The influence of the mixed host emitting layer based on the TCTA and TPBi in blue phosphorescent OLED

Jiang, Zhong-Lin; Wu, Tian; Kou, Zhiqi; Cheng, Shuang; Li, Yihang

doi:10.1016/j.optcom.2016.04.002

Cited by 23 publications

(9 citation statements)

References 18 publications

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“…The development of such visible-light-active p-type OLPL systems that work in air will contribute to various future practical applications of OLPL systems. Cationic photoredox catalysts 2,4,6-triphenylpyrylium tetrafluoroborate (TPP + ) and 2,4,6-tris(methoxyphenyl)pyrylium tetrafluoroborate (MeOTPP + ) were used as electron acceptors 28,29,30 and semiconducting host molecules 3,3′-di(9H-carbazol-9-yl)biphenyl (mCBP) 31 and 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene (TPBi) 32 were used as electron donors (Fig. 1c).…”

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confidence: 99%

Organic long-persistent luminescence stimulated by visible light in p-type systems based on organic photoredox catalyst dopants

et al. 2021

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Organic long-persistent-luminescent (OLPL) materials demonstrating hour-long photoluminescence have practical advantages in applications owing to their flexible design and easy processability. However, the energy absorbed in these materials is typically stored in an intermediate charge-separated state that is unstable when exposed to oxygen, thus preventing persistent luminescence in air unless oxygen penetration is suppressed through crystallization. Moreover, OLPL materials usually require ultraviolet excitation. Here we overcome such limitations and demonstrate amorphous OLPL systems that can be excited by radiation up to 600 nm and exhibit persistent luminescence in air. By adding cationic photoredox catalysts as electron-accepting dopants in a neutral electron-donor host, stable charge-separated states are generated by hole diffusion in these blends. Furthermore, the addition of hole-trapping molecules extends the photoluminescence lifetime. By using a p-type host less reactive to oxygen and tuning 2 the donor-acceptor energy gap, our amorphous blends exhibit persistent luminescence stimulated by visible light even in air, expanding the applicability of OLPL materials. MainLong-persistent luminescence (LPL) is a phenomenon in which emission continues for a long period after photoexcitation 1 . LPL emitters are used as glow-in-the-dark paints for clock faces and emergency lights. High-efficiency LPL materials are composed of metal-oxide microcrystals and small amounts of rare-earth ions that act as chargetrapping and emission sites 2,3 . In these inorganic LPL materials, holes or electrons generated by the photoexcitation of the metal-oxide crystal are accumulated in dopants that act as charge-trapping sites. Gradual charge recombination followed by thermal detrapping produces hour-long emissions 4,5,6 . Inorganic LPL materials are insoluble in any solvent, and require grinding into microparticles before dispersion into solvents or polymers for practical applications. Most inorganic LPL systems require ultraviolet to blue excitation light below 450 nm due to the limited metal-oxide absorption bands 7,8,9 .We have reported LPL emissions from mixtures of organic molecules 10 . This organic LPL (OLPL) system can be fabricated from a solution process 11 and the fabricated films can be transparent and flexible 12 . LPL emissions can be tuned from greenish-blue to red with the addition of fluorescent materials 13 . In contrast to conventional organic roomtemperature phosphorescent (RTP) materials 14 , which store their energy in triplet excited states and exhibit radiative transition from the triplet excited states to the singlet ground states 15 , OLPL systems accumulate energy into charge-separated states similar to inorganic LPL materials. LPL and RTP can be identified from their emission decay profiles 16,17,18 .Current OLPL systems require inert gas conditions to exhibit LPL because LPL is

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confidence: 99%

Organic long-persistent luminescence stimulated by visible light in p-type systems based on organic photoredox catalyst dopants

et al. 2021

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“…In addition, as shown in Figure 6d, with the increasing thickness of the Bphen:Ag film, the full width at half‐maximum of the EL spectra of the devices S‐0, S‐1, S‐2, and S‐3 becomes larger, which may result from the shift in the exciton recombination zone caused by the imbalance of charge carrier transport. [ 48 ]…”

Section: Resultsmentioning

confidence: 99%

“…In addition, as shown in Figure 6d, with the increasing thickness of the Bphen:Ag film, the full width at half-maximum of the EL spectra of the devices S-0, S-1, S-2, and S-3 becomes larger, which may result from the shift in the exciton recombination zone caused by the imbalance of charge carrier transport. [48] As summarized in Table 1, the V on of device S-1 remains unchanged at 3.1 V compared to that of device S-0, and the maximum current efficiency (CE max ) reaches 12.96 cd/A. The brightness at 8 V increases from 6680 cd m −2 (device S-0) to 7338 cd m −2 (device S-1), while the electroluminescence (EL) spectrum changes a little.…”

Section: Electroluminescent Characteristics Of Inverted Tandem Oledsmentioning

confidence: 99%

High‐Performance Inverted Tandem OLEDs with the Charge Generation Layer based on MoO_x and Ag Doped Planar Heterojunction

Niu

Gong

et al. 2022

Advanced Optical Materials

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commercialization of OLEDs, especially for the application in lighting, [6] but it is often hard to achieve both. High brightness requires high current density, [7] and the accompanying high temperature and Coulombic force degradation will greatly shorten the lifetime. [8][9][10][11][12] Tandem configuration, by using a charge generation layer (CGL) to connect several OLED units in series, is a practical strategy to optimize the lifetime of OLEDs while maintaining high luminance. [13,14] Under the same luminance, the current of each OLED unit can be reduced in the tandem structure, which efficiently extends the lifetime of the tandem OLEDs.CGLs in tandem OLEDs can separate carriers well and inject them into adjacent functional layers, functioning as a connector between the emitting units. [15,16] At present, CGLs are commonly based on metal, conductive oxides, and transition metal oxides, such as 4,7-diphenyl-1,10-phenanthroline (Bphen):Cs 2 CO 3 , N,N′-bis-(1-naphthalenyl)-N, N′-bis-phenyl-(1,1′-biphenyl)-4,4′-diamine (NPB):MoO 3 , and Bphen:Li. [17][18][19][20][21][22][23] On the other hand, organic p-n heterojunctions can also be used as the CGL. [24][25][26] The exciton can separate at the interface of the p-n junction induced by the external electric field so that electrons from the highest occupied molecular orbital (HOMO) of the p-type material can easily inject into the lowest unoccupied molecular orbital (LUMO) of the n-type material due to the small injection barrier. [15,27] In addition, the doped n-type material will simultaneously produce a much higher electron concentration, which facilitates the electron concentration and injection. [28,29] On the other hand, doped p-type material will induce an increase in the electrical conductivity caused by a charge transfer between the dopant and the p-type material, which will lead to an increase in the free hole concentration and hole injection. [28] Therefore, the performance of the tandem OLEDs can be significantly enhanced.Compared with the traditional tandem OLEDs, the inverted tandem OLEDs can well protect the water-and oxygen-sensitive n-type layer, thus obtaining a longer lifetime.

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“…Cationic photoredox catalysts, 2,4,6-triphenylpyrylium tetra uoroborate (TPP + ) and 2,4,6tris(methoxyphenyl)pyrylium tetra uoroborate (MeOTPP + ) were used as electron acceptors [28][29][30] and semiconducting host molecules 3,3'-di(9H-carbazol-9-yl)biphenyl (mCBP) 31 and 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene (TPBi) 32 were used as electron donors (Fig. 1c).…”

Section: Resultsmentioning

confidence: 99%

Air-stable and visible-light-active p-type organic long-persistent-luminescence system by using organic photoredox catalyst

Jinnai

Kabe

Lin

et al. 2021

Preprint

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Organic long-persistent-luminescent (OLPL) materials that exhibit hour-long photoluminescence have advantages over inorganic materials, such as a sustainability, flexibility, and processability. The OLPL materials store the absorbed energy in an intermediate charge-separated state, but this charge-separated state is unstable to oxygen and does not exhibit persistent luminescence in air. The excitation wavelength of OLPL can be controlled by electron-donor and -acceptor materials, but previous materials require absorption mainly in the ultraviolet region. Here, we show OLPL systems that exhibit a persistent luminescence in air and can be excited by a wavelength from 300-nm to 600-nm. By using cationic photoredox catalysts as an electron-accepting dopant, stable charge-separated states are generated by the hole-diffusion process, as opposed to previous OLPL systems that depend on electron diffusion. By using a hole-diffusion mechanism and reducing the energy level of the lowest unoccupied molecular orbital, the OLPL system becomes stable in air and can be excited by visible light. The addition of hole-trapping material increases the LPL duration.

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The influence of the mixed host emitting layer based on the TCTA and TPBi in blue phosphorescent OLED

Cited by 23 publications

References 18 publications

Organic long-persistent luminescence stimulated by visible light in p-type systems based on organic photoredox catalyst dopants

Organic long-persistent luminescence stimulated by visible light in p-type systems based on organic photoredox catalyst dopants

High‐Performance Inverted Tandem OLEDs with the Charge Generation Layer based on MoO_x and Ag Doped Planar Heterojunction

Air-stable and visible-light-active p-type organic long-persistent-luminescence system by using organic photoredox catalyst

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The influence of the mixed host emitting layer based on the TCTA and TPBi in blue phosphorescent OLED

Cited by 23 publications

References 18 publications

Organic long-persistent luminescence stimulated by visible light in p-type systems based on organic photoredox catalyst dopants

Organic long-persistent luminescence stimulated by visible light in p-type systems based on organic photoredox catalyst dopants

High‐Performance Inverted Tandem OLEDs with the Charge Generation Layer based on MoOx and Ag Doped Planar Heterojunction

Air-stable and visible-light-active p-type organic long-persistent-luminescence system by using organic photoredox catalyst

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High‐Performance Inverted Tandem OLEDs with the Charge Generation Layer based on MoO_x and Ag Doped Planar Heterojunction