Photophysical and morphological properties of spin-coated and self-assembled carbazole derivative thin films

Abstract

In this work, single-layered, bi-layered and tri-layered poly(vinyl-carbazole) (PVK) thin films were produced by spin-coating and self-assembling techniques and their morphological and photophysical properties were determined by time-resolved fluorescence spectroscopy, atomic force microscopy (AFM) and fluorescence microscopy. The effect of distinct aggregates formed in thin films on their photophysical and morphological properties was determined, evidencing that procedure control is essential to determine PVK thin film application. It was found that sandwich excimers are dominant in self-assembled films, evidenced by longer fluorescence lifetimes and red-shifted emissions, while in spin-coated films, shorter fluorescence lifetimes evidenced more efficient non-radiative energy transfer. AFM showed that consecutive deposited layers result in more uniform, thinner films when produced by spin-coating, but showing aggregation heterogeneity as evidenced by fluorescence spectroscopy. Yet, self-assembled films are rough, heterogeneous and thicker, showing prevalence of less variety of aggregates. These are crucial findings to address PVK application.