Morphology-defined interaction of copper phthalocyanine with O2/H2O

Eric S. Muckley; Nicholas Miller; Christopher B. Jacobs; Thomas Gredig; Ilia N. Ivanov

doi:10.1117/1.JPE.6.045501

1 November 2016 Morphology-defined interaction of copper phthalocyanine with O₂/H₂O

Eric S. Muckley, Nicholas Miller, Christopher B. Jacobs, Thomas Gredig, Ilia N. Ivanov

Author Affiliations +

Journal of Photonics for Energy, Vol. 6, Issue 4, 045501 (November 2016). https://doi.org/10.1117/1.JPE.6.045501

Abstract

Copper phthalocyanine (CuPc) is an important hole transport layer for organic photovoltaics (OPVs), but interaction with ambient gas/vapor may lead to changes in its electronic properties and limit OPV device lifetimes. CuPc films of thickness 25 and 100 nm were grown by thermal sublimation at 25°C, 150°C, and 250°C in order to vary morphology. We measured electrical resistance and film mass in situ during exposure to controlled pulses of O₂ and H₂O vapor. CuPc films deposited at 250°C showed a factor of 5 higher uptake of O₂ as detected by a quartz crystal microbalance (QCM), possibly due to the formation of β-CuPc at T>200°C which allows higher O₂ mobility between stacked molecules. While weight-based measurements stabilize after ∼10 min of gas exposure, resistance response stabilizes over times >1 h, suggesting that mass change occurs by rapid adsorption at active surface sites whereas resistive response is dominated by slow diffusion of adsorbates into the bulk film. The 25 nm films exhibit higher resistive response than 100 nm films after an hour of O₂/H₂O exposure due to fast analyte diffusion down to the film/electrode interface. We found evidence of decoupling of CuPc from the gold-coated QCM crystal due to preferential adsorption of O₂/H₂O molecules on gold.

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Eric S. Muckley, Nicholas Miller, Christopher B. Jacobs, Thomas Gredig, and Ilia N. Ivanov "Morphology-defined interaction of copper phthalocyanine with O₂/H₂O," Journal of Photonics for Energy 6(4), 045501 (1 November 2016). https://doi.org/10.1117/1.JPE.6.045501

Published: 1 November 2016

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