Photophysical study of triplet state in pi-conjugated donor-acceptor systems in platinum (II)-carbene derivative chromophers for phosphorescent OLED application

Abstract

This project aims at investigating excited state properties in donor-acceptor pi-conjugated chromophores, more precisely platinum (II) carbene-derivative, with emphasis on understanding intersystem crossing dynamics and triplet state properties. The materials will also be tested on optoelectronic devices such as organic light emitting diodes (OLED). Therefore, one of the aspects of this project will be to study the electroluminescent properties of these new materials and to compare them with the photoluminescent properties. We will start the studies with several complexes in which N-heterocyclic carbene (NHC = N-heterocyclic carbene) and an arylacetylene ligands will be varied, with 5- and 6-membered ring heterocycles for the arylene units (examples are shown in Scheme 1 of the project). The project also includes time-resolved spectroscopy on timescales ranging from femtoseconds to microseconds and over the near-ultraviolet to near-infrared spectral range. The goal of the spectroscopic investigations is to understand the dynamics and electronic structure of excited states in donor-acceptor and heavy atom modified donor-acceptor systems. Heavy atom substitution, using platinum (II), was chosen to enhance spin-orbit coupling to give rise to increased intersystem crossing and triplet radiative decay (phosphorescence) yields. Much is known regarding triplet states in organic and organometallic chromophores; however, there has been little previous work on triplet states in chromophores where there is a strong donor-acceptor (charge transfer) interaction. (AU)