Stabilizing ligand enables 22% efficiency in all-inorganic perovskite cells

An international team of physicists, chemists and electronic engineers reports that a stabilizing ligand enables all-inorganic perovskite cells with an efficiency of up to 22%. In their study, published in the journal Nature, the group came upon the idea of introducing para-toluenesulfonyl hydrazide (PTSH) as a stabilizing ligand to promote the formation of films during the crystallization process.

Prior research has shown that perovskite can replace silicon in solar cells. Unfortunately, use of the calcium-titanate-based mineral has suffered from manufacturing and scaling problems. This is because, to date, such efforts have involved the use of organic cations. In this new effort, the researchers tested the possibility of using inorganic cations, resulting in all-inorganic perovskite solar cells with reasonable efficiencies.

The researchers have thus far tested the cations rubidium and cesium and have addressed the known problems associated with crystallization, scaling and oxidation of metals by introducing PTSH as a ligand to encourage the growth of films as the material crystallizes. This resulted in a protective environment rich in electrons and good at suppressing reactions that could degrade the process. They note that addition of the ligand worked to stabilize the metal halides that were used in creating the solar cells.

The research team also noted that the combination of PTSH and perovskite could be used with spin coating, one of the more common means of production for solar cells at an industrial level.

Testing of their demo cells showed an efficiency of just 17%—well below the general standard of 30% for silicon-based solar cells. But they noted their cells could also be used in tandem to make stacked solar cells. Doing so resulted in efficiencies as high as 22.57%. They also note that adding the ligand improved the durability of the solar cell—it maintained its structure at 80% after 1,500 hours of use at temperatures averaging 65°C and for 800 hours at 85°C.

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