Highly reliable and transparent Al doped Ag cathode fabricated using thermal evaporation for transparent OLED applications

Song, Miyeon; Kim, Kwan-Soo; Yang, Hye In; Kim, Seong Keun; Kim, Jae Hyun; Han, Chang-Wook; Choi, Hyun‐Chul; Pode, Ramchandra; Kwon, Jang Hyuk

doi:10.1016/j.orgel.2019.105418

Cited by 38 publications

(14 citation statements)

References 30 publications

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“…Figure 3 a shows the transmittance and sheet resistance of the CSE in comparison with those of the previously reported transparent electrodes [ 6 , 40 – 45 ]. The proposed CSE has a higher FoM (88.74 10 −3 Ω −1 ) than those of the previously reported Al-doped Ag (Ag:Al) [ 6 ], graphene [ 40 ], Al-doped zinc oxide [ 41 ], Ag nanomesh (Ag NM) [ 42 ], CNT [ 43 ], MoO 3 /Ag/MoO 3 [ 44 ], and Ca:Ag [ 45 ]. The dashed lines indicate that the proposed CSE has a considerably higher FoM than the other transparent electrodes.…”

Section: Resultsmentioning

confidence: 97%

“…Compared to bottom-emitting OLEDs (BEOLEDs), top-emitting OLEDs (TEOLEDs) are more suited to use in display technologies and biomedical applications because they facilitate the use of nontransparent backplane technology for active-matrix OLEDs [ 3 ]. In addition, TEOLEDs offer the advantages of a high aperture ratio and high image quality, which makes them potential candidates for sunlight-readable displays such as smartphones, wrist-worn smartwatches, tablets, and automotive head-up displays [ 4 – 6 ]. However, despite the near 100% IQE of organic emitters, efficient outcoupling remains challenging because a large amount of light is trapped inside various components owing to total internal reflection at interfaces and the surface plasmon losses/absorption of metals [ 7 ].…”

Section: Introductionmentioning

confidence: 99%

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Cavity-Suppressing Electrode Integrated with Multi-Quantum Well Emitter: A Universal Approach Toward High-Performance Blue TADF Top Emission OLED

et al. 2022

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A novel device structure for thermally activated delayed fluorescence (TADF) top emission organic light-emitting diodes (TEOLEDs) that improves the viewing angle characteristics and reduces the efficiency roll-off is presented. Furthermore, we describe the design and fabrication of a cavity-suppressing electrode (CSE), Ag (12 nm)/WO3 (65 nm)/Ag (12 nm) that can be used as a transparent cathode. While the TADF-TEOLED fabricated using the CSE exhibits higher external quantum efficiency (EQE) and improved angular dependency than the device fabricated using the microcavity-based Ag electrode, it suffers from low color purity and severe efficiency roll-off. These drawbacks can be reduced by using an optimized multi-quantum well emissive layer (MQW EML). The CSE-based TADF-TEOLED with an MQW EML fabricated herein exhibits a high EQE (18.05%), high color purity (full width at half maximum ~ 59 nm), reduced efficiency roll-off (~ 46% at 1000 cd m−2), and low angular dependence. These improvements can be attributed to the synergistic effect of the CSE and MQW EML. An optimized transparent CSE improves charge injection and light outcoupling with low angular dependence, and the MQW EML effectively confines charges and excitons, thereby improving the color purity and EQE significantly. The proposed approach facilitates the optimization of multiple output characteristics of TEOLEDs for future display applications.

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Section: Resultsmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

Cavity-Suppressing Electrode Integrated with Multi-Quantum Well Emitter: A Universal Approach Toward High-Performance Blue TADF Top Emission OLED

et al. 2022

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“…Although the Mg:Ag cathode-based TEOLED with a 1:10 ratio showed higher efficiency than that with a 10:1 ratio, the stability of this electrode under the operating conditions could be a major issue for real applications. Moreover, the TEOLED that contained a thin metal alloy cathode with low-extinction-coefficient materials such as Yb, Al, and molybdenum trioxide (MoO 3 ) instead of Mg showed a performance similar to that of the Mg:Ag (10:1) cathode, but its efficiency and operating lifetime were still below the expectation [84][85][86].…”

Section: Semi-transparent Cathodementioning

confidence: 99%

Technical status of top-emission organic light-emitting diodes

Kim

Lampande

Kwon

2021

Journal of Information Display

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Top-emission organic light-emitting diodes (TEOLEDs) that contain semi-transparent metal top cathodes and highly reflective anodes have been actively researched for display applications due to their many advantages such as their high aperture ratio, good color purity, and high efficiency. In this research, the technical design of TEOLEDs used in organic light-emitting diode (OLED) displays is reviewed, covering the optical theory with the microcavity effect, optical losses, and the importance of the Purcell effect in the optical calculation. The key methodologies for addressing the high efficiency and low driving voltage of TEOLEDs are also discussed.

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“…show transparent 14 nm Ag: Al (Ag atomic dopant 4%) cathodes with a transmittance at 520 nm of 83.5% and a sheet resistance as low as 7.0 Ω/□ [7]. Chang 2 International Journal of Photoenergy (dimethyl sulfoxide) as an anode on PET substrate, and a bottom emission OLED was fabricated [12].…”

Section: Introductionmentioning

confidence: 99%

The Selection of Anode and Cathode Materials for Top Emission Organic Light-Emitting Diodes

Juang

Patel

Huang

et al. 2022

International Journal of Photoenergy

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In this study top emission organic light-emitting diodes (TE-OLED) were successfully fabricated on flexible PET/multilayer disordered silver nanonetwork (MDSN) substrate with conventional LiF/Al as a semitransparent cathode and Ag as a reflective anode. The effects of the hole injection layer, anode buffer layer, and an electron injection layer on the luminescence characteristics of TE-OLEDs were investigated. At first, the thickness of cathode Al is adjusted based upon the overall transmittance of the top-emission cathode and its conductivity. There is a high energy barrier for the hole between the work function of the anode Ag (4.2 eV) and the NPB highest occupied molecular orbital (HOMO) energy level (5.5 eV), which is not favorable for hole injection. This study tested four types of hole injection layer (HIL) materials. Finally, MoO3 was selected as an optimal HIL material, and the optimum thickness was adjusted, enabling the hole to be injected smoothly from the anode to the NPB and then to an emitting layer. The TE-OLED luminance reached 268 cd/m2. There is a high energy barrier between the work function of Ag and MoO3 HOMO (5.3 eV)—about 1.1 eV—which is still not conducive to the hole injection, so a thin layer of high work function metal Au (work function 5.1 eV) was added to the top of the anode silver, which more matches with the MoO3 energy level. It can make the hole easier to inject from the anode to MoO3 (HIL) and protect the silver from oxidation. At 8 V, the luminance is increased to 413.7 cd/m2, and the current efficiency is 0.81 cd/A. The luminance is significantly improved. An electron transport/hole blocking layer TPBi (10 nm) was added to enhance the electron transport capability and effectively block the holes with higher electron mobility and a higher HOMO energy level of TPBi. So that more holes can remain in the emitting layer and increase the chance of the electron-hole recombination to improve the luminance and current efficiency of TE-OLED. At 8 V, the luminance and current efficiency can reach 611.4 cd/m2 and 0.95 cd/A, respectively.

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Highly reliable and transparent Al doped Ag cathode fabricated using thermal evaporation for transparent OLED applications

Cited by 38 publications

References 30 publications

Cavity-Suppressing Electrode Integrated with Multi-Quantum Well Emitter: A Universal Approach Toward High-Performance Blue TADF Top Emission OLED

Cavity-Suppressing Electrode Integrated with Multi-Quantum Well Emitter: A Universal Approach Toward High-Performance Blue TADF Top Emission OLED

Technical status of top-emission organic light-emitting diodes

The Selection of Anode and Cathode Materials for Top Emission Organic Light-Emitting Diodes

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