Photo- and electroluminescence from hyperbranched phenylene vinylenes

We report photophysical and electroluminescence (EL) properties of three novel hyperbranched phenylene vinylenes (HPVs) with benzene as the core, 2,5-dimethyloxyl substituted phenylene vinylene as the connecting unit, and benzene, dimethylaniline, or pyridine as the terminal group, respectively. The absorption maxima of the HPVs blue-shift from solution to the films due to their twisted molecular conformation. The emission spectra in the films red-shift compared to those in solution, which may originate from interchain excimer species. The thin films of the HPVs exhibit pretty high photoluminescence (PL) quantum yields around 50.5-87.8%. Blue-green light-emitting electrochemical cells (LECs) based on the HPVs have been demonstrated with turn-on voltages of 2.5-2.6 V. The ac impedance measurements indicate the operation of the LECs corresponds to an electrochemical doping model. (C) 2003 Elsevier Science B.V. All rights reserved.