Investigation of luminescent zinc and copper complexes as emitters in organic light emitting diodes (OLEDs)

Abstract

This thesis investigates a range of dinuclear zinc(II), copper(I) bis-imine, and copper(I) NHC complexes as emitters within OLEDs. The syntheses and photophysical properties of seven dinuclear zinc(II) disalphen macrocycles are described in Chapter 2. Five are weakly luminescent in solution (λem = 531 – 597 nm, PLQE < 1 %), moderately luminescent in the solid state (λem = 569 – 630 nm, PLQE = 1 – 5 %), and display aggregation induced enhanced emission (AIEE), however, are unsuitable candidates for OLEDs due to their low PLQE values. The syntheses and photophysical properties of eight dinuclear zinc(II) bis-salphens and one mononuclear zinc(II) salphen complex are described in Chapter 3. The complexes are moderately luminescent in solution (λem = 531 – 700 nm, PLQE = 2 – 27 %), and show weaker emission in the solid state (λem = 584 – 625 nm, PLQE < 1 – 4 %). Significant colour tuning (green to red emission) is reported across the dinuclear complexes. Two dinuclear zinc(II) bis-salphens are used as emitters in three OLED devices (up to 1.1 cd/A and 0.35 lm/W). A study of the solid state emission of copper(I) bis-imines and copper(I) NHCs is presented in Chapter 4. The emission from three copper(I) NHCs is further investigated (λem = 441 – 509 nm, PLQE = 3 – 45 %), and one displays bright blue emission (λem = 441 nm, PLQE = 45 %), and is trialled as an emitter in four OLED devices. A synthetic and photophysical investigation of several novel organic compounds and dinuclear zinc(II) complexes is presented in Chapter 5, however, the dinuclear complexes are not isolated. Four mononuclear zinc(II) complexes, five diimines, and one organic compound are presented. The organic compound has highly efficient, deep blue emission in solution (λem = 388 – 456 nm, PLQE = 83 %), and is further investigated as an emitter for OLEDs.

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