Cesium-enhanced perovskite solar cells 21.1% more efficient

A group of EPFL scientists in Switzerland have added cesium, a soft, silvery-gold alkali metal, to perovskite solar cell, to address heat stability and long-term efficiency issues. By doing so, the team of scientists led by Michael Grätzel's lab at EPFL, has now developed a perovskite solar cell with efficiency of 21.1%, as well as record-level reproducibility. The work is published in Energy and Environmental Science.

By adding cesium, the EPFL scientists led by Prof. Michael Saliba, made the first ever triple-cation perovskite mixture (Cs/MA/FA). The new films are more heat-stable and less affected by fluctuating surrounding variables such as temperature, solvent vapours or the heating protocol used for the device. But more importantly, they also show stabilised power-conversion efficiencies of 21.1% and outputs at 18% under operational conditions, even after 250 hours.

"This is an absolute breakthrough," said Saliba. "These properties are crucial for commercialising perovskite photovoltaics, especially since reproducibility and stability are the main requirements for cost-effective large-scale manufacturing of perovskite solar cells."

The study involved a collaboration of EPFL's Laboratory of Photonics and Interfaces, Laboratory of Photomolecular Science, Group for Molecular Engineering of Functional Materials and the Panasonic Corporation.

The project was funded by the European Union's Seventh Framework Programme for research, technological development and demonstration, the SNSF-NanoTera (SYNERGY) and the Swiss Federal Central, Office of Energy (SYNERGY), CCEM-CH, and the King Abdulaziz City for Science and Technology (KACST).