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Effect of thermal annealing on exciton diffusion in a diketopyrrolopyrrole derivative
Oleksandr V Mikhnenko1, Jason Lin, Ying Shu
1Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh, The Netherlands. alex@mikhnenko.com
Abstract:
We show that the method we have developed for measuring the singlet exciton diffusion length in blends with [6,6]-phenyl-C(61)-butyric acid methyl ester (PCBM) can be applied not only to polymeric materials, but also to small molecule organic semiconductors. Small organic molecules have a large potential for molecular re-organization upon thermal annealing. Here we show that the exciton diffusion length is decreased upon annealing from 9 to 3 nm in a thin film of a diketopyrrolopyrrole derivative. Such a variation is attributed to exciton delocalization effects in the crystalline domains that are formed during the annealing process as well as to the exciton quenching at grain boundaries.
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