Ether solvent treatment to improve the device performance of the organic light emitting diodes with aluminum cathode

Song, Qingxu; Song, Caixia; Zhong, Zhou; Hu, Zhanhao; Wang, Lei; Wang, Jian; Cao, Yong

doi:10.1016/j.orgel.2015.06.001

Cited by 7 publications

(2 citation statements)

References 45 publications

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“…However, at the PEO/Al interface, a dipole directed from the metal to the organic layer is observed, confirming the coordination interaction between Al and the ethylene oxide group, indicating that PEO is a good cathode interfacial material. 35,36 For PVP, an opposite dipole that increases the Al WF is found, confirmed by a slight shift in the Al 2p peak to higher binding energy (Supplementary Figure 11b). The dipole may have arisen from a weak coordinative interaction between the C-N group of PVP and the metal and/or hydrogen bonding from C = O to the oxidized surface of the metal.…”

Section: Resultsmentioning

confidence: 76%

Dipole formation at organic/metal interfaces with pre-deposited and post-deposited metal

Zhong

Zhang

et al. 2017

NPG Asia Mater

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In organic electronic devices, the interfacial dipole at organic/metal interfaces is critical in determining the carrier injection or extraction that limits the performance of the device. A novel technique to enable the direct measurement of underburied dipoles is developed and demonstrated. By tilting the shadow mask by a small angle, metal atoms diffuse into the opening slit to form an ultrathin metal layer during the evaporation process. As the ultrathin metal layer cannot screen out the dipole-induced surface work function change, the dipole strength and direction at the organic/metal interface can be revealed. It was found that the polarity of the organic material, the Fermi-level pinning and the interface morphology all play important roles in dipole formation. By comparing the energy level shifts at the organic/pre-deposited metal and organic/post-deposited metal interfaces, the dipole formed by molecular interactions could be distinguished from the dipole formed by Fermi-level pinning. NPG Asia Materials (2017) 9, e379; doi:10.1038/am.2017.56; published online 19 May 2017 INTRODUCTIONIn organic electronic devices, such as organic solar cells and organic light-emitting diodes, energy-level alignment at the organic/metal interface is critical for device performance because it determines the carrier injection barrier and device built-in voltage. 1,2 A small energylevel offset between the organic material's charge transport level and the metal's Fermi level is always favored to form an ohmic contact at the interface. Therefore, metals with low work function (WF), such as Ba, Ca, Li, Cs and Al, are popular choices for cathodes to facilitate electron injection or extraction. 3-5 However, low WF metals are intrinsically unstable. As a consequence, much effort has been made to develop electrode modification materials to enable the use of stable but high WF metals as cathodes. 6 Both inorganic materials, such as alkali-metal salts and metal oxides, and organic materials, such as organic surfactants, have been successfully applied in devices. [7][8][9][10][11][12] Through the formation of a dipole layer at the organic/metal interface, induced by the interfacial interaction, the interfacial energy-level alignment is modified, leading to a reduction in the charge injection barrier. 1,13 Various molecular structures are being examined to find the best modification materials for different devices.To select the desired interfacial material, the most common characterization is measuring the WF change on substrates of the cathode metal before and after depositing the interfacial materials on top 14,15 (Figure 1a). A reduced WF indicates that the electron injection barrier is lowered and hence can be used at the cathode. In contrast, an increased WF implies that the material can be used to enhance hole injection at the anode. The deduction is straightforward for inverted devices for which the layer deposition sequence, that is, cathode

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Section: Resultsmentioning

confidence: 76%

Dipole formation at organic/metal interfaces with pre-deposited and post-deposited metal

Zhong

Zhang

et al. 2017

NPG Asia Mater

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“…For the control device without the G0 ETL, a 70 nm PPF-SO15-DBT1 layer is used to maintain the same total device thickness. In addition, a control device that has undergone a solvent treatment, that is, spin-coating the n -C 12 H 26 on top of the PPF-SO15-DBT1 to account for the potential solvent effect, was also fabricated. − The schematic of the device structure is illustrated in Figure a. The luminous efficiency (LE)–current density ( J ) characteristics and the current density ( J )–bias ( V )–luminance ( L ) characteristics are shown in Figure b,c.…”

Section: Resultsmentioning

confidence: 99%

An Alkane-Soluble Dendrimer as Electron-Transport Layer in Polymer Light-Emitting Diodes

Zhong

Zhao

Pei

et al. 2016

ACS Appl. Mater. Interfaces

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Polymer light-emitting diodes (PLEDs) have attracted broad interest due to their solution-processable properties. It is well-known that to achieve better performance, organic light-emitting diodes require multilayer device structures. However, it is difficult to realize multilayer device structures by solution processing for PLEDs. Because most semiconducting polymers have similar solubility in common organic solvents, such as toluene, xylene, chloroform, and chlorobenzene, the deposition of multilayers can cause layers to mix together and damage each layer. Herein, a novel semiorthogonal solubility relationship was developed and demonstrated. For the first time, an alkane-soluble dendrimer is utilized as the electron-transport layer (ETL) in PLEDs via a solution-based process. With the dendrimer ETL, the external quantum efficiency increases more than threefold. This improvement in the device performance is attributed to better exciton confinement, improved exciton energy transfer, and better charge carrier balance. The semiorthogonal solubility provided by alkane offers another process dimension in PLEDs. By combining them with water/alcohol-soluble polyelectrolytes, more exquisite multilayer devices can be fabricated to achieve high device performance, and new device structures can be designed and realized.

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Effect of Al thin film thickness on morphology for OLED application

Shariatinia,

Fadavieslam

2023

Indian J Phys

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Ether solvent treatment to improve the device performance of the organic light emitting diodes with aluminum cathode

Cited by 7 publications

References 45 publications

Dipole formation at organic/metal interfaces with pre-deposited and post-deposited metal

Dipole formation at organic/metal interfaces with pre-deposited and post-deposited metal

An Alkane-Soluble Dendrimer as Electron-Transport Layer in Polymer Light-Emitting Diodes

Effect of Al thin film thickness on morphology for OLED application

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