Materials scientists at the UCLA Samueli School of Engineering and researchers from five other varsities recently demonstrated a simple surface adjustment in the manufacturing of perovskite solar cells to overcome the degradation of cells due to prolonged exposure to sunlight.

Perovskites are a group of materials with the same atomic arrangement or crystal structure as the mineral calcium titanium oxide. This research focuses on metal halide perovskites, a subgroup of perovskites, owing to their promising application for energy-efficient, thinfilm solar cells.

The research was led by Yang Yang, a UCLA Samueli professor, and the research paper was co-authored by Shaun Tan and Tianyi Huang, UCLA Samueli Ph.D. graduates.

The research was supported by the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy.

What degrades efficiency in Perovskite Solar Cells?

The perovskite solar cells are most commonly subjected to a surface treatment to remove defects, wherein a layer of organic ions is deposited to treat the defection. This results in the creation of a more electron-rich surface which is a potential trap for energy-carrying electrons.

When the energy-carrying electrons are trapped, the orderly arrangement of atoms in the cells destabilizes — making perovskite solar cells less efficient over time. Ultimately, this makes the solar panels with perovskite unattractive for commercialization.

The New Surface Treatment

In order to resolve the long-term degradation of perovskite solar cells, scientists paired the positively charged ions with the negatively charged ions and discovered a new surface treatment process. The change enabled the surface to be more electron-neutral and stable while preserving the integrity of the defect-prevention surface treatments.

The team then tested the endurance of these cells in the lab under accelerated aging conditions and illumination designed to mimic sunlight.

During the experiment, these cells retained 87% of their original sunlight-to-electricity conversion performance for over 2,000 hours. However, the solar cells with commonly used surface treatment mechanism dropped 65% in their performance when they were tested under similar settings.

Shaun Tan, the research co-author, said,  “Our perovskite solar cells are among the most stable in efficiency reported to date. We’ve laid new foundational knowledge on which the community can further develop and refine our versatile technique to design even more stable perovskite solar cells.”

The manufacturing cost of solar cells based on perovskite technology is much lower than its silicon-based counterparts — making it the best suitable energy-efficient converter. The new surface treatment process aims to make perovskite solar cells more accessible by addressing the issue of solar cell degradation due to exposure to direct sunlight.

Recently, researchers at the King Abdullah University of Science and Technology (KAUST) developed a new technology to help perovskite solar cells withstand prolonged exposure to high humidity and elevated temperatures.

Image credit: UCLA Samueli School Of Engineering