Enhanced carrier injection of organic light emitting devices using self assembled monolayer in the cathode/organic interface

Manna, Uttam; Kim, H.M.; Gowtham, M.; Yi, Junsin; Sohn, Sunyoung; Jung, Donggeun

doi:10.1016/j.tsf.2005.08.242

Cited by 15 publications

(12 citation statements)

References 19 publications

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“…an ordered two-dimensional layer of densely packed molecules) on their surface. [18][19][20][21][22][23][24][25][26] The interfacial properties of the ZnO surface can also be easily tuned by adsorption of a SAM layer; 27,28 for instance, the improvement in the efficiency of a polymer-based solar cell involving an ZnO/SAM electron transporting layer has been attributed to the reduction of the ZnO work function upon SAM treatment. 29 A lot of previous theoretical studies focused on metal/SAM interfaces to investigate in depth the molecular parameters controlling the work function shifts.…”

Section: Introductionmentioning

confidence: 99%

Work function shifts of a zinc oxide surface upon deposition of self-assembled monolayers: a theoretical insight

Cornil

Regemorter

Beljonne

et al. 2014

Phys. Chem. Chem. Phys.

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We have investigated at the theoretical Density Functional Theory level the way the work function of zinc oxide layers is affected upon deposition of self-assembled monolayers (SAMs). 4-tert-Butylpyridine (4TBP) and various benzoic acids (BA) were adsorbed on the apolar (101[combining macron]0) ZnO and used as probe systems to assess the influence of several molecular parameters. For the benzoid acids, we have investigated the impact of changing the nature of the terminal group (H, CN, OCH3) and the binding mode of the carboxylic acid (monodentate versus bidentate) on the apolar (101[combining macron]0) surface. For each system, we have quantified the contribution from the molecular core and the anchoring group as well as of the degree of surface reconstruction on the work function shift. For the benzoic acids, the structural reorganization of the surface induces a negative shift of the work function by about 0.3 ± 0.15 eV depending on the nature of the binding mode, irrespective of the nature of the terminal function. The bond-dipole potential strongly contributes to the modification of the work function, with values in the range +1.2 to +2.0 eV. In the case of 4TBP, we further characterized the influence of the degree of coverage and of co-adsorbed species (H, OH, and water molecules) on the ZnO/SAM electronic properties as well as the influence of the ZnO surface polarity by considering several models of the polar (0001) ZnO surface. The introduction of water molecules in the (un)dissociated form at full coverage on the non-polar surface only reduces the work function by 0.3-0.4 eV compared to a reference system without co-adsorbed species. Regarding the polar surface, the work function is also significantly reduced upon deposition of a single 4BTP molecule (from -1.44 eV to -1.73 eV for our model structures), with a shift similar in direction and magnitude compared to the non-polar surfaces.

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Section: Introductionmentioning

confidence: 99%

Work function shifts of a zinc oxide surface upon deposition of self-assembled monolayers: a theoretical insight

Cornil

Regemorter

Beljonne

et al. 2014

Phys. Chem. Chem. Phys.

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“…High flexibility can be attained, as the chemical structure of the anchoring group that binds to the surface, the molecular topology of the backbone, and the nature of various substituents can be modified in the design process. Improvements in performance have been demonstrated in a number of organic electronic devices incorporating SAM‐functionalized electrodes10, 13–22 and, recently, polymer‐modified electrodes 23…”

Section: Introductionmentioning

confidence: 99%

Work‐Function Modification of Au and Ag Surfaces upon Deposition of Self‐Assembled Monolayers: Influence of the Choice of the Theoretical Approach and the Thiol Decomposition Scheme

Cornil

Wood

et al. 2013

ChemPhysChem

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We have characterized theoretically the work-function modifications of the (111) surfaces of gold and silver upon deposition of self-assembled monolayers based on methanethiol and trifluoromethanethiol. A comparative analysis is made between the experimental results and those obtained from two widely used approaches based on density functional theory. The contributions to the total work-function modifications are estimated on the basis of two decomposition schemes of the thiol molecules that have been proposed in the literature. The contributions are found to differ significantly between the two approaches, as do the corresponding adsorption energies.

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“…[1][2][3] To improve the electroluminescence (EL) efficiency and color purity, much important effort has been made in optimizing the device structures. [4][5][6] Previously, multilayer device structures were widely used because most emitting materials transport only holes or only electrons. [7][8][9][10] Generally, hole injection is easier than electron injection in most EL devices.…”

Section: Introductionmentioning

confidence: 99%

“…Organic light-emitting devices (OLEDs) have attracted great interest throughout the world owing to their potential application in the next generation of full-color flat panel displays. − To improve the electroluminescence (EL) efficiency and color purity, much important effort has been made in optimizing the device structures. − Previously, multilayer device structures were widely used because most emitting materials transport only holes or only electrons. − Generally, hole injection is easier than electron injection in most EL devices. As a result, some holes inject into the electron transport layer and result in the emission of electron transport material, thus deteriorating the color purity of the device. , To confine the recombination zone of holes and electrons within the light-emitting layer (EML), a hole block layer (HBL) is often needed. − Although significant improvement has been achieved over the years, the EL mechanisms of these multilayer devices with a hole block layer are not fully understood.…”

Section: Introductionmentioning

confidence: 99%

Electroluminescence of Hole Block Material Caused by Electron Accumulation and Hole Penetration

et al. 2008

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In this study, we investigated the electroluminescence (EL) mechanisms and processes of hole block material in the multilayer devices with Eu(TTA)3phen (TTA = thenoyltrifluoroacetone, phen = 1,10-phenanthroline) doped CBP (4,4′-N,N′-dicarbazolebiphenyl) as the light-emitting layer (EML). First, the hole block ability of 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) was experimentally confirmed by comparing the EL spectra. With increasing hole injection, BCP emission emerges and increases gradually due to the increasing hole penetration from EML into the hole block layer (HBL). Interestingly, we found that BCP emission decreases gradually with decreasing electron injection, which was attributed to the decreasing electron accumulation in HBL. By analyzing the evolution of carrier distribution in EML and HBL with decreasing electron injection, we concluded that two preconditions are very important for the EL of BCP: one is the accumulation of electrons in HBL, the other is the penetration of holes from EML into HBL. In addition, we further investigated the detailed penetration processes of holes from EML into HBL, and demonstrated that the doping of Eu(TTA)3phen molecules in EML facilitates the penetration of holes because they function as ladders between CBP and BCP molecules.

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Enhanced carrier injection of organic light emitting devices using self assembled monolayer in the cathode/organic interface

Cited by 15 publications

References 19 publications

Work function shifts of a zinc oxide surface upon deposition of self-assembled monolayers: a theoretical insight

Work function shifts of a zinc oxide surface upon deposition of self-assembled monolayers: a theoretical insight

Work‐Function Modification of Au and Ag Surfaces upon Deposition of Self‐Assembled Monolayers: Influence of the Choice of the Theoretical Approach and the Thiol Decomposition Scheme

Electroluminescence of Hole Block Material Caused by Electron Accumulation and Hole Penetration

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