New technique to improve titanium dioxide films in dye‐sensitized solar cells

Researchers from Delft University of Technology have developed a new manufacturing process that could facilitate the eventual production of stable, high-performance perovskite solar cells.

The process, described in Characterization of Enzymatically Synthesized Titania Thin Films Using Positron Annihilation Spectroscopy Reveals Low‐Cost Approach for Organic/Inorganic Photovoltaic Cells – a study that was recently published in Advanced Sustainable Systems – is related to the production of the titanium dioxide thin films that are used for some PV cell technologies.

Papaya power

The researchers claim that the new technique facilitates the production of highly porous titanium dioxide layers by using an enzyme known as papain, which is naturally found in the papaya fruit. They bought papain fruit extract powder from Shaanxi Sangherb Bio‐Tech. The porous nature of the films is key to gaining access to a large surface area and achieving stronger performance.

The titanium dioxide films were immersed for 24 hours in juice to enable the adhesion of the dye molecules. “The immersion was carried out at room temperature in low‐light conditions to prevent destabilization of the dye,” the researchers said. “Afterward the dye-coated slide was rinsed with ethanol and dried with nitrogen gas to ensure that no water was left in the film.”

According to researcher Duncan McMillan, the gentle heating of the films in a regular home oven resulted in the evaporation of most of the organic material, leaving behind porous titania films. Traditional methods usually need a powerful vacuum or equipment to heat the films to 600° C.

Devices for windows

This new technique, according to the research group, could lead to the production of more efficient PV cells that could be integrated into windows.

“The enzyme papain was used successfully in a room temperature dip-coating procedure to synthesize multilayered porous titania/papain thin films, providing a straightforward, low-cost, and ecological method to produce titania thin films with tunable thickness,” the researchers concluded.

Last year, Japanese researchers used anatase and brookite, which are two different variants of titanium dioxide, to improve the efficiency of perovskite-based solar cells. Another group of Japanese researchers recently used tin dioxide (SnO₂) instead of the more commonly used titanium dioxide, to produce a perovskite solar cell.

In March 2019, a group of scientists from the US Department of Energy’s Argonne National Laboratory published findings on the replacement of titanium dioxide in the production of solar cells.