University of Michigan researchers have developed a new equation that describes the current–voltage relationship at the junctions of organic semiconductors. Organic semiconductors present special challenges for researchers because they are more disordered than their inorganic counterparts. But they could enable advanced solar cells, thin and intense organic light-emitting diode displays and high-efficiency lighting.
“The field of organic semiconductor research is still in its infancy. We’re not making complicated circuits with them yet, but in order to do that someday, we need to know the precise relationship of current and voltage. Our new equation gives us fundamental insights into how charge moves in this class of materials. From my perspective, it’s a very significant advance,” says Steve Forrest, the William Gould Dow Collegiate Professor of Electrical Engineering and U-M vice president for research.
According to a University of Michigan press release, the equation could have the same impact on solar cell development as the Shockley equation had on computers. Developed in 1949 by William Shockley, the inventor of the transistor, the Shockley equation describes the relationship between electric current and voltage in inorganic semiconductors such as silicon.
About six years ago, researchers in Forrest’s lab realized that they could use Shockley’s equation to describe the current/voltage relationship in their organic solar cells to a degree. Many physicists and engineers used the Shockley equation for organic semiconductors even though it didn’t describe the physics perfectly. The new equation does.
“People have been investigating organic semiconductors for 70 or 80 years, but we’re just entering the world of applications,” Forrest said. “This work will help advance the field forward.”
Two papers describing the work are published in the current edition of Physical Review B.