MoS2 nanocavity could boost solar cells, optoelectronics and more

Engineers at the University at Buffalo, New York (US), have placed a single layer of the two-dimensional semiconductor molybdenum disulfide (MoS2) on top of an optical nanocavity made of aluminum oxide and aluminum. The nanocavity can increase the amount of light that this ultrathin semiconducting material absorbs, which could foster a new generation of more powerful and efficient thin-film solar panels, flexible optoelectronics, faster photodetectors for video cameras and more.

A nanocavity is an arrangement of mirrors that allows beams of light to circulate in closed paths. “These cavities help us build things like lasers and optical fibers used for communications,” says co-lead researcher Haomin Song, a PhD candidate in the lab lead by Qiaoqiang Gan, PhD, assistant professor of electrical engineering in Buffalo's School of Engineering and Applied Sciences. “We carefully designed an optical nanocavity, which is formed by a multi-layer structure of MoS2, alumina spacer and aluminum,” Song says. “Our collaborator, Dr. Zhiwen Liu’s group at the Pennsylvania State University, placed the single layer of MoS2 molecules on top of the pre-designed optical nanocavity. The MoS2 nanocavity could increase the amount of light that ultrathin semiconducting materials absorb. The enhanced absorption was verified by the stronger photoluminescence signal.”

The nanocavity could solve a major problem for energy-harvesting optoelectronic technologies, which is that these ultrathin semiconductors smaller, thinner devices require do not absorb light as well as conventional bulk semiconductors. “Therefore, there is an intrinsic tradeoff between the ultrathin semiconductors’ optical absorption capacity and their thickness. The nanocavity is a potential solution to this issue,” Gan says.

The results of the Gan team’s experiments are promising: The nanocavity absorbed nearly 70% of the laser they projected on it. “Its ability to absorb light and convert that light into available energy could ultimately help industry continue to more energy-efficient electronic devices,” Song projects.