Researchers from the University of Rochester have discovered a novel method to increase perovskites’ light conversion efficiency by 250%. It involves using a substrate of either a layer of metal or alternating layers of metal and dielectric material.

The finding was reported in Nature Photonics.

The Bill and Melinda Gates Foundation, the Army Research Office, and the National Science Foundation supported this research.

Perovskites have shown promise in recent years as a far less expensive, equally efficient replacement for silicon in solar cells and detectors.

Typically, researchers synthesize perovskites in a wet lab, and then apply the material as a film on a glass substrate and explore various applications.

However, the team here eliminates glass and attempted to tap into the potential of metal.

“No one else has come to this observation in perovskites…all of a sudden, we can put a metal platform under a perovskite, utterly changing the interaction of the electrons within the perovskite,” the researchers said.

In a solar cell, photons from sunlight need to interact with and excite electrons, causing the electrons to leave their atomic cores and generate an electrical current.

Ideally, the solar cell would use materials that are weak to pull the excited electrons back to the atomic cores and stop the electrical current.

The researchers demonstrated that such recombination could be substantially prevented by combining a perovskite material with either a layer of metal or a metamaterial substrate consisting of alternating layers of silver, a noble metal, and aluminum oxide, a dielectric.

The result was a significant reduction of electron recombination through “a lot of surprising physics,” lead author Guo said.

In effect, the metal layer served as a mirror, which created reversed images of electron-hole pairs, weakening the ability of the electrons to recombine with the holes.

The team was able to use a simple detector to observe the resulting 250% increase in the efficiency of light conversion.

‘Surprising Physics’ of Novel Perovskite-Metal Combination  

The researchers noted while metals may be the simplest material in nature, they can be made to acquire complex functions.

The team previously pioneered a range of technologies transforming simple metals to pitch black, super hydrophilic (water-attracting), or super hydrophobic (water-repellent). The enhanced metals have been used for solar energy absorption and water purification in their recent studies.

“A piece of metal can do just as much work as complex chemical engineering in a wet lab,” said Chunlei Guo, a professor of optics at the University of Rochester, adding that the new research may be particularly useful for future solar energy harvesting.”

Several challenges must be resolved before perovskites become practical for applications, especially their tendency to degrade relatively quickly.

Recently, researchers at the École Polytechnique fédérale de Lausanne and Sungkyunkwan University in South Korea identified the cause behind the degradation of perovskite solar cells and developed a technique to improve its stability.

Earlier in the month, researchers at the Helmholtz-Zentrum Berlin said that they have produced perovskite solar cells to achieve efficiencies of well above 24%, which are resistant to drop under rapid temperature fluctuations between -60 and +80 degrees Celsius over one hundred cycles.