The best solar cells today aren't very good at using infrared light. But a team of researchers are trying to devise cells able to more efficiently use this portion of the spectrum. Their work may eventually lead not just to better solar cells, but also to energy scavenging sensors better able to harvest waste heat than those available today.
The group has invalidated the most commonly used model to explain the behavior of a special class of materials called highly mismatched alloys. These alloys are still in the experimental stages of development and consist of elements that won't naturally mix together using conventional crystal growth techniques.
The researchers say mixing methods such as molecular beam epitaxy are useful for combining disparate elements. In one case, researchers used MBE to make nitrogen mix with gallium arsenide nitride to form a highly mismatched alloy that can tap into infrared radiation. They found that in some cases, the nitrogen atoms had clustered together, contrary to what the prevailing "band anti-crossing" model predicted.
Key to producing materials better able to convert light and heat into electricity is learning how to control the formation of these clusters, researchers say.
This research will be published in the Sept. 15 issue of Physical Review B. The paper is entitled "Nitrogen composition dependence of electron effective mass in gallium arsenide nitride."
Several of the authors hail from the University of Michigan which posted a news item on the paper: http://www.ns.umich.edu/htdocs/releases/story.php?id=7962
The paper itself is here: http://prb.aps.org/abstract/PRB/v82/i12/e125203