Perovskite solar cells achieve 27.2% efficiency due to improved chlorine distribution

In recent years, perovskites have emerged as a promising solution for cheaper and more efficient solar energy. This advanced synthetic material is made from crystals that mimic naturally occurring crystalline perovskite (calcium titanate).

Among the issues holding it back are achieving the maximum possible power from sunlight and achieving long-term durability. But researchers at the Semiconductor Research Institute, part of the Chinese Academy of Sciences, have developed a technology that could break the world record for efficiency and improve the durability of solar cells.

The main problem that prevents perovskite solar cells from realizing their potential is the use of a chemical called methylammonium chloride (MACI) in the manufacturing process. This helps the crystals grow, but scientists have found that during the heating process, the chloride ions begin to migrate and clump together and clump near the top and embedded surfaces of the membrane. This film is a thin layer of perovskite material located inside the solar cell, and the uneven distribution of chloride ions limits its maximum output.

simple solution

The research team has published a solution to the chlorine agglomeration problem in the journal Science, and it’s surprisingly simple. They simply added an alkali metal oxalate (potassium dioxalate) to the liquid perovskite mixture before making the film.

When this new ingredient is added, potassium ions are dissolved and released and attach to the migrating chloride ions to form a new stable salt (potassium chloride). As a result, the chlorine is distributed evenly and homogeneously, preventing the formation of defects.

“Our strategy to homogenize the chlorine distribution not only increases the efficiency but also significantly increases the operational stability of perovskite solar cells,” said corresponding author Jingbi You. “This could be a game-changer for the commercialization of perovskite solar power.”

record-breaking achievements

Researchers have conducted extensive tests on new perovskite solar cell devices and achieved record results in several areas. They demonstrated a power conversion efficiency (PCE) of 27.2%. This means that the solar cells successfully convert 27.2% of the total energy from sunlight hitting the panels into usable electricity. This has been independently verified to be the world’s leading standard for perovskite solar cells.

The device also maintained 86.3% of its initial efficiency after 1,529 hours of continuous operation at full power under solar illumination. It also maintained an internal efficiency of 82.8% after 1,000 hours of operation at 85 degrees Celsius in full sunlight.

Although the researchers have dramatically improved the distribution of chlorine, they admit there is still work to be done, as some uneven spots remain.

They also found numerous defects at the buried interface, the boundary between the perovskite layer inside the solar cell and the rest of the structure. The next step will focus on reducing defects and creating a more uniform layer.

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