ZSW Develops Ecofriendly Coating For Perovskites

• ZSW replaced a toxic solvent DMF with an ecofriendly DMSO to achieve 16.7% efficiency for a small size perovskite solar cell
• While this efficiency is 0.2% lower than the efficiency reached with DMF, the research team believes it is scalable to larger production numbers
• They modified the film formation process using silicon oxide nanoparticles, improved the drying method and used blade coating method to deal with challenges posed due to the use of DMSO

Germany's Center for Solar Energy and Hydrogen Research Baden-Württemberg (ZSW) has reported achieving 16.7% efficiency for a 0.24 cm² perovskite solar cell coated with a single non-toxic solvent, dimethyl sulfoxide (DMSO) using a blade coating method, claiming it to be suitable for industrial applications.

Under current production processes used, perovskite precursors need to be dissolved in solvents to be applied in uniform layers to the substrate. The solvent most commonly used contains dimethylformamide (DMF) that's detrimental to health and the environment, but produces 0.2% higher efficiency for ZSW's perovskite solar cells.

The problem with DMSO that the team figured was that because of its high surface tension and viscosity, it leaves an uneven layer on the solar cell and makes it difficult to control the crystallization process. To deal with this, ZSW researchers modified the film formation process using a surfactant of silicon oxide nanoparticles, improved the drying method and deployed a blade coating method.

"It is scalable to larger production numbers and therefore suitable for industrial applications," explain the researchers, while adding that it is the spin-coating method that leads to higher efficiency for perovskite cells as compared to blade coating.

"These new research findings are an important milestone on the path to industrial production," said Head of the ZSW's Photovoltaics: Materials Research Department, Dr Jan-Philipp Becker. "Now we will further optimize the manufacturing process and produce larger modules."

Perovskites are interesting for the solar industry as these can be 'inexpensively made with ink', and also used as a thin film for a variety of applications where heavy conventional solar modules cannot be used, as vehicles, light industrial sheds, buildings, and these can also be deployed on plastic. Researchers all across the globe are working on various methods to improve their efficiency for large area solar cells that can be used for mass commercial use. ZSW's efforts are a step in this direction.

ZSW research has been published in the scientific journal ACS Applied Energy Materials with the title One-Step Blade Coating of Inverted Double-Cation Perovskite Solar Cells from a Green Precursor Solvent.