Blue-emitting Ir(iii) phosphors with 2-pyridyl triazolatechromophores and fabrication of sky blue- and white-emitting OLEDs

Abstract

Heteroleptic Ir(III) complexes with 3-tert-butyl-5-(2-pyridyl)-1,2,4-triazolate chromophore (bptz) and cyclometalating benzyldiphenylphosphine (bdp) or phenyl diphenylphosphinite (pdpit) ancillary (i.e. [Ir(bptz)₂(bdp)] (1) and [Ir(bptz)₂(pdpit)] (2)) are synthesized upon treatment of [IrCl₃(tht)₃] (tht = tetrahydrothiophene) with the relevant phosphine, followed by the addition of 2 equiv. of bptz chelate at elevated temperature. Their photophysical properties in solution were measured, along with the characteristics detected as dopants in thin solid films. For application, organic light emitting diodes (OLEDs) were also fabricated using 1 and 2 as dopants, achieving respective maximum efficiencies of 17.8% (44.8 cd A⁻¹ and 46.3 lm W⁻¹) and 9.1% (22.8 cd A⁻¹ and 23.6 lm W⁻¹). In addition, sky blue iridium complex 1 was used with red osmium complex [Os(bpftz)₂(PPhMe₂)₂] (3) to fabricate phosphorescent OLEDs with a sophisticated red/blue/red emitting layer architecture, attaining a stable warm white color with CIE coordinates of (0.397, 0.411). This white OLED attained an electroluminescence efficiency of up to 18.1%, 39.6 cd A⁻¹, and 35.7 lm W⁻¹ for the forward direction.