Highly Efficient Light-Emitting Electrochemical Cells (LECs) from Host-Guest Cationic Iridium(III) Complexes

Abstract

Five charged iridium(III) complexes with a different number and position of methyl group; [Ir(phen)(ppy)2]PF6 (1), [Ir(4-phen)(ppy)2]PF6 (2), [Ir(2,9-phen)(ppy)2]PF6 (3), [Ir(4,7-phen)(ppy)2]PF6 (4) and [Ir(4,5,6,7-phen)(ppy)2]PF6 (5) were synthesized and characterized by NMR, IR, UV-Vis absorption, fluorescence spectroscopy and cyclic voltammetry. The host-guest light-emitting electrochemical cells (LECs) based on ITO/PEDOT:PSS/1-5:PVK (1:4)/Al were investigated, which resulted in a maximum current efficiency at 1.35 cdA −1 and a brightness at 717 cdm −2 from 5. The host-guest LECs can be improved by the insertion of the TPBi and LiF layers. We found that the highly efficient electroluminescence device gave the peak current efficiency to 4.49 cdA −1 , the maximum brightness at 1,200 cdm −2 with Commission Internationale de L'Eclairage (CIE) coordinates of (0.30, 0.54) from 3.

Highly Efficient Blue LECs Using Charged Iridium Complexes

“…The calculated energy gap of UM02 shows a value at 3.37 eV which is in agreement with the result from photophysical experiments (3.10 eV). In order to evaluate the electroluminescent properties, complexes were rst employed as emitting layer in both host-guest LECs [15] and OLEDs [16,17] where PVK and PBD were mixed as the co-host. PEDOT:PSS acts as hole-injecting layer to facilitate electron transport.…”

“…Heteroleptic charged iridium (III) species comprising two cyclometallating ligands and a neutral diimine ligand of generic formula (C ∧ N) 2 Ir(N ∧ N) + have been of great interest as multifunctional chromophores for advanced optoelectronic applications [16]. The key properties of these complexes are their high stabilities, high luminescence quantum yields, short excited state lifetime and tunable emission energies.…”

Charged Iridium(III) Complexes with Varied Side Chain Length in Organic Light Emitting Diodes

“…4 and summarized in Table 2. The OLED performances suggested that bis(4-alkoxyphenyl) substituted 4,5-diazafluorene derivatives gave a beneficial N^N ligand, compared with 3,4,6,7-tetramethyl-1,10-phenanthroline in previous work [15]. Moreover, the long alkyl chains (C6 and C8) showed the better OLEDs performances than C1.…”