RESEARCH: New doping method could boost the performance of organic semiconductors
Organic semiconductors are carbon-based materials that can conduct electricity, and can be used for flexible, lightweight and potentially low-cost electronic devices. While the technology is promising, performance challenges remain.
Electric conductivity requires doping, a process of adding mobile electrical charges to the material. Conventional chemical dopants eventually reach a limit, restricting how many charges they can create.
In a recent study published in the journal Nature Materials, researchers at Concordia, the Institut national de la recherche scientifique (INRS) and York University outlined a way around that limit. Their research shows that allowing a chemical dopant to break down after transferring an electron can keep the doping process going, producing much higher concentrations of electrical charges.
The researchers call the process “degradation-assisted doping” (DAD). To understand how it works, they combined computer simulations with laboratory experiments using the organic semiconductor P3HT and a chemical compound called tris(pentafluorophenyl)borane, or BCF.
They used several techniques, including nuclear magnetic resonance, optical spectroscopy, electron paramagnetic resonance and calorimetry, to track what happened after BCF transferred an electron to P3HT. Computer modelling was used to examine the chemical reactions involved.
The results showed that BCF breaks down after accepting an electron, removing its reaction products from the process and allowing additional electrons to be transferred. The researchers found that the new method can create up to 100 times more mobile electrical charges in the semiconductor than conventional doping, potentially making the material much more conductive. BCF also produced higher conductivity in P3HT than other commonly used dopants.
The authors believe the findings establish DAD as a new strategy for improving the performance of organic semiconductors and could help researchers design more efficient materials for flexible electronics, optoelectronic devices and thermoelectric technologies.
The study was jointly led by Melissa Berteau-Rainville, PhD 26 (Energy and Materials Science), INRS, and Ingo Salzmann, an associate professor in Concordia’s Departments of Physics and Chemistry and Biochemistry. Berteau-Rainville conducted her doctoral research under the co-supervision of Salzmann and Emanuele Orgiu, professor at INRS. The work also involved key collaborations with researchers at York University (Thomas Baumgartner, professor; Christopher Caputo, assistant professor, and Taylor Cosby) and INRS.
The research was supported by the Natural Sciences and Engineering Research Council of Canada, the Fonds de recherche du Québec – Nature et technologies, Concordia University and the Canada Research Chairs program. Additional support came from Calcul Québec and the Digital Research Alliance of Canada.
Read the paper: “Degradation-assisted doping of organic semiconductors enabled by Lewis acids”