Structure–Property Relationship in Amber Color Light-Emitting Electrochemical Cell with TFSI Counteranion: Enhancing Device Performance by Different Substituents on N∧N Ligand
Articles > Article · 2021
Authors: Nuriye Demir, Merve Karaman, Gul Yakali, TUĞBA ARİFİOĞLU, Serpil DENİZALTI, ŞERAFETTİN DEMİÇ, Bircan DİNDAR, MUSTAFA CAN
Inorganic Chemistry, Journal Indexed in SCI Expanded, International, WoS, 2021, vol 60, pp 4410-4423
DOI: 10.1021/acs.inorgchem.0c02939
Summary
Amber color emitting novel Ir(III) complexes were synthesized: [Ir(Meppy) 2 (Fpbpy)][PF 6 ] ( 1b PF 6 ), [Ir(Meppy) 2 (Fpbpy)][TFSI] ( 1b TFSI), [Ir(Meppy) 2 (MeObpy)][PF 6 ] ( 2b PF 6 ) and [Ir(Meppy) 2 (MeObpy)][TFSI] ( 2b TFSI), where Meppy = 2-( p -methylphenyl)-pyridine ( b ), Fpbpy = 4,4′-bis(4-fluorophenyl)-2,2′-bipyridine ( 1 ), and MeObpy = 4,4′-bis(4-methoxy)-2,2′-bipyridine ( 2 ). The photophysical and X-ray results showed that the complexes have aggregation-induced phosphorescent emission (AIPE) and a salt-induced polymorphism effect. The highest photoluminescence intensity was observed in complex 2b TFSI compared to other complexes in the solid state. Their theoretical absorption and phosphorescence emission transitions in acetonitrile were also investigated by using double- and triple-ζ basis sets with B3LYP and PBE0 hybrid functional. The best light-emitting electrochemical cell (LEC) performance was exhibited by complex 2b TFSI, and the data obtained were as follows: Luminance, current density, luminous efficiency, turn-on time, power efficiency, and external quantum efficiency were measured as 16 156 cd/m 2, 554 mA/cm 2, 8.49 cd/A, 17 s, 3.95 lm/W and 6.37%, respectively. The investigation of crystallographic characteristics have shown that the LEC performance of these complexes depends on cationic–anionic interaction which has a significant influence on molecular stacking of the molecules. Because, complex 2b TFSI, with weak cationic–anionic interactions, shows strong π···π stacking interactions between the adjacent molecules, it is the best lighting application candidate among the complexes.