Diphenylamine/triazine hybrids as bipolar hosts for phosphorescent organic light-emitting diodes

Blue organic light‐emitting diodes (OLEDs) have been a bottleneck for OLEDs lighting and flexible displays. Improving the operational lifetimes and simultaneously decreasing efficiency roll‐off while maintaining high quantum efficiency is currently a challenge in the scientific community and industry. Optimizing the fabrication process of devices and developing stable and efficient luminescence and transporting materials and developing host materials with high triplet energy is an effective way to overcome this obstacle. On the one hand, the host material can disperse the blue emitters to reduce the possibility of exciton annihilation. On the other hand, it can adjust the carrier transport, exciton formation, and energy transfer in the device. In recent years, many efforts have been undertaken for the design, synthesis, and applications of the novel host. A systematic summary and comments on the recent advances of high triplet energy hosts for blue OLEDs are provided here, which specifically include bipolar transport hosts, single thermally activated delayed fluorescence (TADF) hosts, TADF assistant hosts, exciplex hosts, exciplex free type mixed hosts, and electroplex hosts. Moreover, future prospects for host for high performance blue OLEDs are also proposed.

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“…Blue, green, red, and white PhOLED based on TDPA‐TRZ as hosts demonstrated EQE max of over 20% with small efficiency roll‐off. [ 88 ]…”

Section: The Categories Application and Performance Of High Tripletmentioning

confidence: 99%

High Triplet Energy Hosts for Blue Organic Light‐Emitting Diodes

Wang

Yun

Wang

et al. 2020

Adv Funct Materials

145

112

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“…Herein, we designed and synthesized two groups of isomers (BP-DPA and BP-DMAc) based on biphenyl (BP) through changing the positions of diphenylamine (DPA) and 9,9-dimethyl-9,10-dihydroacridine (DMAc), which were named as N 2 ,N 2 ,N 2' ,N 2' -tetraphenyl-[1,1'-biphenyl]-2,2'-diamine (o-DDPA), N 3 ,N 3 ,N 3' ,N 3' -tetraphenyl-[1,1'-biphenyl]-3,3'-diamine (m-DDPA), N 4 ,N 4 ,N 4' ,N 4' -tetraphenyl-[1,1'-biphenyl]-4,4'-diamine (p-DDPA), 2,2'-bis(9,9-dimethylacridin-10(9H)-yl)-1,1'-biphenyl (o-DDMAc), 3,3'-bis(9,9-dimethylacridin-10(9H)-yl)-1,1'-biphenyl (m-DDMAc), and 4,4'-bis(9,9-dimethylacridin-10(9H)-yl)-1,1'-biphenyl (p-DDMAc), respectively. DPA and DMAc were donors widely used in luminescent materials [17,19,25,26] and biphenyl was utilized due to its simple structure. Expectably, the steady state conformations and luminescent efficiencies of the isomers were distinctly different.…”

Section: Introductionmentioning

confidence: 99%

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

Cui

Li³

et al. 2022

ChemistrySelect

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Herein, two series of isomers are developed based on biphenyl (BP) and two typical donor groups diphenylamine (DPA) and 9,9-dimethyl-9,10-dihydroacridine (DMAc) to figure out the isomerization effect on structures and photophysical properties. The computational simulations and photophysical analyses indicate that the substitution positions influence not only the molecular conformations but also the frontier molecular orbital distributions, which further influence the photoluminescence properties. We find that twisted structure is beneficial for the separation of the frontier molecular orbitals, while more planar structure contributes to higher luminescent intensity for both fluorescence and phosphorescence. Meanwhile, room temperature phosphorescence (RTP) is caught when these isomers are doped in 4,4'-dibromo-1,1'-biphenyl (DBBP). The p-DDPA/DBBP complex shows the highest intensity of phosphorescence and the longest lifetime (81.71 ms). The photoluminescence quantum yield of the p-DDPA/DBBP complex is as high as 54 % with RTP quantum efficiency approximately 12 %, which is 28 % for pure p-DDPA without afterglow.

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“…[ 12 ] With the aim to obtain bipolar host, a wide variety of donor–acceptor compounds were developed recently. [ 13 ] The widely used design strategy for bipolar hosts is linking of electron‐donating and electron‐withdrawing moieties via core linker. [ 14 ] The different structural linkage modes ( ortho, meta , and para ) affect the π‐conjugation.…”

Section: Introductionmentioning

confidence: 99%

Does Through‐Space Charge Transfer in Bipolar Hosts Affect the Efficiency of Blue OLEDs?

Macionis

Gudeika

Volyniuk

et al. 2021

Advanced Optical Materials

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Additional energy loss pathways which occur in blue electrophosphorescent devices via through‐space charge transfer (TSCT) states of bipolar hosts are identified for the first time in this study. Blue phosphorescent organic light‐emitting diodes (PhOLEDs) with maximum external quantum efficiency from 22.7 to 30.5% are fabricated using new bipolar derivatives of benzimidazole, linked through phenyl spacer with different number of tert‐butyl substituted carbazoles, as hosts. Applicability of the newly synthesized compounds as hosts for blue PhOLEDs is justified by their high triplet levels (2.94–2.98 eV), bipolar charge‐transporting properties with charge mobilities up to 2.34 × 10−3 cm2 V−1 s−1 at electric field of 2.7 × 105 V cm−1, and high ionization potentials (5.63–5.81 eV). Weak microsecond‐lived emission, which is attributed to TSCT, is detected for the developed bipolar hosts. The different efficiencies of the fabricated PhOLEDs are partly related to energy losses via TSCT states, the presence of which is detected for the developed donor–acceptor hosts in both solution and solid‐state. To prevent energy losses through TSCT in PhOLEDs, the excited state energy of emitter has to be lower than triplet levels of bipolar host. It also has to be lower than the TSCT energy level of bipolar host for the fabrication highly efficient PhOLEDs.

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Diphenylamine/triazine hybrids as bipolar hosts for phosphorescent organic light-emitting diodes

Abstract: Bipolar host materials employing diphenylamine as a donor unit and triazine as an acceptor unit have been developed for high performance phosphorescent organic light-emitting diodes.

Cited by 17 publications

References 37 publications

High Triplet Energy Hosts for Blue Organic Light‐Emitting Diodes

High Triplet Energy Hosts for Blue Organic Light‐Emitting Diodes

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

Does Through‐Space Charge Transfer in Bipolar Hosts Affect the Efficiency of Blue OLEDs?

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