Dresden 2017 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 22: Organic Electronics and Photovoltaics II: Doping

HL 22.1: Hauptvortrag

Montag, 20. März 2017, 15:00–15:30, ZEU 260

Molecular Electrical Doping of Organic Semiconductors — •Ingo Salzmann — Humboldt Universität zu Berlin, Berlin, Germany

In contrast to inorganic semiconductors, the potential of doping organic semiconductors (OSCs) for enabling new functionality and improving opto-electronic device performance has only recently been established. Here, the broad range of phenomena observed upon molecularly doping conjugated polymers (CPs) and molecules (COMs) is discussed, from which, finally, two different competing scenarios emerge [1]: (i) the formation of both OSC and dopant ions through integer-charge transfer, i.e., an ion pair (IPA), and (ii), the emergence of OSC/dopant ground-state charge transfer complexes (CPXs). In particular, the doping of poly(3-hexylthiophene) (P3HT) will be juxtaposed with that of quaterthiophene (4T) where, for both systems, an increase in thin-film conductivity by several orders of magnitude is observed. The underlying doping mechanisms at work are, however, fundamentally different [2]: IPA formation occurs for the polymer while CPX formation is found for the chemically and structurally similar oligomer. For both cases (i) and (ii), the doping-induced modification of the OSC density of states (DOS) is generally discussed for both p- and n-doping and its Fermi-Dirac occupation is modelled by numerical simulations. Therefrom finally emerges that engineering the DOS of doped OSCs, the occupation of which ultimately determines the doping efficiency, represents a key challenge in dopant design.

[1] I. Salzmann et al., Acc. Chem. Res. 49, 370 (2016)

[2] H. Méndez et al., Nature Commun. 6, 8560 (2015)