Based on a news published at the “Chalmers” website, researchers from Chalmers University of Technology, Sweden, have discovered a simple new tweak that could double the efficiency of organic electronics. OLED-displays, plastic-based solar cells and bioelectronics are just some of the technologies that could benefit from their new discovery, which deals with “double-doped” polymers.
The majority of our everyday electronics are based on inorganic semiconductors, such as silicon. Crucial to their function is a process called doping, which involves weaving impurities into the semiconductor to enhance its electrical conductivity. It is this that allows various components in solar cells and LED screens to work.
For organic – that is, carbon-based – semiconductors, this doping process is similarly of extreme importance. Since the discovery of electrically conducting plastics and polymers, a field in which a Nobel Prize was awarded in 2000, research and development of organic electronics has accelerated quickly. OLED-displays are one example which are already on the market, for example in the latest generation of smartphones. Other applications have not yet been fully realised, due in part to the fact that organic semiconductors have so far not been efficient enough.
Doping in organic semiconductors operates through what is known as a redox reaction. This means that a dopant molecule receives an electron from the semiconductor, increasing the electrical 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 decreases. Currently, the efficiency limit of doped organic semiconductors has been determined by the fact that the dopant molecules have only been able to exchange one electron each.
But now, in an article in the scientific journal Nature Materials, Professor Christian Müller and his group, together with colleagues from seven other universities demonstrate that it is possible to move two electrons to every dopant molecule.
“Through this ‘double doping’ process, the semiconductor can therefore become twice as effective,” says David Kiefer, PhD student in the group and first author of the article.
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