Fabrication of cyanine dye thin films grown by a layer-by-layer method

Abstract

We report the optical properties of the cyanine dye molecule thin film fabricated by a layer-by-layer method. While the absorbance and the film thickness increase with the dipping time, the use of a multilayer structure enables fabrication of the thin film without the creation of the molecule bundle that suppresses light scattering and the large absorbance obtained for the shorter dipping time. Exciton dynamics are studied by using a pump-probe technique; the signal shows two decay components in the multilayer sample that originates from the fast intramolecular relaxation and from the slow exciton relaxation. The temporal profiles show at the high signal-to-noise ratio. These results indicate that the thin film without the creation of the molecule bundle fabricated by the layer-by-layer method can be used for ultrafast all-optical switches.

Increase in exciton decay rate due to plane-to-plane interaction between cyanine thin films

“…All profiles consist of two components: a fast component is attributed to intramolecular decay, and a slow component is attributed to exciton decay. 39 Because the fast component observed in the PSA1411 thin film is slower than the temporal pulse shape, the fast component is a result of not the coherent artifact but the intramolecular decay. Both the intramolecular and exciton decay rates of the DTTCI molecules seem to be enhanced by stacking the DTTCI layer on the PSA1411 layer, which was not observed by stacking the layers of a single type molecule.…”

“…Both the intramolecular and exciton decay rates of the DTTCI molecules seem to be enhanced by stacking the DTTCI layer on the PSA1411 layer, which was not observed by stacking the layers of a single type molecule. 39 In order to evaluate these decay rates, fitting with double exponential function was performed as follows: where C 1 and C 2 are the intensities and k 1 and k 2 are the intramolecular and exciton decay rates, except in the D-P thin film. The evaluated k 1 and k 2 are listed in Table I.…”

“…[40][41][42] Previously, we reported fabrication of the LBL thin films with improved signal-to-noise ratio in pump-probe measurement. 39 The polymer layer consists of two layers of positively charged…”

“…In our previous study, we were able to fabricate high quality layer-by-layer (LBL) thin films, in which the exciton dynamics could be precisely measured. 39 Therefore, in this study, we clarify the mechanism of the increase in the exciton decay rate in the cyanine molecule thin films. While the exciton decay rate increases with different cyanine layers of the thin films, the rate for separation is almost constant.…”

“…39 At the beginning of sample fabrication, the adhesion layer of (PAA/PDDA) 3 was deposited to enhance the binding of PSA1411 molecules to the substrate, where the subscript indicates the number of pairs of PAA and PDDA layers. The bottom PSA1411 layer is adsorbed to the adhesion layer on the substrate with a dipping time of 4 min, followed by the adsorption of the top DTTCI layer with a dipping time of 10 s. The thicknesses of the DTTCI L D and PSA1411 L P layers were 10.7 nm and 3.8 nm, respectively.…”