Electrochromism in ytterbium bisphthalocyanine-(stearic acid or cadmium stearate) films deposited by the Langmuir-Blodgett technique

Abstract

The monolayer and deposition behaviour of a series of ytterbium bisphthalocyanine and stearic acid mixtures deposited from both pure water and 10 −4M Cd 2+ subphases was investigated. Lower than expected average area per molecule values suggest that the bisphthalocyanine is forming aggregates within the stearic acid and cadmium stearate matrices. Relative to a pure ytterbium bisphthalocyanine monolayer the mixed materials were much more stable with respect to collapse, this being especially true on a Cd 2+ subphase. Transfer ratios of unity were obtained for all mixtures, yielding electrochromic films for all but the most dilute films of the bisphthalocyanine. Analysis by X-ray diffraction gave a layer spacing of 50 Å for films containing cadmium stearate and a spacing of 42 Å for films containing stearic acid. On incorporation into an electrolytic cell, the latter films produced a layer spacing of 50 Å. A mixture of 1:5 ytterbium bisphthalocyanine:cadmium stearate forms an excellent material for the fabrication of electrochromic Langmuir-Blodgett films, giving uniformly deposited bilayers by Y-type deposition.