI: https://doi.org/10.1039/D4EE03897E