A Simple Additive to Improve Perovskite Thin Films for Solar Cells

A KAUST team has discovered that thin films used in solar cells are more effective when simple chemicals called glycol ethers are incorporated to the film-forming mix.

Photovoltaic wafers developed for use in solar cells. The new perovskite thin films have improved structure and efficiency (© 2017 Frédéric Laquai)

This is an unexpected discovery. It yields more uniform thin films with improved structure and efficiency.

Esma Ugur, a PhD student, the KAUST Solar Center

Perovskites are materials possessing the same crystal structure as the naturally occurring perovskite calcium titanium oxide. A variety of metal halide perovskites are proving valuable for harvesting light energy that can then be used to produce electric current—the standard operating principle of a solar cell. The perovskites can be incorporated as a thin layer on top of conventional solar cells, because they can harvest the blue wavelengths of light to match the energy of red wavelengths trapped by traditional materials.

“Our aim was to improve the quality of perovskite thin films,” says Ugur. The team decided to incorporate glycol ethers to the manufacturing process as they knew these chemicals had earlier been used to help form layers of metal oxides.

By trying various glycol ether mixtures and conditions, the Researchers finally gained superior control over the formation of their perovskite thin films, by considerably enhancing the structure and arrangement of the perovskite grains. This improved the reproducibility and efficiency of the perovskites so that they performed more efficiently in solar cell applications.

The procedure also works at lower temperatures than substitutes, which is a vital factor in improving cost effectiveness.

So far, the team has only created small lab-scale devices. The following key challenge, explains Frédéric Laquai, who leads the KAUST Solar Center team, is to increase this to suit commercial applications. To realize this, they will need to discover ways to work around the instability of their perovskites.

We have several groups in the KAUST Solar Center working on that issue, and on other needs for future commercial development” says Laquai. He stresses that perovskites are a high priority research area for the Center, with probable applications other than merely solar cells. “Perovskites have many interesting optical and electronic properties, which may make them useful for applications that we have not even thought about,” he explains. Laquai also emphasizes the collaborative character of the projects at the KAUST Solar Center. He cites the ability to build on the know-how of experts from numerous different fields as key factors adding to their success.

Reference

Ugur, E., Sheikh, A.D., Munir, R., Khan, J. I., Barrit, D, Amassian, A. & Laquai, F. Improved morphology and efficiency of n-i-p planar perovskite solar cells by processing with glycol ether additives. ACS Energy Letters 2, 1960–1968 (2017).

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