SKM 2023 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 17: Poster Session I

CPP 17.5: Poster

Monday, March 27, 2023, 18:00–20:00, P3

Understanding the Double Doping of Organic Semiconductors Via State Energy Renormalization upon Charging — •Ross Warren¹, Eunkyung Cho², Hong Li², Jean-Luc Bredas², and Norbert Koch^1,3 — ¹Institut für Physik & IRIS Adlershof, Humboldt-Universität zu Berlin, 12489 Berlin, Germany — ²Department of Chemistry and Biochemistry, The University of Arizona, Tucson, Arizona 85721-0088, United States — ³Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, 12489 Berlin, Germany

The double ionisation of dopants is a recent experimental observation that allows the doping efficiency to rise above 100%. This is exciting because high conductivities can be achieved with fewer dopant molecules, meaning less disruption to the resulting film's microstructure. However, the current models of doped organic semiconductors based on Fermi-Dirac statistics fail to explain the double ionization of dopants and also the analogous situation of bipolaron formation on a host polymer. Here, we address this shortcoming by considering the renormalization of the state energies upon electron transfer between host and p-dopant. We vary the model parameters - the reorganization energy and evolutions of ionization energies and electron affinities upon charging - and plot the fractions of doubly ionized, singly ionized, and neutral species. We find good agreement with experiment. Finally, we suggest that the state energy renormalization upon charging is the key parameter to be minimized for double ionization of dopants or maximized to avoid formation of bipolarons on the host.