Design, synthesis and characterization of a new blue phosphorescent Ir complex

Abstract

As being incompatible with host materials in a physically blended emitting layer, phosphorescent dye is prone to form aggregation induced by Joule heat in devices under work. In this work, a new and efficient blue phosphorescent dye Cz-C8-FIrpic was designed and synthesised by incorporating 9-phenyl-9H-carbazole into a commonly used blue emissive iridium complex bis(4,6-(difluorophenyl)pyridine-N,C 2 ′)picolinate (FIrpic) via an alkyl chain linkage. This phosphorescent dye exhibits similar photophysical properties to the units of FIrpic and 9-phenyl-9H-carbazole in solutions. In solid films of Cz-C8-FIrpic, the energy transfer from 9-phenyl-9Hcarbazole to FIrpic units is effective. The Cz-C8-FIrpic doped emissive layer was investigated by AFM, STEM−EDS, transient photoluminescence decay curve and molecular dynamics simulations. The results show that in the Cz-C8-FIrpic doped film the phase aggregation of FIrpic units is less severe than that in the typically used FIrpic film. In addition, the optimized Cz-C8-FIrpic based device achieved a maximum luminance of 25142 cd m -2 , a maximum EQE of 8.5% and a maximum current efficiency of 22.5 cd A -1 which is about 15 % higher than that of the control device based on FIrpic. We conclude that grafting a typically used dye to functional groups with alkyl chains is useful to restrict phase separation in physically blended emitting layers, and thus can achieve high electroluminescence performances.

Not All Bis[2-(4,6-difluorophenyl)pyridyl-N,C2′]iridium(III) Picolinate (FIrpic) Isomers Are Unsuitable for Developing Long-Lifetime Blue Phosphorescent Organic Light-Emitting Diodes

“…These isomers also exhibit similar maximum absorption peak and vertical excited energies of lowest singlet (S 1 ) and triplet (T 1 ) excited states. The calculated results also agree with the experimental data, 15 which demonstrated that the four isomers have similar optoelectronic properties.…”

Molecular Dynamics Simulation in Compatibility and Mechanical Properties of Chloroprene Rubber/Polyurethane Blends

“…The radial distribution function (RDF) is a physical quantity that responds to the microstructure of a material and represents the ratio of the probability density of the occurrence of another atom or molecule at a distance around an atom or molecule to the probability density of a random distribution, solved by the equation: [ 39 ] $$$$\begin{equation}{g_{AB}}\left( r \right) = \frac{1}{{4\pi {r^2}}}\;\frac{{\mathop \sum \nolimits_{t=1}^K \mathop \sum \nolimits_{j=1}^{{N_{AB}}} \Delta {N_{AB}}\left( {r \to r + \delta r} \right)}}{{{N_{AB}}K}}\end{equation}$$$$where 𝜌 𝐴𝐵 is the density of the system, 𝛿𝑟 is the distance difference, N AB is the number of atoms in the system A and B, Δ N AB is the number of atoms in the range r to r + 𝛿𝑟 where another atom appears, and K is the number of time steps.…”

Larger VH (Hole Distribution Volume)/VM (Molecular Volume) Induced Higher Charge Mobility of Group IVA Element-Based Host Materials for Potentially Highly Efficient Blue OLEDs

“…As the ratio of the singlet and triplet excitons formed in OLED devices is 1:3, harvesting triplet excitons plays a very important role in improving device efficiency, such as for phosphorescent and TADF OLEDs. Therefore, ideal blue host materials should have not only a high Δ E g but also a high triplet energy ( E T ) to prevent the reversing of triplet excitons.…”