Researchers at Aalto University have developed a method for improving perovskite-based solar cells, that builds on previous breakthroughs improving the efficiency and longevity of such cells using printing methods (carbon back contact based perovskite solar cells or CPSCs). These findings make it possible to further enhance the efficiency of these types of solar cells.

In the new method, the perovskite solar cells were exposed to 40-degrees in a chamber where humidity was kept in the level of 70% (±5%). This kind of environment normally degrades the properties of perovskite solar cells. In this case, the treatment led to surprising growth of the perovskite crystals, which naturally absorb sunlight and generate electricity. “The photovoltaic performance was significantly enhanced, and the overall efficiency increased almost 45%,” say the researchers.

The team also examined the perovskites using a scanning electron microscopy (SEM). “The SEM images supported the previous observations obtained from the X-ray diffraction method analysis, which endorsed the gradual crystal growth over the period of exposure”.

The team also aimed to check if any chemical changes occurred in the perovskite crystal structure induced by the moisture generated by the thermo-humid environment. The researchers utilized Fourier transform infrared spectroscopy (FTIR). “The comparison between the fresh and exposed solar cells revealed almost no change in the chemical structure of the perovskite light absorbing layer, which endorses the successful implementation of this new treatment method,” they report.

The team at Aalto benefited from working with collaborators in Switzerland, the Solaronix company and the Swiss Federal Institute of Technology (EPFL) in Lausanne. “Solaronix provided the samples and EPFL researcher Dr Ibrahim Dar helped us in key processes that are critically required for the successful commercialization of this low cost solar cell technology,” says the team.