A recent study by researchers at the University of Rochester and the Chinese Academy of Sciences suggests that perovskites —a family of materials nicknamed for their crystalline structure— may become far more efficient than silicon in solar cells and detectors.
In a paper published in the journal Nature Photonics, the researchers propose a novel, physics-based approach to synthesize perovskites, instead of going the usual way and doing it in a wet lab, and then applying the material as a film on a glass substrate to explore various applications.
By using a substrate of either a layer of metal or alternating layers of metal and dielectric material—rather than glass— the scientists found they could increase the perovskite’s light conversion efficiency by 250%.
“No one else has come to this observation in perovskites,” lead author Chunlei Guo said in a media statement. “All of a sudden, we can put a metal platform under a perovskite, utterly changing the interaction of the electrons within the perovskite. Thus, we use a physical method to engineer that interaction.”
According to Guo, metals are probably the simplest materials in nature, but they can be made to acquire complex functions. His lab has pioneered a range of technologies transforming simple metals to pitch black, superhydrophilic (water-attracting), or superhydrophobic (water-repellent). The enhanced metals have been used for solar energy absorption and water purification in their recent studies.
In this new paper, instead of presenting a way to enhance metals themselves, the Guo Lab demonstrates how to use metals to enhance the efficiency of perovskites.
“A piece of metal can do just as much work as complex chemical engineering in a wet lab,” he said, adding that the new research may be particularly useful for future solar energy harvesting.
Guo pointed out that 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.
His lab 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,” according to Guo. In effect, the metal layer serves as a mirror, which creates reversed images of electron-hole pairs, weakening the ability of the electrons to recombine with the holes.
The lab was able to use a simple detector to observe the resulting 250% increase in the efficiency of light conversion.
The researcher and his team noted that, despite the promising results, several challenges must be resolved before perovskites become practical for applications, especially their tendency to degrade relatively quickly. Currently, researchers are racing to find new, more stable perovskite materials.
“As new perovskites emerge, we can then use our physics-based method to further enhance their performance,” Guo said.
