Candle Light‐Style Organic Light‐Emitting Diodes

Jou, Jwo‐Huei; Hsieh, Chun-Yu; Tseng, Jing-Ru; Peng, Shiang-Hau; Jou, Yung-Cheng; Hong, James H.; Shen, Shengchun; Tang, Maochun; Chen, Pin-Chu; Lin, Chia‐Hua

doi:10.1002/adfm.201203209

Cited by 119 publications

(86 citation statements)

References 60 publications

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“…For example, the hybrid WOLEDs with ultrathin red/yellow/green sequence incorporations show ultra-high CRI values of 95-96. Combining a high EQE of 19.34% and color stability, to our knowledge, this is also the first WOLED with good tradeoff among device efficiency, CRI, and color stability [1,13,14,17,18,[21][22][23][24][35][36][37][38][39][40]. Such findings can provide an effective way to achieve low-cost, high-efficiency/ CRI/color stability WOLEDs with unique and simplified …”

Section: Proposed Woleds and The Basic Principlementioning

confidence: 65%

High-efficiency/CRI/color stability warm white organic light-emitting diodes by incorporating ultrathin phosphorescence layers in a blue fluorescence layer

et al. 2017

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By incorporating ultrathin (<0.1 nm) green, yellow, and red phosphorescence layers with different sequence arrangements in a blue fluorescence layer, four unique and simplified fluorescence/phosphorescence (F/P) hybrid, white organic light-emitting diodes (WOLEDs) were obtained. All four devices realize good warm white light emission, with high color rending index (CRI) of >80, low correlated color temperature of <3600 K, and high color stability at a wide voltage range of 5 V-9 V. These hybrid WOLEDs also reveal high forward-viewing external quantum efficiencies (EQE) of 17.82%-19.34%, which are close to the theoretical value of 20%, indicating an almost complete exciton harvesting. In addition, the electroluminescence spectra of the hybrid WOLEDs can be easily improved by only changing the incorporating sequence of the ultrathin phosphorescence layers without device efficiency loss. For example, the hybrid WOLED with an incorporation sequence of ultrathin red/yellow/ green phosphorescence layers exhibits an ultra-high CRI of 96 and a high EQE of 19.34%. To the best of our knowledge, this is the first WOLED with good tradeoff among device efficiency, CRI, and color stability. The introduction of ultrathin (<0.1 nm) phosphorescence layers can also greatly reduce the consumption of phosphorescent emitters as well as simplify device structures and fabrication process, thus leading to low cost. Such a finding is very meaningful for the potential commercialization of hybrid WOLEDs.

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Section: Proposed Woleds and The Basic Principlementioning

confidence: 65%

High-efficiency/CRI/color stability warm white organic light-emitting diodes by incorporating ultrathin phosphorescence layers in a blue fluorescence layer

et al. 2017

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“…6 In addition, candle-light-style OLEDs emitting yellowish orange light have been demonstrated to be a physiologically friendly light at night. 26,27 Therefore, devices A-C are physiologically friendly light due to their relatively low intensities of blue emission.…”

Section: Resultsmentioning

confidence: 99%

Highly efficient hybrid warm white organic light-emitting diodes using a blue thermally activated delayed fluorescence emitter: exploiting the external heavy-atom effect

et al. 2015

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To attain high efficiencies in hybrid white organic light-emitting diodes (WOLEDs), mutual quenching of the fluorophors and phosphors should be minimized. Efforts have been devoted to reducing the triplet quenching of phosphors; however, the quenching of fluorophors by the external heavy-atom effect (EHA) introduced by the phosphors is often ignored. Here, we observed that conventional fluorophors and fluorophors with thermally activated delayed fluorescence (TADF) behave differently in the presence of EHA perturbers. The efficiencies of the conventional fluorophors suffer greatly from the EHA, whereas the TADF fluorophors exhibit negligible changes, which makes TADF materials ideal fluorophors for hybrid devices. WOLEDs using a blue TADF fluorophor and an orange phosphor achieve a maximum forward viewing external quantum efficiency of 19.6% and a maximum forward viewing power efficiency of 50.2 lm W 21 , among the best values for hybrid WOLEDs. This report is the first time that the EHA effect has been considered in hybrid WOLEDs and that a general strategy toward highly efficient hybrid WOLEDs with simple structures is proposed. Keywords: external heavy-atom effect; hybrid white OLEDs; thermally activated delayed fluorescence INTRODUCTION Recent conceptual advancements have led to many exciting approaches to white organic light-emitting diodes (WOLEDs). 1-4 For practical use, high efficiency and long lifetime are the most critical parameters. Blue phosphors can obtain high luminous efficiency but suffer from short lifetime, while blue fluorophors are exactly the opposite. 5,6 Efforts have been devoted to resolve the tradeoff between the high efficiency and long lifetime by combining the advantages of phosphors and fluorophors, that is, by fabricating hybrid WOLEDs with blue fluorophors and green/red or orange phosphors. [6][7][8][9] To attain high efficiencies in hybrid WOLEDs, mutual quenching of the fluorophors and phosphors should be minimized. It has been long realized that the quenching of the green and red phosphorescence by the low triplet energy fluorophors is one of the main losses of excitation energy in these devices. 6 Therefore, a 'triplet harvesting' strategy by doping a blue fluorophor and red/green phosphors in separated regions of high-triplet-energy host materials has been proposed 1,10 and is further improved by incorporating blue fluorophors with high triplet energy (T 1 ) to prevent the undesirable 'back energy transfer' from the phosphors to the blue fluorophors. 2,7,8 However, the heavy metal in the phosphors introduce an external heavy-atom effect (EHA) in the emissive layer (EML) and may lead to

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“…For example, the new solid‐state lighting system being developed for installation on the International Space Station in 2015‐2016, is designed to provide astronauts optimum visual support as well as improved sleep, circadian entrainment, and daytime alertness . In another innovative approach, Jou et al report on the development of a light‐emitting diode that mimics the spectral irradiance of candle light, which would presumably have much less impact on the circadian system if used in the evening instead of a blue‐enriched compact fluorescent light bulb.…”

Section: Future Directions—intervention and Mitigationmentioning

confidence: 99%

Breast cancer and circadian disruption from electric lighting in the modern world

Stevens

Brainard²,

Blask

et al. 2013

CA A Cancer J Clinicians

269

201

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Breast cancer is the leading cause of cancer death among women worldwide and there is only limited explanation of why. Risk is highest in the most industrialized countries but also rising rapidly in the developing world. Known risk factors account for only a portion of the incidence in the high risk populations, and there has been considerable speculation, and many false leads, on other possibly major determinants of risk such as dietary fat. A hallmark of industrialization is the increasing use of electricity to light the night, both within the home and without. It has only recently become clear that this evolutionarily new, and thereby unnatural exposure can disrupt human circadian rhythmicity, of which three salient features are melatonin production, sleep, and the circadian clock. A convergence of research in cells, rodents, and humans suggests that the health consequences of circadian disruption may be substantial. An innovative experimental model has shown that light at night markedly increases growth of human breast cancer xenografts in rats. In humans, the theory that light exposure at night increases breast cancer risk leads to specific predictions that are being tested epidemiologically: evidence has accumulated on risk in shift workers, risk in blind women, and impact of sleep duration on risk. If electric light at night does explain a portion of the breast cancer burden then there are practical interventions that can be implemented, including more selective use of light, and adoption of recent advances in lighting technology and application.

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Candle Light‐Style Organic Light‐Emitting Diodes

Cited by 119 publications

References 60 publications

High-efficiency/CRI/color stability warm white organic light-emitting diodes by incorporating ultrathin phosphorescence layers in a blue fluorescence layer

High-efficiency/CRI/color stability warm white organic light-emitting diodes by incorporating ultrathin phosphorescence layers in a blue fluorescence layer

Highly efficient hybrid warm white organic light-emitting diodes using a blue thermally activated delayed fluorescence emitter: exploiting the external heavy-atom effect

Breast cancer and circadian disruption from electric lighting in the modern world

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