Because the manufacturing of perovskite solar cells requires much less energy than similar silicon-based products, many people have regarded it as part of the green future of the solar industry. However, as perovskite batteries are getting closer to commercial production, the toxic substances in solvents have become a concern.
As we all know, the precursor material of perovskite solar cells must be dissolved in solvent in order to be evenly coated on the substrate. These solvents usually contain dimethylformamide (DMF), which is harmful to humans and the environment. In the actual production process, the treatment of this toxic solvent and strict safety measures will lead to the rise of battery production costs and hinder its commercialization process.
Therefore, manufacturers now urgently need a more mild non-toxic solvent. Scientists at the Baden Wuerttemberg solar and hydrogen energy research center (ZSW) have taken a big step towards this goal. Its researchers have developed a perovskite coating process using a single environmentally friendly solvent dimethyl sulfoxide (DMSO), which is non-toxic and suitable for use as an industrial solvent.
The researchers said that DMSO was not originally suitable for this coating process, because it is a solvent with high surface tension and viscosity, which will lead to the final inability to deposit evenly on the substrate. In addition, DMSO also makes it difficult to control the crystallization process, which often leads to the reduction of perovskite crystal and efficiency.
However, in the end, researchers overcome these problems by changing the formation and drying process of the film. They explained, “we used a surfactant made of silicon oxide nanoparticles to wrap perovskite solar cells and adjusted the drying process. With these two improvements, the process now produces a uniform layer with large crystals.”
The researchers made a prototype battery with a size of 0.24 square centimeters and achieved an efficiency of 16.7%. Compared with the 16.9% achieved by using DMF as solvent, this is a gratifying result.
The next challenge for the team will be to demonstrate the production of larger equipment through the same process. They said, “these new research findings are an important milestone on the road of industrial production. Now we will further optimize the manufacturing process and produce larger modules.”