Photophysical and Electro-Optical Properties of Copolymers Bearing Blue and Red Chromophores for Single-Layer White OLEDs

In this study, novel copolymers consisting of blue and red chromophores are presented to induce emission tuning, enabling the definition of white light emission in a single polymeric layer. These aromatic polyether sulfones exhibit high molecular weights, excellent solubility and processability via solution deposition techniques. In addition, by carefully controlling the molar ratios of chromophores composition, the energy transfer mechanism, from blue to red chromophores, takes place enabling us to define properly the emission covering the entire range of the visible spectrum. The optical and photophysical properties of the monomers and copolymers were thoroughly investigated via NIR-Vis-far UV Spectroscopic Ellipsometry (SE), Absorbance and Photoluminescence (PL). These copolymers are used as an emissive layer and applied in solution-processed WOLED devices. The fabricated WOLED devices have been subsequently studied and characterized in terms of their electroluminescence properties. Finally, the WOLED devices possess high color stability and demonstrate CIE Coordinates (0.33, 0.38), which approach closely the pure white light CIE coordinates.

Anthracene Green Fluorescent Derivatives Based on Optimized Side Groups for Highly Efficient Organic Light-Emitting Diode Emitters

Two green fluorescent materials, N,N,N′,N′-Tetra-o-tolyl-anthracene-9,10-diamine (o-Me-TAD) and N,N′-bis(2,5-dimethylphenyl)-N,N′-di-o-tolylanthracene-9,10-diamine (DMe-o-Me-TAD) including anthracene and diphenylamine moiety, were synthesized by Buchwald-Hartwig amination. In solution state, PL maximum wavelength of o-Me-TAD and DMe-o-Me-TAD is 518 nm and 520 nm. The doped device using o-Me-TAD as green fluorescent dopant exhibited CE of 19.78 cd/A and EQE of 5.97%. The doped device using DMe-o-Me-TAD as dopant exhibited CE of 22.37 cd/A and EQE of 7.02% without roll-off. Doped devices fabricated using o-Me-TAD and DMe-o-Me-TAD show the EL peaks at 522 and 523 nm corresponding to the Commission Internationale de L’Eclairage (CIE) coordinates of (0.29, 0.63) and (0.27, 0.61).

Benzimidazole-Based N,O Boron Complexes as Deep Blue Solid-State Fluorophores

Benzimidazole-based boranils were designed and synthesized in order to assess the influence of halogen substituents on their optoelectronic properties. All compounds are photoluminescent in solution and solid state. Compared to the free ligands, the new boranils emit at a lower wavelength, by elimination of the excited-state intramolecular proton transfer observed with the ligands. In the solid state, some of the boranils exhibit a deep blue emission, presenting Commission Internationale de l’Éclairage (CIE) coordinates with an x-component of less than 0.16 and a y-component smaller than 0.04, highly desired values for the development of blue emitting materials.

9-(10-phenylanthracen-9-yl)-Benzo[b]Fluoreno[3,4-d] Thiophene Derivatives for Blue Organic Light-Emitting Diodes

In this study, two blue fluorescence materials using phenylanthracene-substituted fluorene derivatives were synthesized and characterized for organic light-emitting diodes (OLEDs). To study their electroluminescent properties, OLED devices were fabricated using these two materials as emissive layer (EML). A device using 7,7-diphenyl-9-(10-phenylanthracen-9-yl)-7H-benzo[b]fluoreno[3,4-d]thiophene in emitting layer showed the highest value of EQE value which is 3.51%. It also showed the luminance efficiency of 3.22 cd/A and power efficiency of 2.89 lm/W with the CIE coordinates (0.15, 0.09).

Efficient blue thermally activated delayed fluorescent emitters based on a boranaphtho[3,2,1-de]anthracene acceptor

Efficient blue thermally activated delayed fluorescent emitters based on organic boron-acceptor are developed with high external quantum efficiencies and finely tuned CIE coordinates.

Indenofluorene- and carbazole-based copolymers for blue PLEDs with simultaneous high efficiency and good color purity

Indenofluorene- and carbazole-based copolymers have been developed for use in high-performance blue PLEDs with a promising EQE of 4.12% and CIE coordinates of (0.150, 0.081).

Sky-blue iridium complexes with pyrimidine ligands for highly efficient phosphorescent organic light-emitting diodes

Three sky blue heteroleptic Ir(III) complexes with emission peaks at 457–459 nm, have been developed. A maximum quantum efficiency of 21.23% with CIE coordinates of (0.15, 0.26) is realized in their PhOLEDs, representing a higher efficiencies and improved color purities than FIrpic.

Two novel aromatic hydrocarbons: facile synthesis, photophysical properties and applications in deep-blue electroluminescence

Novel solution processable aromatic hydrocarbons have been designed and synthesized for deep-blue OLEDs with a maximum emission peak of 410 nm and CIE coordinates of (0.16, 0.08).

Fluorine-Substituted Phenanthro[9,10-d]imidazole Derivatives with Optimized Charge-Transfer Characteristics for Efficient Deep-Blue Emitters

The development of high-efficiency deep-blue emitters is of great importance for full-color organic light-emitting diodes (OLEDs). In this contribution, three difluorine-substituted phenanthro[9,10-d]imidazole derivatives with optimized charge-transfer character and deep-blue emission have been developed. It is demonstrated that the fluorine substitution can facilitate the “state mixing” of singlet and triplet excitons, which increases the utilization of triplet excitons. The fluorine substitution also brings more intermolecular interactions which have influence on the molecular packing pattern of the solid states, ultimately impacting their carrier mobilities. Through fine-tuning of molecular structures, 4'-(1-(3,5-difluorophenyl)-1H-phenanthro[9,10-d]imidazol-2-yl)-N,N-diphenyl-[1,1'-biphenyl]-4-amine (2FPPIDPA) realized a high exciton utilization ratio with Commission Internationale de L'Eclairage (CIE) coordinates of (0.156, 0.046), and 4'-(1-(3,5-difluorophenyl)-1H-phenanthro[9,10-d]imidazol-2-yl)-N,N-diphenyl-[1,1'-biphenyl]-4-amine (2FPPIDPA) achieved an external quantum efficiency of 8.47% with CIE coordinates of (0.152, 0.083) in multilayer OLEDs. Due to their good hole-transport abilities, double-layer OLEDs without the hole-transport layer showed performances comparable or even superior to the multilayer ones.