Literature Seminar Abstract

Pt(II) complexes have been extensively investigated as emitter dopants for organic light emitting diodes (OLEDs). A dopant greatly increases OLED efficiency due to the ability of the dopant to emit at room temperature from a triplet excited state. Triplet states represent the majority of excited states formed in OLED emitters during operation and cannot be utilized productively by traditional organic materials due to dominance of non-radiative decay pathways. Design of the dopant complex thus requires optimizing key photophysical parameters (e.g. maximizing emission quantum yield and minimizing the room temperature phosphorescence lifetime). The formation of excimers (excited dimers) is typically avoided due to its propensity to lower the emission quantum yield. However, Pinter et. al. have explored a family of emissive cyclometalated Pt(II) complexes in which addition of a N into the backbone of the N-heterocyclic carbene ligand leads to the unprecedented result that increasing the concentration of excimers formed leads to an increased emission quantum yield and decreased phosphorescence lifetime. In addition, the excimer formation could be controlled in solid-state thin films through selective wavelength irradiation and could be suppressed by incorporation of increasingly bulky auxiliary ligands. This discovery represents a design strategy that might improve existing excimer-based, single layer white light emitters.