Manipulating Charge‐Transfer Character with Electron‐Withdrawing Main‐Group Moieties for the Color Tuning of Iridium Electrophosphors

Abstract A new and synthetically versatile strategy has been developed for the phosphorescence color tuning of cyclometalated iridium phosphors by simple tailoring of the phenyl ring of ppy (Hppy = 2‐phenylpyridine) with various main‐group moieties in Ir(ppy‐X) 2 (acac) (X = B(Mes) 2 , SiPh 3 , GePh 3 , NPh 2 , POPh 2 , OPh, SPh, SO 2 Ph). This can be achieved by shifting the charge‐transfer character from the pyridyl groups in some traditional iridium ppy‐type complexes to the electron‐withdrawing main‐group moieties and these assignments were supported by theoretical calculations. This new color tuning strategy in Ir III ‐based triplet emitters using electron‐withdrawing main‐group moieties provides access to Ir III phosphors with improved electron injection/electron transporting features essential for highly efficient, color‐switchable organic light‐emitting diodes (OLEDs). The present work furnished OLED colors spanning from bluish‐green to red (505–609 nm) with high electroluminescence efficiencies which have great potential for application in multicolor displays. The maximum external quantum efficiency of 9.4%, luminance efficiency of 10.3 cd A −1 and power efficiency of 5.0 lm W −1 for the red OLED (X = B(Mes) 2 ), 11.1%, 35.0 cd A −1 , and 26.8 lm W −1 for the bluish‐green device (X = OPh), 10.3%, 36.9 cd A −1 , and 28.6 lm W −1 for the bright green device (X = NPh 2 ) as well as 10.7%, 35.1 cd A −1 , and 23.1 lm W −1 for the yellow‐emitting device (X = SO 2 Ph) can be obtained.