Solution Processing Small‐Molecule Organic Emitter in Field‐Induced, Carrier Gated Lighting Devices

Xu, Junwei; Carroll, David; Li, Peiyun; Nolan, Lorraine; Shao, Linqi; Dun, Chaochao

doi:10.1002/adom.201600917

Cited by 7 publications

(7 citation statements)

References 29 publications

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“…Since the utilization of inorganic ZnO‐gate is beneficial to reduce overheating caused by excessive hot carriers at the interfaces, Xu et al further explored tris(8‐hydroxyquinoline) aluminum (Alq 3 ) with adequate solubility as the emitters in AC‐driven organic EL devices, as shown in the inset of Figure a . The performance of the solution‐processed Alq 3 ‐based AC‐driven organic EL devices with a gate layer of ZnO for which the chloroform, acetone, and dimethyl formamide (DMF) were utilized for the dissolution of Alq 3 were investigated and compared.…”

Section: Optimizing Strategies For Ac‐driven El Devicesmentioning

confidence: 99%

“…So far, researchers have been carrying out the arduous work in simplifying the fabrication technology, optimizing the device configuration, upgrading the dielectric layers, exploiting new electrodes types and emitting nanomaterials, resulting in many inspiring advancements . However, surprisingly, there are few comprehensive review articles focusing on the flourishing development of AC‐driven EL devices, aside from one progress report involving AC‐driven OLEDs .…”

Section: Introductionmentioning

confidence: 99%

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Advances in Alternating Current Electroluminescent Devices

Wang

Lian

et al. 2019

Advanced Optical Materials

116

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radiatively at the active emissive layer driven by constant-voltage or direct current (DC). However, the DC-driven mode for OLEDs and QLEDs limits their practical applications. One reason is that the unidirectional DC flow may lead to unfavorable charges accumulation at high current density. Furthermore, the power losses are unavoidable as the DC-driven devices require power converters and rectifiers when connected to the 110/220 V at 50/60 Hz alternating current (AC) power sources. OLEDs are also particularly sensitive to dimensional variations accompanied by the generation of leakage currents at such imperfections, which is unfavorable for their application in flexible electronics. Consequently, AC-driven EL devices have attracted attention as promising alternatives to DC-driven EL devices for a variety of applications. [25][26][27][28][29][30][31][32][33] AC-driven EL devices are primarily composed of electrodes, an emissive layer and a single-or multilayer of insulating dielectric without the critical requirement for energy band matching, which facilitates their application in large-scale displays and flexible devices. [34] The device structure of AC-driven EL devices can be mainly divided into three kinds: i) AC-driven thin film electroluminescent (AC-TFEL) devices; ii) AC-driven lightemitting devices (AC-LEDs), and iii) AC-driven light-emitting field effect diodes (AC-LEFETs). Under the AC electric field, light generation is based on either the hot-electron impact excitation mechanism or the exciton recombination mechanism, depending on the device configuration. Despite the different operation principles, AC-driven EL devices have shown specific Alternating current (AC)-driven electroluminescent (EL) devices have recently attracted attention as potential alternatives to direct current (DC)-driven organic light-emitting diodes (OLEDs), as they have the great advantage of easy integration into the AC power system of 110/220 V at 50/60 Hz without complicated back-end electronics. However, the high driving voltage and low power efficiency inherent to AC-driven EL devices limit their widespread application. While researchers have made some remarkable progress in this field, the underlying causes during the development process remain to be explored. The strategies for improving the performance of AC-driven EL devices with different configurations, such as the conventional sandwiched structure and multilayer-based light-emitting devices, are summarized in this review. For example, it is crucial to enhance the effective electric field around the emitters for AC-driven thin film electroluminescent (AC-TFEL) devices, while the unbalanced generation/injection of charge carriers is the main limiting factor for the performance of AC-driven light-emitting devices (AC-LEDs). The recent advances in AC-driven EL devices, with some new configurations or new-type emitting materials, are presented by category. The challenges and opportunities for the further development of AC-driven EL devices are also discussed.

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Section: Optimizing Strategies For Ac‐driven El Devicesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Advances in Alternating Current Electroluminescent Devices

Wang

Lian

et al. 2019

Advanced Optical Materials

116

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“…[48] The light emission in AC-LEDs relies on the recombination and formation of excitons in the emitting layer; it can be concluded that the performance of an AC-driven device with the luminescence mechanism based on charge recombination depends on the formation of excitons in the emitting layer under an AC electric field. [61,62] Excitons may be generated by injecting one type of charge from the external electrode or through the frequent creation of field-induced charges within the device under a cycle of alternating voltages. Hence, the device performance of AC-driven devices with the luminescence mechanism of charge recombination depends on the impactful injection of charges with the exciton generation and charge recombination balance between the electrons and holes under the AC electric field.…”

Section: Exciton Recombination Mechanismmentioning

confidence: 99%

Alternating Current Electroluminescence for Human‐Interactive Sensing Displays

Jiang,

Lee,

Zan

et al. 2023

Advanced Materials

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The development of stimuli‐interactive displays based on alternating current (AC)‐driven electroluminescence (EL) is of great interest, owing to their simple device architectures suitable for wearable applications requiring resilient mechanical flexibility and stretchability. AC‐EL displays can serve as emerging platforms for various human‐interactive sensing displays (HISDs) where human information is electrically detected and directly visualized using EL, promoting the development of the interaction of human–machine technologies. This review provides a holistic overview of latest developments in AC‐EL displays with an emphasis on their applications for HISDs. AC‐EL displays based on exciton recombination or impact excitations of hot electrons are classified into four representative groups depending upon their device architecture: (1) displays without insulating layers, (2) displays with single insulating layers, (3) displays with double insulating layers, and (4) displays with EL materials embedded in an insulating matrix. State‐of‐the‐art AC HISDs are discussed. Furthermore, emerging stimuli‐interactive AC‐EL displays are described, followed by a discussion of scientific and engineering challenges and perspectives for future stimuli‐interactive AC‐EL displays serving as photo‐electronic human–machine interfaces.This article is protected by copyright. All rights reserved

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“…It has recently been shown that AC‐OEL devices gated by n‐type wide band gap semiconducting layers in place of the insulator layers, exhibit greater carrier manipulation and luminescent performance advantages in AC power cycles . The “model” for this improvement is rather straightforward.…”

Section: Introductionmentioning

confidence: 99%

Polymer Gating White Flexible Field‐Induced Lighting Device

Carroll

Shao

et al. 2017

Adv Materials Technologies

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It has recently been shown that AC-OEL devices gated by n-type wide band gap semiconducting layers in place of the insulator layers, exhibit greater carrier manipulation and luminescent performance advantages in AC power cycles. [9,10] The "model" for this improvement is rather straightforward. By utilizing a semiconductor gate between anode and hole generation layer(HGL), hot hole carriers are prevented from direct injection in the negative half of the AC cycle, and electron extraction in HGL is facilitated. Of course, inorganic crystalline gate materials such as ZnO, NiO, and TiO 2 have been the focus of this approach and this makes the full realization of the flexible potential of AC-OEL devices difficult.Here, we present an AC-OEL structure that utilizes a novel polymeric gate layer for efficient free carrier manipulation in high-frequency power cycles. The n-type poly [(9,Ndimethyl)-N-ethylammonium)-propyl)-2,7-fluorene)-alt-2,7-(9,9dioctylfluorene)] (PFN-Br) has been used to demonstrate passive carrier management as a gate in a highly flexible platform. This gate system has also been used in this work, to construct a high color rendering index (CRI) white light emission AC-OEL device comprised of a solution-processed single emission layer with phosphorescent emitters lightly doped into a fluorescent blue host, simultaneously emitting fluorescence and phosphorescence.To harvest triplet excitons for power-efficient white light, organic sources, metallo-organic phosphors (e.g., Pt, Os, Ir, Au, Pd, and Ru complexes) are used to achieve near 100% internal quantum efficiency. [11,12] Blue, [13,14] green, [15] and red [16] phosphorescent dopants are typically employed in a single host matrix for wide spectral output. [17] Heavy doping of these phosphors (over 5 wt%) is a common method to improve the brightness and light quality of OEL devices. But, triplet-triplet annihilation (TTA) dramatically quenches radiative excitons, or yields delayed fluorescence, and substantially diminishes the luminescent efficiency and accelerates degradation. [18,19] The low endothermic triplet transfer rate also makes it difficult to achieve high CRIs in a multiblend emission layer devices. [20] In this work, however, the optical design seems to take advantage of the integration of superior flexibility a very lowdoping recipe, and AC-driving to yield a white AC-OEL device that can bend ±90° and with a high CRI (over 81 at 2800 K). We note that in these studies little emphasis has been given to impedance matching of the driving circuit. Consequently, the maximum power efficiency measured was only 2.8 lm W −1 at 1000 cd m −2 .The development of field-induced electroluminescence (EL) devices holds great promise for the production of extremely flexible and efficient largearea light sources. Here, a novel flexible polymeric gate layer for alternating current driven organic electroluminescence (AC-OEL) devices is presented. The charge-valve mechanism of carrier manipulation in forward and reversed bias of the applied AC cycles is fully det...

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Solution Processing Small‐Molecule Organic Emitter in Field‐Induced, Carrier Gated Lighting Devices

Cited by 7 publications

References 29 publications

Advances in Alternating Current Electroluminescent Devices

Advances in Alternating Current Electroluminescent Devices

Alternating Current Electroluminescence for Human‐Interactive Sensing Displays

Polymer Gating White Flexible Field‐Induced Lighting Device

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