Blue-to-green electrophosphorescence from iridium(III) complexes with cyclometalated pyrimidine ligands

A series of 4, 6-disubstituted pyrimidine based iridium(III) complexes (1-5), has been synthesized with a simple method. Single X-ray structural analyses were conducted on 5 to reveal their coordination arrangement. These complexes exhibit almost single peak emission with the peak wavelength located in the range of 468-505 nm and quantum yields of over 75%. The relationship between photophysical properties and the substituent nature of the complexes was discussed by density functional theory. Organic light-emitting diodes (OLEDs) were also fabricated using these complexes as dopants in 15 wt%. The green device based on 1 shows a maximum external quantum efficiency, current efficiency, and power efficiency of 9.7%, 46.5 cd A(-1) and 29.0 1m W-1, respectively, while the blue device based on 5 exhibits an external quantum efficiency of up to 14.5%, peak luminance efficiency of 28.0 cd A(-1) and power efficiency of 19.5 1m W-1. Moreover, the Commission Internationale de L'Eclairage (CIE) coordinates of 5 are (0.15, 0.30) which is closer to blue emission than that of FIrpic.