| Work Detail |
A team at Colorado State University in the United States has proposed making thin-film solar cells from molybdenum disulfide, which is abundant in nature.
Most solar panels are made from silicon, a well-proven semiconductor material that is not without its limitations. For example, silicon loses up to 40% of the energy it collects from sunlight as waste heat. Colorado State University researchers are studying radical new ways to improve solar energy and offer more options for the future.
Chemists at Colorado State University propose to make solar cells using an abundantly available natural material called molybdenum disulfide. Using a combination of photoelectrochemical and spectroscopic techniques, the researchers carried out a series of experiments that demonstrated that extremely thin films of molybdenum disulfide exhibit unprecedented charge carrier properties that could one day dramatically improve solar technologies.
The experiments were led by chemistry doctoral student Rachelle Austin and postdoctoral researcher Yusef Farah. Austin works jointly in the labs of Justin Sambur, an associate professor in the Department of Chemistry, and Amber Krummel, an associate professor in the same department. Farah is a former PhD student in Krummels lab. His paper, “ Hot carrier extraction from 2D semiconductor photoelectrodes ,” is published in the Proceedings of the National Academy of Sciences.
Samburs lab became interested in molybdenum sulfide as a possible alternative solar material based on preliminary data on its ability to absorb light even when it is only three atoms thick, Austin explained.
The collaboration took advantage of Samburs knowledge of solar energy conversion with nanoscale materials and Krummels knowledge of ultrafast laser spectroscopy, which helped them understand the structure and behavior of different materials.
Krummels lab has a pump-probe ultrafast transient absorption spectrometer that can very accurately measure the sequential energy states of individual electrons when excited with a laser pulse. Experiments with this spectrometer can provide snapshots of how charges flow in a system.
Austin created a photoelectrochemical cell using a single atomic layer of molybdenum sulfide, and she and Farah used the pump-probe laser to track the cooling of the electrons as they moved through the material. The result was astonishingly efficient light-to-energy conversion. More importantly, laser spectroscopy experiments allowed them to show why this highly efficient conversion was possible.
What they found was that the material could convert light into energy so well because its crystalline structure allowed it to draw and exploit energy from so-called hot carriers, highly energetic electrons that are briefly excited from their ground state when they receive enough visible light. . The researchers found that, in their photoelectrochemical cell, the energy from these hot carriers was immediately converted to photocurrent, rather than lost as heat, providing an advantage over conventional silicon solar cells.
“This work paves the way for how to design reactors containing these nanoscale materials for large-scale, efficient hydrogen production,” Sambur said.
The project was supported by Professor Andrés Montoya-Castillo and Dr. Thomas Sayer, from the University of Colorado Boulder, who provided theoretical chemistry and computational modeling to help explain and verify the experimental data.
“The discovery required a team science approach that brought together a lot of different knowledge in computational, analytical, and physical chemistry,” Krummel explained. |
