Role of wide bandgap host in the degradation of blue phosphorescent organic light-emitting diodes

Yang, Rong; Li, X. M.; Cao, X. A.

doi:10.1063/1.4998166

Cited by 17 publications

(11 citation statements)

References 26 publications

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“…However, it is noted that the lifetime of both the TPBi and Bphen devices is not very long and comparable with some results of fluorescent OLEDs reported by other groups [31,32,33]. Our results suggest that current stressing may induce joule heating, causing accelerated device degradation [19,29,30]. Besides, concentration quenching, often referred to as singlet exciton-charge annihilation, may also exist in our devices with high concentration (20 wt.%) BCzVBi doped in the host [34].…”

Section: Resultssupporting

confidence: 89%

“…The lifetime of our devices is higher than those of some phosphorescent OLEDs with the mCP host because of the better stability of fluorescent materials [18,29,30], which meets our initial expectation. However, it is noted that the lifetime of both the TPBi and Bphen devices is not very long and comparable with some results of fluorescent OLEDs reported by other groups [31,32,33].…”

Section: Resultssupporting

confidence: 73%

“…[27] The different charge mobilitis of the host may mainly affect the location and width of the recombination zone, governing the behaviors of charge injection and transport in the EML. [28,29]…”

Section: Resultsmentioning

confidence: 99%

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Effects of Charge Transport Materials on Blue Fluorescent Organic Light-Emitting Diodes with a Host-Dopant System

et al. 2019

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High efficiency blue fluorescent organic light-emitting diodes (OLEDs), based on 1,3-bis(carbazol-9-yl)benzene (mCP) doped with 4,4’-bis(9-ethyl-3-carbazovinylene)-1,1’-biphenyl (BCzVBi), were fabricated using four different hole transport layers (HTLs) and two different electron transport layers (ETLs). Fixing the electron transport material TPBi, four hole transport materials, including 1,1-Bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC), N,N’-Di(1-naphthyl)-N,N’-diphenyl-(1,1’-biphenyl)-4’-diamine(NPB), 4,4’-Bis(N-carbazolyl)-1,1,-biphenyl (CBP) and molybdenum trioxide (MoO3), were selected to be HTLs, and the blue OLED with TAPC HTL exhibited a maximum luminance of 2955 cd/m2 and current efficiency (CE) of 5.75 cd/A at 50 mA/cm2, which are 68% and 62% higher, respectively, than those of the minimum values found in the device with MoO3 HTL. Fixing the hole transport material TAPC, the replacement of TPBi ETL with Bphen ETL can further improve the performance of the device, in which the maximum luminance can reach 3640 cd/m2 at 50 mA/cm2, which is 23% higher than that of the TPBi device. Furthermore, the lifetime of the device is also optimized by the change of ETL. These results indicate that the carrier mobility of transport materials and energy level alignment of different functional layers play important roles in the performance of the blue OLEDs. The findings suggest that selecting well-matched electron and hole transport materials is essential and beneficial for the device engineering of high-efficiency blue OLEDs.

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Section: Resultssupporting

confidence: 89%

Section: Resultssupporting

confidence: 73%

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Effects of Charge Transport Materials on Blue Fluorescent Organic Light-Emitting Diodes with a Host-Dopant System

et al. 2019

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“…It should be noted that mCP was chosen as the host material due to its high-lying singlet excited state (3.6 eV) that matches well with the wide band gap blue light OLED emitters for efficient FRET. 51,52 The luminance of device A was 10 cd/m 2 when a bias voltage of 7.4 V was applied to the organic heterostructure (Figure 4b). Although the onset voltage is considerable, but it is possible to reduce it by introducing additional electron-and hole-blocking layers.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

(Tetrafluorovinylphenyl)carbazole as a Multifunctional Material for OLED Applications

Ivaniuk

Stakhira

Yaremchuk

et al. 2023

ACS Appl. Electron. Mater.

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The multifunctional materials for application in organic light-emitting devices (OLEDs) based on a single structural motif are very desired but quite rare species. Such structures allow simplifying the chemical variety within OLED heterostructures and thus reducing their cost, manufacturing time, and logistic efforts. In this paper, we report the 9-(2,3,5,6-tetrafluoro-4-vinylphenyl)carbazole molecule (Cz4FS) utilized as a fluorescent emitter, host material for quantum dot based OLEDs (QLEDs), acceptor part of the exciplex active layer, and monomer that can be used for the preparation of emissive polymers and copolymers. The external quantum efficiency (EQE) of the corresponding fluorescent OLED based on a Cz4FS single emitter doped into a 1,3-bis(carbazol-9-yl)benzene matrix is 4.2%, which is close to the theoretical limit and maximum brightness at the level of 3600 cd/m2. An OLED based on exciplex emission obtained utilizing Cz4FS as an acceptor demonstrates higher efficiency (5.3%) and much higher brightness near 25 000 cd/m2. A QLED based on Cz4FS as a host for CdSeS/ZnS core–shell quantum dots demonstrates excellent energy transfer from the Cz4FS matrix that results in a clear spectrum of quantum dots with an EQE of 2.3%, maximum of 19 000 cd/m2, and narrow spectral distribution. An OLED based on a Cz4FS-based polymer and copolymer demonstrates not extraordinary efficiency but low-efficiency roll-off in a wide range of current densities.

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“…[1][2][3] However, compared with fluorescent OLEDs, the device lifetime of phosphorescent OLEDs (PhOLEDs) is relatively short since the triplet-involved degradation is accelerated due to the To suppress the triplet-involved degradation processes, both the reaction rate of the bimolecular process and the population density of the triplet excitons must be regarded as important factors in realizing operationally stable PhOLEDs. Previous papers have reported the host effect on the degradation of OLEDs in terms of exciton stability, [21] charge balance, [22][23][24] aggregation, [25,26] electrochemical stability, [27] and BDE; [16] however, the host-dependent degradation phenomena related to the exciton management characteristics of the host have, as yet, not been fully understood.…”

Section: Introductionmentioning

confidence: 99%

Quantitative Correlation of Triplet Exciton Management in Host with the Device Lifetime of Blue Phosphorescent Organic Light‐Emitting Diodes

Kim

Lee

2021

Advanced Optical Materials

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The improvement of the device stability of blue phosphorescent organic light‐emitting diodes (PhOLEDs) has proven to be a challenging issue in terms of enhancing the efficiency of blue organic light‐emitting diodes in practical applications. This work comprehensively investigates the exciton dynamics of electroplex hosts and quantitatively correlates the steady‐state triplet excitons in the host with the device lifetime of state‐of‐the‐art blue PhOLEDs. The kinetic processes of electrically generated singlet excitons, triplet excitons, and polarons explored via transient electroluminescence and numerical modeling reveal that the triplet exciton density in the host is governed by reverse intersystem crossing and the triplet–triplet annihilation rates. A degradation modeling that takes into account the simultaneous material degradation due to the triplet excitons in the host and the dopant is newly established. The results indicate that the suppressed host degradation due to the reduction (1.5×) in host triplet excitons leads to enhanced operational stability. The characterization method and the numerical modeling in this work facilitate the determination of the exciton and polaron behavior of the host and allow for predicting the host‐dependent device lifetime of PhOLEDs for specific host materials.

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Role of wide bandgap host in the degradation of blue phosphorescent organic light-emitting diodes

Cited by 17 publications

References 26 publications

Effects of Charge Transport Materials on Blue Fluorescent Organic Light-Emitting Diodes with a Host-Dopant System

Effects of Charge Transport Materials on Blue Fluorescent Organic Light-Emitting Diodes with a Host-Dopant System

(Tetrafluorovinylphenyl)carbazole as a Multifunctional Material for OLED Applications

Quantitative Correlation of Triplet Exciton Management in Host with the Device Lifetime of Blue Phosphorescent Organic Light‐Emitting Diodes

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