Solution-processed small molecular electron transport layer for multilayer polymer light-emitting diodes

Liu, Zong You; Tseng, Shin Rong; Chao, Yu Chiang; Chen, Chun Yu; Meng, Hsin Fei; Horng, Sheng Fu; Wu, Youshen; Chen, Su Hua

doi:10.1016/j.synthmet.2010.12.021

Cited by 39 publications

(21 citation statements)

References 17 publications

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“…[1][2][3][4][5][6][7][8][9][10][11][12] The band alignments between the highest occupied molecular orbital (HOMO) of the EML and the ETLs facilitate hole accumulation and exciton recombination at the interface. [1][2][3][4][5][6][7][8][9][10][11][12] The electron mobilities of each ETL material are investigated by the spacecharge limited current (SCLC) method with the configuration of electron only devices (EODs) in Figure 2. [14][15][16][17] The structure of EODs for each ETL materials is as following; ITO / LiF (1.5 nm) / ETL (100 nm) / LiF (1.5 nm) / Al (100 nm).…”

Section: Resultsmentioning

confidence: 99%

“…An oxygen plasma treatment was also used to clean the substrate and increase the ITO work function. [1][2][3][4][5][6][7][8][9][10][11] After cleaning, 60-nm-thick HAT-CN and 30-nm-thick N,N-bis-(1-naphthyl)-N, N -diphenyl-1,1 -biphenyl-4,4 diamine (NPB) layers were deposited under high vacuum conditions as the HIL and HTL, respectively. A 40-nm-thich C545T-doped (1%) Alq 3 EML and various (Alq 3 , TAZ, TPBi, or BPhen) 20-nm-thick ETLs were thermally deposited under high vacuum conditions.…”

Section: Methodsmentioning

confidence: 99%

“…Organic light-emitting diodes (OLEDs) [1][2][3][4][5][6][7][8][9][10][11][12][13][14] have the potential to be employed in applications such as flat panel displays, flexible electronics, and solid-state lighting. Considerable research has been devoted to uncovering exact OLED operation mechanisms and precisely determining their electrical and optical properties.…”

mentioning

confidence: 99%

“…Considerable research has been devoted to uncovering exact OLED operation mechanisms and precisely determining their electrical and optical properties. The charge balance [1][2][3][4][5][6][7][8][9][10][11][12][13][14] is considered to be a key factor for controlling device performance, stability, and color coordinates; in a heterojunction device structure, holes in the hole transport layer (HTL) 1 are regarded as being transported too quickly, while electrons in the electron transport layer (ETL) 2 are transported too slowly, and as a result, holes simply pass through without generating excitons with the electrons in the emission layer (EML), which manifests as a low current efficiency.…”

mentioning

confidence: 99%

“…In the early stages of OLED heterostructure development, tris(8-hydroxyquinolinolato)aluminum (Alq 3 ) was used for both the EML and ETL in a single device. 2 Other materials that have been introduced for the ETL include 3-phenyl-4(10-naphthyl)-5-phenyl-1,2,4-triazole (TAZ), 5,7 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BPhen), 1,5,6 and 2-[3,5-bis(1-phenylbenzimidazol-2-yl)phenyl]-1-phenylbenzimidazole (TPBi) 5,7,8 in an effort to enhance the exiton recombination and current efficiencies by producing a higher electron mobility and adequate band alignment. The electron mobility also has the potential to control the exciton recombinationzone width in the EML.…”

mentioning

confidence: 99%

See 4 more Smart Citations

Effect of Electron Mobility of the Electron Transport Layer on Fluorescent Organic Light-Emitting Diodes

Rhee

Nam

Song

et al. 2014

ECS Solid State Letters

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The charge balance mechanism in green fluorescent organic light-emitting diodes is investigated for different electron transport layers (ETLs) and electron mobilities. Carrier accumulation and an increase in the exciton recombination probability are shown to be critical for improving the current and power efficiencies by aligning the bands at the interface between the emitting layer (EML) and ETL. The peak in the electroluminescence (EL) spectra was found to shift slightly in response to changes in the width of the emission zone and reflected the electron mobility of the ETL. Higher electron mobility resulted in a wider recombination zone in the EML that was manifested by a blue-shift of the EL peak.Organic light-emitting diodes (OLEDs) 1-14 have the potential to be employed in applications such as flat panel displays, flexible electronics, and solid-state lighting. Considerable research has been devoted to uncovering exact OLED operation mechanisms and precisely determining their electrical and optical properties. The charge balance 1-14 is considered to be a key factor for controlling device performance, stability, and color coordinates; in a heterojunction device structure, holes in the hole transport layer (HTL) 1 are regarded as being transported too quickly, while electrons in the electron transport layer (ETL) 2 are transported too slowly, and as a result, holes simply pass through without generating excitons with the electrons in the emission layer (EML), which manifests as a low current efficiency.To overcome this discordance between the hole and electrons mobilities and to improve the carrier charge balance, many researchers have investigated novel structures such as a metal oxide buffer layer, 3,4 electron or hole blocking layers, and new materials for the ETL 5,6 that have a high electron mobility. In the early stages of OLED heterostructure development, tris(8-hydroxyquinolinolato)aluminum (Alq 3 ) was used for both the EML and ETL in a single device. 2 Other materials that have been introduced for the ETL include 3-phenyl-4(10-naphthyl)-5-phenyl-1,2,4-triazole (TAZ), 5,7 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BPhen), 1,5,6 and 2-[3,5-bis(1-phenylbenzimidazol-2-yl)phenyl]-1-phenylbenzimidazole (TPBi) 5,7,8 in an effort to enhance the exiton recombination and current efficiencies by producing a higher electron mobility and adequate band alignment. The electron mobility also has the potential to control the exciton recombinationzone width in the EML. 9 Tang and Chen et al. 9 have shown that a higher hole mobility through the EML resulted in a wider recombination zone, which was beneficial for a longer device lifetime, and that the electroluminescence (EL) peak shifts when the width of the recombination zone changes. Both the higher hole mobility in the EML and the larger emission zone generate an additional contribution to the EL peak from adjacent layers such as the HTL and ETL. 9 In other work, Meerholz et al. 12 adjusted the width of the emission zone in the EML by copolymerization of the HT...

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

See 3 more Smart Citations

Effect of Electron Mobility of the Electron Transport Layer on Fluorescent Organic Light-Emitting Diodes

Rhee

Nam

Song

et al. 2014

ECS Solid State Letters

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Solution‐Processed, Alkali Metal‐Salt‐Doped, Electron‐Transport Layers for High‐Performance Phosphorescent Organic Light‐Emitting Diodes

Earmme

Jenekhe

2012

Adv Funct Materials

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High-performance, blue, phosphorescent organic light-emitting diodes (PhOLEDs) are achieved by orthogonal solution-processing of small-molecule electron-transport material doped with an alkali metal salt, including cesium carbonate (Cs 2 CO 3 ) or lithium carbonate (Li 2 CO 3 ). Blue PhOLEDs with solution-processed 4,7-diphenyl-1,10-phenanthroline (BPhen) electrontransport layer (ETL) doped with Cs 2 CO 3 show a luminous effi ciency (LE) of 35.1 cd A − 1 with an external quantum effi ciency (EQE) of 17.9%, which are two-fold higher effi ciency than a BPhen ETL without a dopant. These solution-processed blue PhOLEDs are much superior compared to devices with vacuum-deposited BPhen ETL/alkali metal salt cathode interfacial layer. Blue PhOLEDs with solution-processed 1,3,5-tris( m -pyrid-3-yl-phenyl)benzene (TmPyPB) ETL doped with Cs 2 CO 3 have a luminous effi ciency of 37.7 cd A − 1 with an EQE of 19.0%, which is the best performance observed to date in all-solution-processed blue PhOLEDs. The results show that a small-molecule ETL doped with alkali metal salt can be realized by solution-processing to enhance overall device performance. The solution-processed metal salt-doped ETLs exhibit a unique rough surface morphology that facilitates enhanced charge-injection and transport in the devices. These results demonstrate that orthogonal solution-processing of metal salt-doped electron-transport materials is a promising strategy for applications in various solution-processed multilayered organic electronic devices.BPhen:Li2CO3 0 wt% BPhen:Li2CO3 1.0 wt% BPhen:Li2CO3 2.5 wt% BPhen:Li2CO3 5.0 wt% BPhen:Li2CO3 7.5 wt% BPhen:Li2CO3 10.0 wt% Voltage [V]Adv. Funct. Mater. 2012, 22, 5126-5136

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Flexible, Wearable Organic Light‐Emitting Fibers Based on PEDOT:PSS/Ag‐Fiber Embedded Hybrid Electrodes for Large‐Area Textile Lighting

Lee

Kang

2020

Adv Materials Technologies

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Organic light emitting diodes (OLEDs), which possess wonderful device performance and mechanical robustness have been extensively explored in textile lighting applications. In this work, an ITO‐free, PEDOT:PSS/Ag‐fiber hybrid transparent conducting electrode (TCE) embedded in polymeric substrate (denoted as hybrid‐fiber TCE henceforth) for the fabrication of large‐area OLEDs is designed. The optimum hybrid‐fiber TCE with a pitch of 150 µm shows extraordinarily low sheet resistance (Rsheet = 1.3 Ω ▫−1) and exceptional mechanical flexibility, exhibiting ≈100% Rsheet retention at a bending radius of up to ≈0.5 mm. The device performance of the resulting OLEDs based on hybrid‐fiber TCEs (fiber‐OLEDs) is on‐par with that of ITO‐based OLED analogues. More fascinatingly, organic light emitting fibers (OLEFs), obtained via slitting the fiber‐OLEDs, display a maximum luminance efficiency of ≈38.2 cd A−1 and a maximum external quantum efficiency of ≈10.9%, which surpasses all previously reported results. In addition, the OLEFs are mechanically robust and able to withstand a high degree of deformation, thus can be woven into fabric matrix for smart textile application. The vacuum‐free, scalable fabrication of the high performance OLEFs demonstrated herein is significant for the development of extremely large‐area smart textile applications.

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Solution-processed small molecular electron transport layer for multilayer polymer light-emitting diodes

Cited by 39 publications

References 17 publications

Effect of Electron Mobility of the Electron Transport Layer on Fluorescent Organic Light-Emitting Diodes

Effect of Electron Mobility of the Electron Transport Layer on Fluorescent Organic Light-Emitting Diodes

Solution‐Processed, Alkali Metal‐Salt‐Doped, Electron‐Transport Layers for High‐Performance Phosphorescent Organic Light‐Emitting Diodes

Flexible, Wearable Organic Light‐Emitting Fibers Based on PEDOT:PSS/Ag‐Fiber Embedded Hybrid Electrodes for Large‐Area Textile Lighting

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