Researchers at Linköping University, Sweden, have developed a stable high-conductivity polymer ink that could pave the way for printed electronics with high energy efficiency such as organic biosensors, solar cells, light-emitting diodes, transistors, and batteries.
The electrical properties of these conducting polymers can be tuned using a method known as "doping", where dopant molecules are added to the polymer to change its properties. Depending on the dopant, the doped polymer can conduct electricity by the motion of either negatively charged electrons (an "n-type" conductor), or positively charged holes (a "p-type" conductor).
While the most commonly used conducting polymer is the p-type, many electronic devices require a combination of p-types and n-types to function.
The researchers at Linköping University, together with colleagues in the US and South Korea, have developed a conductive n-type polymer ink, stable in air and at high temperatures – the formulation is known as BBL:PEI.
"This is a major advance that makes the next generation of printed electronic devices possible. The lack of a suitable n-type polymer has been like walking on one leg when designing functional electronic devices. We can now provide the second leg", said Simone Fabiano, senior lecturer in the Department of Science and Technology at Linköping University.
The new n-type material comes in the form of ink with ethanol as the solvent. The ink can be deposited by simply spraying the solution onto a surface, making organic electronic devices easier and cheaper to manufacture. The ink is also more eco-friendly than many other n-type organic conductors currently under development, which instead contain harmful solvents.
Fabiano believes that the technology is ready for routine use. "Large-scale production is already feasible, and we are thrilled to have come so far in a relatively short time. However, much remains to be done to adapt the ink to various technologies, and we need to learn more about the material.”