Efficient Singlet Energy Migration in Amorphous Copolymer Film Having No Excimer Forming Site: Poly[2‐(9‐carbazolyl)ethyl methacrylate‐co‐methyl methacrylate]

Energy Transfer / Fluorescence / Polymers Singlet energy migration in the solid state for the homopolymer of 2‐(9‐carbazolyl)ethyl methacrylate and the copolymers with methyl methacrylate was investigated using perylene as an acceptor molecule. In this system, the carbazole (Cz) chromophore is dispersed uniformly even in the homopolymer and a deep trap is not formed. The fluorescence spectra and their decays were measured for these samples and the energy migration was analyzed on the basis of three models, i.e., random hopping model, Smoluchowski diffusion model, and Yokota‐Tanimoto (Y‐T) Padé model. Among these models, the Y‐T Padé model gave the most reliable diffusion coefficient. The diffusion coefficient was obtained in a wide range of carbazole concentrations from 0.14 to 4.4 mol/l and we obtained the following conclusions. 1. The energy diffusion coefficient D is proportional to [Cz]4/3 as predicted from the Förster mechanism even for the samples of Cz concentration higher than 1 mol/l. 2. At a low temperature, the energy migration rate becomes slow owing to shallow traps. The activation energy in a low temperature region is about 4 kJ/mol. 3. Fast energy migration (D = 2.0·10−4 cm2/s) was found for the polymers whose concentration of Cz‐chromophore is high, but do not form excimer.