Double Doping of Semiconducting Polymers

Research Project, 2018 – 2021

Molecular doping is an important and widely used process that allows to control the electrical properties of organic semiconductors. One aspect that requires significant improvement is the doping efficiency, i.e. the amount of charges that are generated per dopant molecule added to the semiconductor host. Monomer molecular dopants are thought to give rise to a maximum of one charge in case of complete charge transfer, which corresponds to a doping efficiency of 100%. Initial results indicate that one of the most widely studied p-dopants can form dianions upon doping of polar polythiophenes, i.e. two charges are generated per dopant molecule, which translates into a maximum doping efficiency of 200%. In this project we will study this new type of double doping in detail, by addressing four central research questions:1) How does the nanostructure impact dianion formation?2) How does the energetic driving force and dielectric constant influence dianion formation? 3) Is double doping a generic concept?4) Can blending with a high-dielectric constant matrix enhance dianion formation?The project will run over four years, and combine spectroscopy, structural and electrical characterisation. To accelerate progress and maximise timeliness and impact, two postdocs will be active in the project during year 1-2 and 3-4, respectively. The knowledge gained will provide us with a complete picture of double doping, and ultimately benefit many emerging applications of organic semiconductors.