CPM Seminar

Structure and energetics of doped organic semiconductors

Ingo Salzmann

Department of Physics, Department of Chemistry & Biochemistry
Concordia University

Doping organic semiconductors (OSCs) for enabling new functionality and improving opto-electronic device performance is done by adding strong molecular acceptors as p-dopants to the OSC host. I will discuss the broad range of phenomena observed upon molecularly p-doping conjugated polymers (CPs) and molecules (COMs), where two different competing scenarios emerged [1,2]: (i) integer-charge transfer between OSC and dopant forming ion pairs (IPAs), and (ii), partial charge transfer with the emergence of OSC/dopant ground-state charge transfer complexes (CPXs). As prototypical representatives for these two scenarios, IPA formation in F4TCNQ-doped poly(3-hexylthiophene) (P3HT) is juxtaposed to CPX formation found for its parent oligomer, and the respective doping-induced modification of the density of states (DOS) is generally discussed and experimentally assessed by photoelectron spectroscopy. I will further focus on the determination of the thin-film structure of COMs/CPs and the modification thereof by molecular doping. Correlating Grazing-incidence X-ray diffraction with infrared spectroscopy for thermally annealed films finally provides insight into the complex growth behavior of p-doped P3HT.

[1] I. Salzmann et al., Acc. Chem. Res. 49, 370 (2016)
[2] H. M�ndez et al., Nature Commun. 6, 8560 (2015)