A research team, led by Professor Yang Chang-deok at Ulsan National Institute of Science and Technology (UNIST), recently synthesized high-quality perovskite thin films by adding a substance derived from camphor trees. It is expected to improve the lifespan and efficiency of perovskite solar cells due to the absence of residual materials, and to reduce manufacturing costs by simplifying the process.
In perovskite thin films used in solar cells, scientists tend to look for large crystal size and uniform arrangement, to allow a smooth flow of electrons and sturdy structure. Additives are used to create such high-quality films, but if residuals remain following manufacturing, they can 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 achieved 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.
