Semitransparent Circularly Polarized Phosphorescent Organic Light‐Emitting Diodes with External Quantum Efficiency over 30% and Dissymmetry Factor Close to 10⁻²

Abstract

To concurrently realize large electroluminescence dissymmetry factor and high device efficiency remains a formidable challenge in the development of circularly polarized organic light‐emitting diode (CP‐OLED). In this work, by introducing a famous chiral resource of R‐camphor, two green chiral iridium(III) isomers of Λ/Δ‐Ir‐(R‐camphor) containing dual stereogenic centers at iridium and ancillary ligand, are efficiently synthesized. Benefiting from their high phosphorescence quantum yields (≈93%) and obvious circularly polarized photoluminescence property with dissymmetry factors (|gPL|) in the 10−3 order of magnitude, the circularly polarized phosphorescent organic light‐emitting diodes using these chiral emitters show excellent performances with the maximum external quantum efficiency (EQEmax) of 30.6%, low efficiency roll‐off, and intense circularly polarized electroluminescence signal with dissymmetry factor (gEL) in the 10−4 order of magnitude. By the novel device engineering with semitransparent cathode, the resulting gEL values are significantly boosted by one order of magnitude, up to 7.70 × 10−3, which is the highest among the CP‐OLEDs with chiral iridium complexes. Noteworthy, the semitransparent devices deliver a record‐high EQEmax of 18.8% among the semitransparent OLEDs. The combination of novel chiral Ir(III) complexes and the semitransparent devices sheds light on the development of high performance CP‐OLEDs with simultaneously high efficiency and large dissymmetry factor.

External Magnetic Field Driven, Ambidextrous Circularly Polarized Electroluminescence from Organic Light Emitting Diodes Containing Racemic Cyclometalated Iridium(III) Complexes

“…In recent years, chiral emitters exhibiting circularly polarized luminescence (CPL), with high quantum yield (Φ PL ) and high anisotropy factor (g CPL ), upon excitation with unpolarized light have been used in numerous applications such as circularly polarized electroluminescence (CPEL) devices and security inks. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] Several chiral p-block organic [16][17][18][19][20][21][22] and d-block/f-block organometallic compounds [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36] are efficient fluorescent and phosphorescent emitters, respectively, with narrow CPL bandwidths and high g CPL values in the visible region, making themselves suitable for producing high-performance CPELs. However, it is difficult to obtain a high yield of enantiomerically pure isomers in less time, at a reasonable cost, using green methods.…”

“…Considerable numbers of homoleptic tris-cyclometalated Ir(III) [23,[26][27][28]31,35,36] (as Δ-/Λ-forms in each fac/mer-isomer) and heteroleptic bis-cyclometalated Ir(III) [24,25,[28][29][30][33][34][35][36] (as Δ-/Λ-forms) complexes with achiral organic ligands have been investigated. They exhibit phosphorescence-based EL with high Φ PL and short photoluminescence (PL) lifetimes, owing to strong spin-orbit coupling in Ir(III).…”

“…Their PL wavelengths can be tailored by modifying their ligands. [23][24][25][26][27][28][29][30][31][32][33][34][35][36] The magnetic circularly polarized luminescence (MCPL) theory by Riehl and Richardson [37] prompted several experiments using symmetric, achiral, and racemic mixtures of lanthanide complexes with achiral ligands, under one of two possible Faraday geometries. [38][39][40][41] An external static magnetic (EMF) field is now established as a versatile physical bias that induces chiroptical spectral signals in the ground and photoexcited states of several achiral and racemic organic, and organometallic emitters.…”

“…They exhibit phosphorescence‐based EL with high Φ PL and short photoluminescence (PL) lifetimes, owing to strong spin‐orbit coupling in Ir(III). Their PL wavelengths can be tailored by modifying their ligands [23–36] …”

Structures and Photoluminescence Properties of Bis(aromatic amino)‐Based Isomers with Biphenyl as Bridge

“…[14][15][16][17][18][19][20][21] Recently, researches concentrating on the relationship of structures and properties of pure organic luminescent materials have drawn scientists' attention. [22][23][24] However, few researches are focused on the relationship of luminescent properties and pure organic luminescent isomers based on simple aryl core which is easily synthesized and contrasted.…”