Layer‐by‐layer deposition of J‐aggregates and polyelectrolytes for electroluminescence applications: A spectroscopic study

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Abstract The self‐assembly method of layer‐by‐layer deposition of oppositely charged polyelectrolytes is used to insert J‐aggregates of the dye tetrachloro‐diethyl‐disulfobutyl‐benzimido‐carbocyanine (TDBC) into thin polymeric films. The J‐aggregates are characterized by a narrow absorption‐ and fluorescence band with its maximum at 590 nm, which is red‐shifted with respect to the monomeric transition at 515 nm. The dyes are either coadsorbed with the polyelectrolytes poly(allylamine hydrochloride (PAH) and poly(styrene sulfonate) (PSS), or alternately deposited with the precursor of poly(phenylene vinylene) (pre‐PPV). The optical properties of the aggregates are not changed significantly by the deposition process. The pre‐PPV/TDBC films are heated under vacuum to convert the PPV to its conjugated form. The resulting films can be used for the fabrication of light‐emitting devices. The optical properties such as fluorescence and electroluminescence are dominated by the J‐aggregates. The excitation energy of PPV is transferred to the dye aggregates with an efficiency of 100%. The electroluminescence is not very stable and shows a very slow turn‐on time. However, the combination of self‐assembled PPV/TDBC layers with a spin‐coated film of PPV results in stable electroluminescence emission under ambient conditions. In this case, light is emitted from both species, the PPV and the J‐aggregates, whereas the ratio of the two intensities strongly depends on temperature.

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