Local spatial distribution of J-aggregates in molecularly oriented bisazo-dye thin films

The spatial distribution of partially grown J-aggregates in films of oriented linear bisazo-dye molecules is analysed using polarised optical microscopy (POM), atomic force microscopy (AFM), and hyperspectral imaging. By depositing the bisazo dye onto a poly(tetrafluoroethylene) alignment layer, an oriented thin film containing highly oriented J-aggregates with a dichroic ratio exceeding 12 is prepared. AFM and POM using monochromatic light in the same area of the thin film reveal that the J-aggregates are locally formed and have a distribution different from that of the crystalline phase and grains. Furthermore, local spectral analysis of the film using a hyperspectral camera validates the local formation of J-aggregates. These results provide new insights into the formation process and control of J-aggregates, which are crucial for their potential applications in optoelectronics. LAY DESCRIPTION: Polarised optical microscopy (POM) combined with atomic force microscopy (AFM) enables visualisation of submicron-sized grains and reveals that the J-aggregate-containing phases (JCP) are mainly localised on the surface and sides of the grains.