Efficient 1-(thiophen-2-yl)isoquinoline-based ionic iridophosphors with bulky counterions for solution-processed deep-red electroluminescence

A pair of high-efficiency deep-red emissive ionic iridophosphors ( Ira and Irb ) showing high photoluminescence quantum yields (PLQYs) are rationally designed by using 1-(thiophen-2-yl)isoquinoline as the cyclometalating ligand. Two bulky tetraarylborate anions (tetraphenylborate and tetrakis(3,5-bis(trifluoromethyl)phenyl)borate) are selected to improve their PLQYs in both solution and aggregated states, which enables efficient electroluminescence via a solution-processed approach. The variation of the tetraarylborate anions also aims to tune the photophysical properties of these deep-red emissive iridophosphors. Both ionic iridophosphors emit intense deep-red room-temperature phosphorescence in both solution and aggregated states. The phosphorescence spectra of both complexes are similar (630 nm with a shoulder emission of 686 nm) in CH 2 Cl 2 , originating from the same cationic species of the complexes. Both complexes show high PLQYs in CH 2 Cl 2 (0.41 for Ira , 0.43 for Irb ) and neat films (0.27 for Ira , 0.34 for Irb ). Moreover, they serve as triplet emitters to evaluate their performance in solution-processed deep-red electroluminescent devices. The maximum external quantum efficiencies for the deep-red electroluminescence are 7.3% with an emission maximum of 649 nm for Ira , and 10.2% with an emission maximum of 635 nm for Irb , respectively, implying that they are good candidates for high-performance electroluminescence. A pair of new deep-red emissive ionic iridium( iii ) complexes showing high photoluminescence quantum yields are designed by incorporating bulky tetraarylborate anions for efficient solution-processed electroluminescence.