Okinawa Institute of Science and Technology Graduate University (OIST) Energy Materials and Surface Sciences Unit researchers led by Prof. Yabing Qi, have developed solar cells using a new perovskite material that is stable, efficient and relatively cheap to produce that may pave the way for their use in the solar cells of tomorrow.

Perovskite solar cells have not yet been produced on a commercial scale. Currently, the OIST Energy Materials and Surface Sciences Unit’s new perovskite solar cells are small enough for Dr. Liu to hold them in the palm of his hand. Image Credit: Okinawa Institute of Science and Technology Graduate University Energy Materials and Surface Sciences Unit. Click image for the largest view.

Their work has been published in Advanced Energy Materials. Postdoctoral scholars Dr. Jia Liang and Dr. Zonghao Liu made major contributions to this work.

The new perovskite material has several key features. First, it is completely inorganic – an important shift, because organic components are usually not thermostable and degrade under heat. Since solar cells can get very hot in the sun, heat stability is crucial. By replacing the organic parts with inorganic materials, the researchers made the perovskite solar cells much more stable.

Dr. Zonghao Liu, an author on the paper said, “The solar cells are almost unchanged after exposure to light for 300 hours.”

All-inorganic perovskite solar cells developed so far tend to have lower light absorption than organic-inorganic hybrids. This is where the second feature comes in: The OIST researchers doped their new cells with manganese in order to improve their performance. Manganese changes the crystal structure of the material, boosting its light harvesting capacity.

“Just like when you add salt to a dish to change its flavor, when we add manganese, it changes the properties of the solar cell,” said Liu.

Thirdly, in these solar cells, the electrodes that transport current between the solar cells and external wires are made of carbon, rather than of the usual gold. Such electrodes are significantly cheaper and easier to produce, in part because they can be printed directly onto the solar cells. Fabricating gold electrodes, on the other hand, requires high temperatures and specialist equipment such as a vacuum chamber.

There are still a number of challenges to overcome before perovskite solar cells become as commercially viable as silicon solar cells. For example, while perovskite solar cells can last for one or two years, silicon solar cells can work for 20 years.

Qi and his colleagues continue to work on these new cells’ efficiency and durability, and are also developing the process of fabricating them on a commercial scale. Given how quickly the technology has developed since the first perovskite solar cell was reported in 2009, the future for these new cells looks bright.

The university press release has an pretty well done brief background on perovskite cells. Some of the edited best follows.

Scientists have been working on an alternative to silicon solar cells that are made from perovskite structures. True perovskite, a mineral found in the earth, is composed of calcium, titanium and oxygen in a specific molecular arrangement. Materials with that same crystal structure are called perovskite structures.

Perovskite structures work well as the light-harvesting active layer of a solar cell because they absorb light efficiently but are much cheaper than silicon. They can also be integrated into devices using relatively simple equipment. For instance, they can be dissolved in solvent and spray coated directly onto the substrate.

Materials made from perovskite structures could potentially revolutionize solar cell devices, but they have a severe drawback: they are often very unstable, deteriorating on exposure to heat. This has hindered their commercial potential.

It looks like the Okinawans have make a great crack in the perovskite conundrum. Three hundred hours with almost unchanged stability is a huge improvement from immediate degrading.

A job well done indeed and more even more rewarding work to go.


Comments

1 Comment so far

  1. BESTONSORTING on May 9, 2018 6:06 AM

    So look forwarding to this technology being used commercially. It surely can change human’s life and the world in the future.

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