Research from the Chilmer University of Technology, Sweden, has made a discovery that could double the efficiency of organic electronics, which could benefit OLED-displays, plastic-based solar cells, and electro-electronics and other technologies.
Most everyday electronics are based on inorganic semiconductors such as silicon. "Doping", including weaving impurities in the semiconductor to improve its electrical conductivity, is critical to its operation and allows various components in solar cells and LED screens to operate.
This process is also important in organic, carbon-based semiconductors. Organic semiconductor doping operates through what is known as a redox reaction. This means that a dopant molecule receives an electron from the semiconductor, increasing the conductivity of the semiconductor.
The more dopant molecules that the semiconductor can react with, the higher the conductivity – at least up to a certain limit, after which the conductivity will drop. Meanwhile, the efficiency limit of doped organic semiconductors is determined by the fact that dopant molecules have been able to exchange only one electron each.
Recently published in the scientific journal Nature materialsProfessor Christian Muller and his group of Chalmers University of Technology, along with colleagues from seven other universities, prove that it is possible to move two electrons to each dopant molecule.
"By the double doping process, the semiconductor could then be twice as effective," said David Kiefer, a PhD student working with the research group.
"The entire research field is totally focused on students, who only allow one redox reaction per molecule," Muller said.
"We chose to look for a different type of polymer, with lower ionization energy. We saw that this material allowed the transfer of two electrons to the dopant molecules. It's actually very simple."
The reveal could allow for further improvements to technologies that are currently not competitive enough to market. One problem is that polymers simply do not perform well enough, and thus making these doping techniques more efficient has long been a focus for achieving better polymerized electronics. Now, the doubling of the conductivity of polymers, while using only the same amount of dopant material over the same surface area as before, could represent the tipping point needed to allow some emerging technologies to commercialize.
"With OLED displays, the development has come far enough that they are already on the market, but for other technologies to succeed and make it to the market something extra is needed," Muller said.
"With organic solar cells, for example, or electronic circuits built of organic material, we need the ability to deposit certain components to the same extent as silicon based electronics. Our approach is a step in the right direction."