A joint research team from UNIST and KAUST has developed an interface coating technology for perovskite-silicon tandem solar cells that achieves an efficiency of over 31% even when fabricated in a normal atmospheric environment. This achievement reduces moisture vulnerability and reproducibility issues, which have been identified as burdens in the production process of high-efficiency tandem cells.

UNIST announced on the 11th that a team led by Distinguished Professor Sang-Il Seok of the Department of Energy and Chemical Engineering and Professor Kyung-Jin Choi of the Department of Materials Science and Engineering developed a three-component interfacial coating material in collaboration with a research team from KAUST in Saudi Arabia. The results of this research were published in the international journal Nature Photonics on the 1st.

Perovskite-silicon tandem solar cells have a structure in which perovskite cells and silicon cells are stacked to absorb light of different wavelengths. Research is continuing as a next-generation solar technology because higher theoretical efficiency can be expected compared to conventional single silicon solar cells.

The challenge to commercialization is process stability. Conventional self-assembled monolayers and SAM interface layers are sensitive to moisture in the air, making it difficult to form them uniformly on the electrode surface, and their structure can become disrupted during subsequent solution processes. For this reason, a special environment that controls moisture and oxygen was required to manufacture high-efficiency devices.

The research team applied a three-component coating layer containing GDMA and AG to the existing SAM material, Me-4PACz. GDMA enhances the uniformity and adhesion of the coating layer on the electrode, while AG reduces interfacial defects in contact with the perovskite. Reduced interfacial defects decrease light-generated charge loss, leading to improved voltage and efficiency.

The tandem solar cell with the coating layer recorded a photoelectric conversion efficiency of 31.72% under normal atmospheric manufacturing conditions. The certified efficiency was confirmed to be 31.36%. It maintained over 92% of its initial performance even after being exposed to an 85-degree environment for 600 hours without protective packaging, and maintained over 90% efficiency even after being irradiated with simulated sunlight for 1,000 hours.

The research team explained that this technology can also be applied to the fabrication of perovskite single cells. Thin film uniformity was confirmed even on a large-area 7×7 cm² substrate, demonstrating the potential for expansion into large-area manufacturing processes in the future.

UNIST researcher Kim Gwi-soo, KAUST researcher Adi Prasetio, and UNIST researcher Noh Young-im participated in this study as co-first authors. Professors Seok Sang-il and Choi Kyung-jin, along with KAUST Professor Stefan de Wolf, served as co-corresponding authors.