Improved electron injection into Alq3 based OLEDs using a thin lithium carbonate buffer layer

Kao, Po-Ching; Lin, Jhih-Syuan; Wang, Jing‐Yuan; Yang, Cheng‐Hsien; Chen, Sy-Hann

doi:10.1016/j.synthmet.2010.06.012

Cited by 13 publications

(3 citation statements)

References 20 publications

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“…The HOMO level of pure NPB locates at about 5.4 eV based on our previous research. 11,12 According to elucidation of other published works, [13][14][15] it can be seen that the edges of C545T and TPBi deposited NPB are about 1.4 eV and 1.7 eV below the Fermi level. The HOMO level can be calculated as 5.15 eV and 5.6 eV, respectively.…”

Section: Resultsmentioning

confidence: 88%

The Investigation of Two Different Types of Multiple-Quantum-Well Structure on Fluorescent White Organic Light Emitting Devices

Chen

Fang

et al. 2012

ECS J. Solid State Sci. Technol.

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To study the effect of multiple-quantum-well (MQW) structure on emission characteristics of white organic light-emitting diodes (WOLEDs), we fabricate trapping-type and blocking-type MQWs by inserting C545T (green dye) and TPBi, respectively, into hole transport NPB layer (ITO/CuPc/NPB/MADN:rubrene/TPBi/LiF/Al). Bright efficient and stable fluorescent white emission was obtained for the OLED with 2 trapping-type MQWs formed with C545T (thickness: 2 nm). The device current and power efficiency were greatly raised 36% (7.55 cd/A, 4.36 lm/w) relative to that of reference device (5.44 cd/A, 3.40 lm/w). Furthermore, the improvement remained even beyond the roll-off effect caused by high current density. However, the blocking-type MQW structure was difficult to optimize due to too intense blocking effect of TPBi layer. The mechanistic differences between trapping- and blocking-type MQW structures were elucidated using hole-only device and SCLC measurements. The experimental results show that trapping-type MQW structure manipulates hole transport effectively to improve charges balance which is essential in enhancing device performance, making it applicable for facile fabrication of efficient OLEDs.

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Section: Resultsmentioning

confidence: 88%

The Investigation of Two Different Types of Multiple-Quantum-Well Structure on Fluorescent White Organic Light Emitting Devices

Chen

Fang

et al. 2012

ECS J. Solid State Sci. Technol.

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“…Numerous other studies have investigated n-type metal oxide semiconductors 60 and alkali metal containing interlayers. 61,62…”

Section: Cathode and Electron Injection Layer (Eil)mentioning

confidence: 99%

Computer aided design of stable and efficient OLEDs

Paterson

May

Andrienko

2020

Journal of Applied Physics

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Organic light emitting diodes (OLEDs) offer a unique alternative to traditional display technologies. Tailored device architecture can offer properties such as flexibility and transparency, presenting unparalleled application possibilities. Commercial advancement of OLEDs is highly anticipated, and continued research is vital for improving device efficiency and lifetime. The performance of an OLED relies on an intricate balance between stability, efficiency, operational driving voltage, and color coordinates, with the aim of optimizing these parameters by employing an appropriate material design. Multiscale simulation techniques can aid with the rational design of these materials, in order to overcome existing shortcomings. For example, extensive research has focused on the emissive layer and the obstacles surrounding blue OLEDs, in particular, the trade-off between stability and efficiency, while preserving blue emission. More generally, due to the vast number of contending organic materials and with experimental pre-screening being notoriously time-consuming, a complementary in silico approach can be considerably beneficial. The ultimate goal of simulations is the prediction of device properties from chemical composition, prior to synthesis. However, various challenges must be overcome to bring this to a realization, some of which are discussed in this Perspective. Computer aided design is becoming an essential component for future OLED developments, and with the field shifting toward machine learning based approaches, in silico pre-screening is the future of material design.

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“…Recently, Kao et al used another carbonate material of Li 2 CO 3 as an electron-injection layer. They performed an X-ray and photoemission study to see a reaction mechanism between the electron-injection layer and the emission layer [8].…”

Section: Introductionmentioning

confidence: 99%

Efficiency and Lifetime Improvement of Organic Light- Emitting Diodes with a Use of Lithium-Carbonate- Incorportated Cathode Structure

Mok¹,

Kim

2012

Transactions on Electrical and Electronic Materials

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Enhancement of efficiency and luminance of organic light-emitting diodes was investigated by the introduction of a lithium carbonate (Li 2 CO 3 ) electron-injection layer. Electron-injection layer is used in organic light-emitting diodes to inject electrons efficiently between a cathode and an organic layer. A device structure of ITO/TPD (40 nm)/ Alq 3 (60 nm)/Li 2 CO 3 (x nm)/Al (100 nm) was manufactured by thermal evaporation, where the thickness of Li 2 CO 3 layer was varied from 0 to 3.3 nm. Current density-luminance-voltage characteristics of the device were measured and analyzed. When the thickness of Li 2 CO 3 layer is 0.7 nm, the current efficiency and luminance of the device at 8.0 V are improved by a factor of about 18 and 3,000 compared to the ones without the Li 2 CO 3 layer, respectively. The enhancement of efficiency and luminance of the device with an insertion of Li 2 CO 3 electron-injection layer is thought to be due to the lowering of an electron barrier height at the interface region between the cathode and the emissive layer. This is judged from an analysis of current density-voltage characteristics with a Fowler-Nordheim tunneling conduction mechanism model. In a study of lifetime of the device that depends on the thickness of Li 2 CO 3 layer, the optimum thickness of Li 2 CO 3 layer was obtained to be 1.1 nm. It is thought that an improvement in the lifetime is due to the prevention of moisture and oxygen by Li 2 CO 3 layer. Thus, from the efficiency and lifetime of the device, we have obtained the optimum thickness of Li 2 CO 3 layer to be about 1.0 nm.

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Improved electron injection into Alq3 based OLEDs using a thin lithium carbonate buffer layer

Cited by 13 publications

References 20 publications

The Investigation of Two Different Types of Multiple-Quantum-Well Structure on Fluorescent White Organic Light Emitting Devices

The Investigation of Two Different Types of Multiple-Quantum-Well Structure on Fluorescent White Organic Light Emitting Devices

Computer aided design of stable and efficient OLEDs

Efficiency and Lifetime Improvement of Organic Light- Emitting Diodes with a Use of Lithium-Carbonate- Incorportated Cathode Structure

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