Synthesis and Electroluminescence Characterization of Mixed-C^N Ligand Tris-cyclometalated Ir(Ⅲ) Complexes†

doi:10.7503/cjcu20180334

Abstract

Abstract:

Two novel mixed 4-methyl-2,5-diphenylpyridine(MDP)/5-methyl-2-phenylpyridine(PMP) tris-cyclometalated iridium complexes Ir(MDP)₂(PMP)(complex 1) and Ir(MDP)(PMP)₂(complex 2) have been synthesized and characterized systematically in terms of their photophysical and electrochemical properties, and the effect of the molecular and the stacking structure on the photoelectric performance was investigated through the single crystal structure and theoretical calculation. The phosphorescent organic light-emitting diodes(PhOLEDs) based on both new phosphors showed the rather high maximum external quantum efficiency(EQE) of 22.4% and 20.7%, and maximum power efficiency(PE) values of 86.0 and 77.5 lm/W respectively, with the low efficiency roll-off.

Key words: Electrophosphorescence, Iridium complex, Mixed-C^N ligand(Ed.: F,K,M)

CLC Number:

O614.82
O626

TrendMD:

MA Xiaoyu,LIANG Jie,YE Ling,FAN Yong,XU Jianing,YE Kaiqi. Synthesis and Electroluminescence Characterization of Mixed-C^N Ligand Tris-cyclometalated Ir(Ⅲ) Complexes^†[J]. Chem. J. Chinese Universities, 2018, 39(10): 2129.

Figures/Tables 9

Scheme 1 Synthetic procedure of complexes 1 and 2 as well as chemical structures of the corresponding homoleptic complexes 1R and 2R

Fig.1 X-ray molecular structures of complexes 1(A) and 2(B), and packing structures of complexes 1(C) and 2(D)

Fig.2 UV-Vis absorption and PL spectra of complexes 1 and 2 in degassed solution(CH2Cl2, 300 K) as well as PL spectra of complexes 1 and 2 in glass toluene(77 K)Inset: PL spectra of complexes 1R(a) and 2R(b) in degassed solution(CH2Cl2, 300 K).

Fig.3 Transient PL decay profile of complexes 1(a) and 2(b) in neat film

Table 1 Lifetime test data of complexes 1 and 2

Complex	A₁	t₁/ns	A₂	t₂/ns
1	9360.22	60.22	1952.96	107.89
2	14108.03	75.07	153.33	534.31

Fig.4 TGA(A) and DSC(B) curves of complexes 1(a) and 2(b)

Fig.5 Cyclic voltammetry(CV) curves of complexes 1(a) and 2(b)

Fig.6 Energy diagram of the materials used in the PhOLEDs(A), EL spectra of D1 and D2 at the practical luminance of 1000 cd/m2(B), current density-voltage-luminance(J-V-L) curves of D1 and D2(C) and power efficiency(PE)-luminance-external quantum efficiency(EQE) curves of D1 and D2(D)

Table 2 EL data of devices D1 and D2

Device	$V turn ? on a$ /V	L_max /(cd·m^-2)(V at L_max)	PE ^b/(lm·W^-1)	EQE ^b(%)	EL, $λ max c$ / nm
D1	2.7	59730(9.1 V)	86.0, 60.2, 41.5	22.4, 21.3, 19.2	524
D2	2.7	55460(9.2 V)	77.5, 56.9, 40.1	20.7, 19.8, 18.1	520

Table 2 EL data of devices D1 and D2

Device	$V turn ? on a$ /V	L_max /(cd·m^-2)(V at L_max)	PE ^b/(lm·W^-1)	EQE ^b(%)	EL, $λ max c$ / nm
D1	2.7	59730(9.1 V)	86.0, 60.2, 41.5	22.4, 21.3, 19.2	524
D2	2.7	55460(9.2 V)	77.5, 56.9, 40.1	20.7, 19.8, 18.1	520

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