Berlin 2012 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 13: Focus Session: Structural Ordering and Electronic Transport II (jointly with CPP)

HL 13.3: Vortrag

Montag, 26. März 2012, 15:45–16:00, ER 270

Aggregation in a High Mobility n-type Low Bandgap Copolymer: Implications on Morphology and Charge Transport — •Robert Steyrleuthner¹, Marcel Schubert¹, Ian Howard², Christian Schilling³, Bastian Klaumünzer⁴, Zhihua Chen⁵, Peter Saalfrank⁴, Frederique Laquai², Antonio Facchetti⁵, and Dieter Neher¹ — ¹University of Potsdam, Institute of Physics — ²MPI for Polymer Research, Mainz — ³Nanolytics GmbH, Potsdam — ⁴University of Potsdam, Institute of Chemistry — ⁵Polyera Corporation, Illinois

The prominent copolymer P(NDI2OD-T2) exhibits very high electron OFET mobility of 0.85 cm2/Vs. Recent X-ray studies on P(NDI2OD-T2) revealed an exceptional in-plane order with distinct pi-stacking of the NDI cores (Rivnay et al.) while GIXD and NEXAFS measurements suggested a significant fraction of amorphous content (Schuettfort et al.). By investigating steady state and time dependent UV-Vis absorption/fluorescence spectroscopy on solutions of P(NDI2OD-T2), we identified distinct absorbing species and assigned them to intrachain CT-excitons on disorderd chains and to interchain excitations on aggregated chains. These results were confirmed by DFT calculations on individual and stacked chains. Analytical ultracentrifugation showed that aggregation in solution proceeds via the collapse of individual polymer coils. The analysis of chain aggregation in solution allowed for the quantitative deconvolution of the thin film absorption, yielding the aggregate content. Finally we find that the vertical transport (electron-only devices) is largely affected by the layer crystallinity.