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Issue 20, 2015
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Ultrafast charge transfer in solid-state films of pristine cyanine borate and blends with fullerene

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Abstract

Photoinduced electron transfer in light-absorbing materials is the first step towards charge separation and extraction in small molecule-based organic solar cells. The excited state dynamics of the cyanine dye cation Cy3 paired with a tetraphenylborate counter-anion (Cy3-B) was studied in pristine solid-state films of the dye and in blends with the electron acceptor material PCBM. Here we show that photoexcited Cy3-B in pure films undergoes intra-ion pair reductive quenching on the picosecond time scale, while in blends with PCBM sub-picosecond formation of the Cy3 oxidized species is observed upon electron injection from the dye excited state into the fullerene. Kinetic competition between light-induced electron- and hole transfer processes strongly depends on the PCBM content in the blends. A high PCBM loading produces a fully intermixed phase, where the cyanine oxidized states appear on ultrashort (<160 fs) time scales. Lower PCBM contents, in contrast, lead to a Cy3-B segregated phase on top of the intermixed phase and slower excited state quenching. These findings show that the phase morphology indeed controls to a large extent the efficiency of primary photoinduced charge separation, on which small molecule-based organic photovoltaic cells rely.

Graphical abstract: Ultrafast charge transfer in solid-state films of pristine cyanine borate and blends with fullerene

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Supplementary files

Article information


Submitted
30 Jan 2015
Accepted
13 Apr 2015
First published
15 Apr 2015

J. Mater. Chem. A, 2015,3, 10935-10941
Article type
Paper
Author version available

Ultrafast charge transfer in solid-state films of pristine cyanine borate and blends with fullerene

J. De Jonghe-Risse, J. Heier, F. Nüesch and Jacques-E. Moser, J. Mater. Chem. A, 2015, 3, 10935
DOI: 10.1039/C5TA00784D

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