Scientists in China have developed a new passivation method that has resulted in the design of a new perovskite-silicon tandem solar cell with a power conversion efficiency of more than 33 percent.

The research was carried out by scientists from the Ningbo Institute of Materials Technology and Engineering (NIMTE) of the Chinese Academy of Sciences (CAS). They were also joined by experts from Soochow University, Taizhou University, and smart equipment supplier S.C Exact Equipment Co.

For the project, the scientists came up with a new passivation strategy, which they believe could bring tandem solar cells closer to mass adoption. It improved both the efficiency and long-term stability of perovskite-silicon tandem solar cells.

Ye Jichun, PhD, a professor at the Ningbo Institute of Materials Technology and Engineering (NIMTE) and corresponding author of the study, emphasized the significance of the achievement. “This strategy is simple and compatible with existing industrial production lines, bringing perovskite/silicon tandem solar cells a step closer to commercial applications,” he added.

Better solar cells

Perovskite-silicon tandem solar cells, which combine a perovskite top layer and a traditional silicon bottom cell, are one of the most promising technologies in the future of photovoltaics (PV). They’re highly efficient and relatively cheap, because of the inexpensive materials used in their design.

The technology has strong optical absorption and long carrier diffusion lengths. It holds great potential for lightweight, high-efficiency applications in the PV field, and has attracted massive attention in recent years. The world record efficiency for such devices is about 35 percent.

That said, producing these cells is difficult. Industrial silicon substrates feature tiny pyramid-like textures designed to trap light more effectively. Even though this is essential for the cells’ performance, it leads to localized electrical leakage, and as a result, limits the commercial prospects of the cells.

To address the issue and suppress electrical leakage, the research team developed an innovative peak-selective passivation strategy. It uses polystyrene nanospheres as a template to precisely deposit a thin insulating layer of aluminum oxide onto the pyramid peaks. This blocks leakage pathways.

Great solar improvement

The new strategy delivered impressive results. By utilizing it, the team produced a perovskite-silicon tandem solar cell, with a power conversion efficiency of 33.33 percent. It also hit a certified efficiency of 32.89 percent across an active area of about one square centimeter.

At the same time, the tandem solar cell exhibited strong durability. It reportedly retained around 90 percent of its original efficiency after operating continuously for 1,000 hours.

The scientists pointed out that the approach could offer an important advantage for future industrial adoption because it is relatively simple and compatible with existing manufacturing lines.

According to the scientists, the method represents a valuable advance in tandem solar cell design. “This strategy improves the efficiency and operational stability of perovskite/silicon tandem solar cells by selectively passivating the peaks of the pyramid-textured silicon bottom cells,” the team concluded in a press release.

The study has been published in the journal Matter on May 21.