Energy transfer between organic fluorescent CBP host and blue phosphorescent FIrpic and FIrN4 guests

Tsuboi, Taijū; Murayama, Hirokazu; Yeh, S.-M.; Chen, Chin‐Ti

doi:10.1016/j.optmat.2006.06.005

Cited by 26 publications

(16 citation statements)

References 8 publications

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“…That is why such a variety of CBP film fluorescence and delayed fluorescence spectra have been recorded by others. 4,[8][9][10][11][12][13][14] So it is reasonable to assume that the quenching LE states we have observed may have resulted from CBP dissociation due to this weak C-N bond over time. However, the species formed due to such degradation are themselves unstable because of the same C-N bond, and after illumination with UV for a long enough time they photodegrade into nonemissive species, reducing the LE band emission.…”

Section: -5mentioning

confidence: 88%

“…In addition, one can also find discrepancies among various research groups' measurements of optical properties of CBP film, especially for fluorescence and delayed fluorescence spectra. 4,[8][9][10][11][12][13][14] In this work we explore and discuss very unusual absorption, fluorescence, phosphorescence, and delayed fluorescence properties of vacuum sublimed commercially available CBP, how it is affected by aging and UV light, and propose the origin of the redshifted peaks at 410 and 430 nm.…”

Section: -3mentioning

confidence: 99%

See 1 more Smart Citation

The photophysics of singlet, triplet, and degradation trap states in 4,4-N,N′-dicarbazolyl-1,1′-biphenyl

Jankus

Winscom

Monkman

2009

The Journal of Chemical Physics

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In this paper we report the results of optical characterization of 4,4-N,N′-dicarbazolyl-1,1′-biphenyl (CBP), known as a host material for phosphorescent light emitting devices. Using absorption, steady state, and time-resolved spectroscopy, we explore the singlet and triplet states in solid and solution samples of CBP. In solutions we observe two distinct short-lived states with well-resolved emission originating from individual molecule singlet states (at 365 and 380 nm) and “quenching” low energy (LE) states (at 404 and 424 nm). The latter are seen only in saturated solutions and solid samples. Both of those species have different lifetimes. After UV exposure of very concentrated degassed solution the intensities of the LE bands starts to decrease. The longer the solution is exposed to UV, the less emission is seen at 404 and 424 nm, until it is totally gone. The spectrum of the highly concentrated solution is then the same as the spectrum of dilute solution, i.e., only emission at 365 and 380 nm is present. An increase in intensities of the singlet emission peaks correlates with an increase in UV exposure time. Similar behavior is observed in evaporated CBP film. We propose that this behavior is due to chemical instability of the weak N–C bonding of carbazolyl moiety—this creates new degradational species over time which dissociate after exposure to UV. We believe this to be the reason for variation in CBP fluorescence and delayed fluorescence spectra recorded by various research groups. Further, we detected two types of very long-lived states. One of these states (higher energy) is ascribed to molecular phosphorescence emission, the other to emission from low energy triplet trap states which we relate to degradational species. We propose that triplets are more easily caught by these latter sites when their hopping rate increases, and they emit inefficiently from these lower energy sites.

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Section: -5mentioning

confidence: 88%

Section: -3mentioning

confidence: 99%

The photophysics of singlet, triplet, and degradation trap states in 4,4-N,N′-dicarbazolyl-1,1′-biphenyl

Jankus

Winscom

Monkman

2009

The Journal of Chemical Physics

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“…OLED는 자체 발광 소자로서 천연색 디스 플레이, 액정디스플레이(Liquid Crystal Display: LCD)의 배면광, 조명 등에 사용 가능한 높은 잠재 력을 가지고 있어 각광을 받으며 많은 연구가 진행 되었고 2) , 기판으로 유리 및 플라스틱 등의 다양한 기판을 적용할 수 있어 어떠한 형태로도 제작이 가 능하여 다양한 용도와 다양한 형태의 조명으로 사 용이 가능하다는 장점이 있다. 그러나 상용화를 위 해서는 발광효율, 소자의 수명 및 양산기술 등의 문 제점들을 개선해야 하는 상황이다 [3][4][5][6] . OLED 소자 의 효율을 개선하는 방법 중 한 가지는 인광 형광 체를 사용하는 것인데, 인광 OLED는 삼중항과 일 중항을 모두 발광에 사용하여 높은 효율을 얻을 수 있다 7,8) .…”

Section: 서 론unclassified

Emission Characteristics of White Organic Light-Emitting Diodes Using Micro Lens Array Film

Chun¹,

Na²,

Yang³

et al. 2013

Journal of the Korean institute of surface engineering

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We studied the emission characteristics of white phosphorescent organic light-emitting diodes (PHOLEDs), which were fabricated using a two-wavelength method. To optimize emission characteristics of white PHOLEDs, white PHOLEDs with co-doping and blue/co-doping emitting layer (EML) structures were fabricated using a host-dopant system. The total thickness of light-emitting layer was 25 nm and the dopant of blue and red was FIrpic and Bt 2 Ir(acac) in UGH3, respectively. In case of co-doping structure, applying micro lens array film showed efficiency improvement from the current efficiency 78.5 cd/A and power efficiency 40.4 lm/W to the current efficiency 131.1 cd/A and power efficiency 65 lm/W and blue / co-doping structure showed efficiency improvement from the current efficiency 43.8 cd/A and power efficiency 22 lm/ W to the current efficiency 69 cd/A and power efficiency 32 lm/W.

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“…특히, 인광 물질을 a. Corresponding author; sunghooju@daejin.ac.kr 사용한 OLED는 일중항과 삼중항의 발광을 모두 사 용할 수 있어 높은 효율을 보여주었다 [3][4][5]. 인광물 질은 100%의 내부 양자효율을 나타낼 수 있어 형광 물질과 비교하여 최대 4배의 효율을 구현할 수 있다 [6].…”

Section: 서 론 1)unclassified

Effect of Doping Profile of Blue Activator on the Emission Characteristics of White Organic Light Emitting Diodes

Lim¹,

Seo²,

Paek³

et al. 2011

Journal of the Korean Institute of Electrical and Electronic Ma

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To investigate the effect of two-emission-layer structure on the emission characteristics of the phosphorescent white organic light-emitting diodes (PHWOLEDs), the PHWOLEDs with two different emission layers, blue EML(29 nm, FIrpic-doped mCP) and red EML(1 nm, Ir(pq)2acac-doped CBP)), following host-guest system were fabricated. The bi-layered blue EML was composed of mCP:FIrpic (20 nm, 7 vol.%) and mCP:FIrpic (9 nm, 7, 10, 15, 20, and 25 vol.%, respectively). When the concentration of FIrpic was increased from 7 to 15 vol.%, light emission luminance, current efficiency, and external quantum efficiency were increased. On the contrary, when the concentration of FIrpic was increased to more than 20 vol.%, light emission luminance, current efficiency, and external quantum efficiency were decreased. The PHWOLEDs with the bi-layered blue EML structure of mCP:FIrpic (20 nm, 7 vol.%) and mCP:FIrpic (9 nm, 15 vol.%) showed current efficiency of 29.7 cd/A and external quantum efficiency (EQE) of 16.6% at 1,000 cd/㎠.

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Energy transfer between organic fluorescent CBP host and blue phosphorescent FIrpic and FIrN4 guests

Cited by 26 publications

References 8 publications

The photophysics of singlet, triplet, and degradation trap states in 4,4-N,N′-dicarbazolyl-1,1′-biphenyl

The photophysics of singlet, triplet, and degradation trap states in 4,4-N,N′-dicarbazolyl-1,1′-biphenyl

Emission Characteristics of White Organic Light-Emitting Diodes Using Micro Lens Array Film

Effect of Doping Profile of Blue Activator on the Emission Characteristics of White Organic Light Emitting Diodes

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