Carbon-based organic semiconductors could soon play a major role in electronics and solar energy conversion.
Semiconductors, usually made of silicon, are essential to all modern electronics and can be found in everything from smartphones to televisions.
Semiconductors are somewhere between a conductor and an insulator. They don’t work as a true insulator like glass, nor do they have the same conductive strengths as metal, hence the name semi.
Doping is required to increase the conductive properties of a semiconductor. Doping is a process where chemicals or impurities are added to the semiconductor which then changes the electrical behavior of the semiconductor.
A team of researchers from Princeton University, the Georgia Institute of Technology and Humboldt University in Berlin have found a way to increase the conductivity of organic semiconductors with doping.
“Organic semiconductors are ideal materials for the fabrication of mechanically flexible devices with energy-saving low-temperature processes,” said Xin Lin, one of the researchers. “One of their major disadvantages has been their relatively poor electrical conductivity. In some applications, this can lead to difficulties and inefficient devices. We are working on new ways to improve the electrical properties of these organic semiconductors.”
For the study, the researchers developed a new type of dopant which drastically improves the conductivity of organic semiconductors.
The dopant is a ruthenium-containing compound and a reducing agent. It adds electrons to the semiconductor. The results show that the ruthenium compound dopant increases the conductivity of organic semiconductors nearly one million times its original value.
For the compound to work with organic semiconductors, the research team had to figure out how to break apart the ruthenium. The ruthenium compound is a dimer, and it contains two identical molecules which are connected by a chemical bond.
The researchers examined different possibilities for breaking the compound’s molecules apart in order for it to work as a dopant, eventually finding that when exposed to ultraviolet light the dopant increased the conductive properties by almost 100,000 times.
Even when the UV light was turned off, the dopant still worked with the organic semiconductors.
“Once the light is turned off, you might expect the reverse reaction to occur and the increased conductivity to disappear. However, that is not the case,” said Seth Marder, one of the leaders in the development of the new dopant. “The light activates the system more, which leads to more light production and ore activation until the system is fully activated.”
This discovery is a breakthrough for semiconductors and increasing the conductivity of organic semiconductors.