Effect of dendrimer generation and surface groups on the optoelectronic properties of green emitting bis-tridentate iridium(iii) complexes designed for OLEDs

Abstract

The role of surface groups (t-butyl versus 2-ethylhexyloxy) and dendron generation (first versus second) on the photoluminescent and electroluminescent properties of solution-processable bis-tridentate iridium(iii) complexes has been investigated.

Solution-processed dendrimer-based bis-tridentate iridium(iii) complexes with red, green, and blue phosphorescence for white OLEDs

“…Before discussing the performance of OLEDs composed of the dendrimers, we also measured the PL and PLQYs of films composed of 1 mol% of the dendrimers in 4,4′,4-tris(carbazol-9-yl)triphenylamine (TCTA), which was the concentration that gave the optimal device performance and matched the concentration previously used for the D-Green -based OLEDs. 18 It should be noted that the blend films were slightly hazy. For blend films in which the host has relatively poor solubility, it is the dendrimer that provides the film forming properties.…”

“…However, there have been two reports of green emissive bis-tridentate iridium( iii ) complex-cored dendrimers that have given rise to efficient solution-processed OLEDs. 17,18 Given that efficient green emissive bis-tridentate iridium( iii ) complex-cored dendrimers exist, it is perhaps surprising that the strategy has not yet been used to develop blue and red emissive materials, which can then be combined to form WOLEDs with a solution-processed emissive layer.…”

“…Blue emission ( D-Blue ) was achieved through the addition of two fluorine groups to the phenyl ring and the attachment of a trifluoromethyl moiety to the pyrazole ring of the dianionic 6-pyrazolyl-2-phenylpyridine ancillary ligand. The green emissive dendrimer ( D-Green ) used in the WOLED was the same as previously reported, 18 and D-Red (red emitter) used the published iso-quinoline-based ancillary ligand to achieve the red emission. 19 We describe the syntheses of D-Blue and D-Red , the electrochemical and photophysical properties of the dendrimers, and their performance in simple monochrome and WOLED structures.…”

“…The synthesis of D-Green has been previously reported 18 and the syntheses of D-Blue and D-Red followed a similar strategy (Scheme 1). The synthesis of L 1 H required for D-Blue was achieved in a three-step procedure.…”