New research into the use of perovskites as a cheaper alternative to silicon in solar cells and detectors has demonstrated how to make them even more efficient. To achieve this, scientists at the University of Rochester and the Chinese Academy of Sciences devised a physics-based approach to synthesizing perovskites using a substrate of either a layer of metal or alternating layers of metal and dielectric material instead of glass.
With silicon remaining costly to mine and purify, many studies have explored improving perovskite efficiency through chemical engineering as an alternative. However, a pure physical approach has not so far been achieved until now. While the lab of Chunlei Guo has previously investigated pure physical/laser technologies that change simple metals to pitch black, water-attracting or water-repellent, here the team looked to assess whether it was possible to also enhance more complex materials such as perovskites through physical means.
The synthesis of perovskites is usually carried out in a wet lab before the material is applied as a film on a glass substrate. However, as reported in Nature Photonics [Jin Lee et al. Nat. Photon. (2023) DOI: 10.1038/s41566-022-01151-3],placing a metal platform under a perovskite was shown to completely alter the interaction of the electrons within the material, increasing its light conversion efficiency by up to 250%.
In solar cells, photons from sunlight have to interact with and excite electrons so that they leave their atomic cores and produce an electrical current. It would be useful if solar cells involved weak materials to pull the excited electrons back into the atomic cores and stop the electrical current. In this study, such recombination was shown to be mostly stopped by combining a perovskite with either a layer of metal or a metamaterial substrate consisting of alternating layers of silver, a noble metal, and aluminum oxide, which is a dielectric.
The metal layer acts as a mirror that creates reversed images of electron-hole pairs, weakening the ability of the excited electrons in the perovskite to recombine with their atomic cores, increasing the efficiency of the perovskite to harvest solar light. As Chunlei Guo told Materials Today, “Our approach can be used for any devices that can benefit from a longer exciton lifetime, including solar cells, photodetectors, and phototransistors.”
This physics-based approach to tailoring material properties could be applied to further enhance the performance of new perovskites, as well as other types of materials. It is hoped the study could also help bring about a new pathway for developing high-efficiency perovskite-based optoelectronic and photonic devices.
“Our approach can be used for any devices that can benefit from a longer exciton lifetime, including solar cells, photodetectors, and phototransistors.”Chunlei Guo
Perovskite sample with new substrate