Near‐IR Emitting Iridium(III) Complexes with Heteroaromatic β‐Diketonate Ancillary Ligands for Efficient Solution‐Processed OLEDs: Structure–Property Correlations

Abstract

Three NIR-emitting neutral Ir(III) complexes [Ir(iqbt)2 (dpm)] (1), [Ir(iqbt)2 (tta)] (2), and [Ir(iqbt)2 (dtdk)] (3) based on the 1-(benzo[b]thiophen-2-yl)-isoquinolinate (iqtb) were synthesized and characterized (dpm=2,2,6,6-tetramethyl-3,5-heptanedionate; tta=2-thienoyltrifluoroacetonate; dtdk=1,3-di(thiophen-2-yl)propane-1,3-dionate). The compounds emit between λ=680 and 850 nm with high luminescence quantum yields (up to 16 %). By combining electrochemistry, photophysical measurements, and computational modelling, the relationship between the structure, energy levels, and properties were investigated. NIR-emitting, solution-processed phosphorescent organic light-emitting devices (PHOLEDs) were fabricated using the complexes. The devices show remarkable external quantum efficiencies (above 3 % with 1) with negligible efficiency roll-off values, exceeding the highest reported values for solution-processible NIR emitters.

Iridium(III)‐Doped Core‐Shell Silica Nanoparticles: Near‐IR Electrogenerated Chemiluminescence in Water

“…The complexes, 1 and 2, were synthesized according to the reported procedure. [17] Dry acetonitrile (ACN) was refluxed over, and distilled from, CaH 2 and activated alumina super I neutral (ICN Biomedicals), and it was stored in a specially designed Schlenk flask over 3 activated molecular sieves, protected from light.…”

“…[11][12][13][14][15] In general, iridium complexes show typical reversible, monoelectronic, redox properties, high photoluminescence (PL) efficiencies with relatively short lifetimes (in microseconds regime) and photo-and chemical-stability. Most importantly, unlike ruthenium(II) complexes that typically show emission centered between 600 and 650 nm, iridium(III) complexes have the ability to span the emission range from the near-IR [16,17] to deep blue, [18] which is useful in the development of multichannel analytical techniques. [19] This can be obtained by careful selection of the cyclometalated ligand (N C) [20,21] or by introduction or modification of the ancillary ligands, (L X/O O).…”

“…The synthesis and preliminary photophysical and electrochemical investigation of such complexes were preliminary reported. [17] In this work, the ECL properties and efficiencies of such species have been investigated in acetonitrile or encapsulated in silica nanoparticles aqueous solutions. Both annihilation ECL (in organic solutions) and the co-reactant approach (in aqueous buffer) were used.…”

Unraveling the Degradation Mechanism of FIrpic-Based Blue OLEDs: I. A Theoretical Investigation

“…9 Density Functional Theory (DFT) and its time-dependent DFT (TDDFT) calculations provide a wealth of useful insights into the photodeactivation, inter-system crossing and non-radiative decay processes. [10][11][12][13][13][14][15][16][17][18][19][20][21] Calculations on Ir(ppy) 3 This open state is particularly favored in the triplet state. 22 The isomerization barriers of a small model Ir complex where calculated in Ref.…”

The Quantum Efficiency Roll-Off Effect in Near-Infrared Organic Electroluminescent Devices with Iridium Complexes Emitters

“…In these two papers the minor efficiency roll-off was also detected. More recently, photoluminescence quantum yields of up to 16% in the 680-850 nm range have been reported for iridium(III) complexes based on the 1-(benzo[b]thiophen-2-yl)-isoquinolinate (iqbt) cyclometalated emissive ligand, namely Ir(iqbt) 2 (dpm), Ir(iqbt) 2 (tta) and Ir(iqbt) 2 (dtdk), where dpm = 2,2,6,6-tetramethyl-3,5-heptanedionate, tta = 2-thienoyltrifluoroacetonate and dtdk = 1,3-di(thiophen-2-yl)propane-1,3-dionate [9,10]. Those compounds made it possible to obtain electroluminescence QE values of up to 3% from the solution-processed sandwich-type structures, characterized by a minor QE roll-off.…”