Electronic Properties at Gold/Conjugated‐Polyelectrolyte Interfaces

Seo, Jung Hwa; Yang, Renqiang; Brzeziński, Jacek Z.; Walker, Bright; Bazan, Guillermo C.; Nguyen, Thuc Quyen

doi:10.1002/adma.200802420

Cited by 143 publications

(146 citation statements)

References 40 publications

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“…In a series of earlier reports it has been shown that the transient response of mobile ion possessing CPE-based PLEDs is strongly dependent on the ion size and environment (including neighboring functional groups). 9,12,13,19,29,31 The striking difference here between F8im-Br and F8imBT-Br which possess the same mobile bromide ion and imidazolium side chain tethered ionic groups represents a significant deviation from typical behavior. The low electron injection barrier for F8imBT-Br in contact with the Al electrode might also contribute to the fast transient response observed by minimizing the field dropped across the EIL.…”

Section: Resultsmentioning

confidence: 92%

“…[4][5][6][7][8][9][10] It was reported that the charged nature of CPEs has the ability to enhance polymer light-emitting diode (PLED) efficiencies as a consequence of reduction in the energy barrier for electron injection from high work function metals, much in the same way that charge trapping can, but with greater control and no requirement for pre-stressing. 11 This is understood mainly due to the formation of permanent dipoles at the CPE/metal interface 12,13 as also achieved with dipolar self-assembled monolayers (SAMs), but without their need for specific interface chemistry. 14 CPEs can also be used to improve the device performance of organic solar cells.…”

Section: Introductionmentioning

confidence: 99%

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High-Efficiency Polymer LEDs with Fast Response Times Fabricated via Selection of Electron-Injecting Conjugated Polyelectrolyte Backbone Structure

Suh

Bailey

Kim

et al. 2015

ACS Appl. Mater. Interfaces

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Imidazolium ionic side-group-containing fluorene-based conjugated polyelectrolytes (CPEs) with different π-conjugated structures, poly[(9,9-bis(8'-(3"-methyl-1"-imidazolium)octyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] dibromide (F8im-Br) and poly [(9,9-bis(8'-(3"-methyl-are synthesized and utilized as an electron injection layer (EIL) in green-emitting F8BT polymer light-emitting diodes (PLEDs). Both CPE EIL devices significantly outperform Ca cathode devices; 17.9 cd A -1 (at 3.8 V) and 16.6 lm W -1 (at 3.0 V) for F8imBT-Br devices, 11.1 cd A -1 (at 4.2 V) and 9.1 lm W -1 (at 3.4 V) for F8im-Br devices, and 7.2 cd A -1 (at 3.6 V) and 7.0 lm W -1 (at 3.0 V) for Ca devices. Importantly, unlike the F8im-Br EIL devices, F8imBT-Br PLEDs exhibit much faster electroluminescence turn-on times (< 10 μs) despite both EILs possessing the same tethered imidazolium and mobile bromide ions. The F8imBT-Br devices represent, to the best of our knowledge, the highest efficiency in thin (70 nm) single-layer F8BT PLEDs in conventional device architecture with the fastest EL response time using CPE EIL with mobile ions. Our results clearly indicate the importance of an additional factor of EIL materials, specifically the conjugated backbone structure, to determine the device efficiency and response times.3

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Section: Resultsmentioning

confidence: 92%

Section: Introductionmentioning

confidence: 99%

High-Efficiency Polymer LEDs with Fast Response Times Fabricated via Selection of Electron-Injecting Conjugated Polyelectrolyte Backbone Structure

Suh

Bailey

Kim

et al. 2015

ACS Appl. Mater. Interfaces

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“…The charged CPE electron transport layers (ETLs) are believed to lower the charge injection barrier between the high work function electrode and the active layer by creating a permanent dipole between the metal and the CPE, in addition to a migration of charged ions into the film. [11][12][13][14] Although enhanced efficiency in PLEDs has been demonstrated using CPEs, [8,15] these polymers require complicated synthesis routes. The most effective polymers have used a hole-transporting polyfluorene backbone, which could hinder their hole-blocking properties.…”

Section: Introductionmentioning

confidence: 99%

Solution processed naphthalene diimide derivative as electron transport layers for enhanced brightness and efficient polymer light emitting diodes

et al. 2013

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Increasing the efficiency and lifetime of polymer light emitting diodes (PLEDs) requires a balanced injection and flow of charges through the device, driving demand for cheap and effective electron transport/ hole blocking layers. Some materials, such as conjugated polyelectrolytes, have been identified as potential candidates but the production of these materials requires complex, and hence costly, synthesis routes. We have utilized a soluble small molecule naphthalene diimide derivative (DC18) as a novel electron transport/hole blocking layer in common PLED architectures, and compared its electronic properties to those of the electron transport/hole blocking small molecule bathocuproine (BCP). PLEDs incorporating DC18 as the electron transport layer reduce turn on voltage by 25%; increase brightness over three and a half times; and provide a full five-fold enhancement in efficiencies compared to reference devices. While DC18 has similar properties to the effective conjugated polyelectrolytes used as electron transport layers, it is simpler to synthesise, reducing cost while retaining favourable electron transport properties, and improves upon their degree for efficiency enhancement. The impact on device lifetime is hypothosized to be significant as well, due to the air-stability seen in many naphthalene diimide derivatives.

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“…Recently a polymer/oxide interface was thoroughly examined by use of multiple samples with varying thickness polymer films under the assumption that the substrate surfaces were the same for all samples. 74 Schlaf and coworkers have also performed in situ deposition of polymers via electrospray deposition to evaluate the interfacial energy alignment. 77 HAXPES is well suited to the study of a polymer/substrate interface since a single sample can be probed at varying depths.…”

Section: Haxpes Of Protected Ito Interfaces With P3htmentioning

confidence: 99%

“…7, 14, [72][73][74][75][76] Interfacial modifications and/or the presence of adventitious species have been shown to dramatically affect performance of organic electronic devices. 4,5,32 In organic photovoltaics (OPVs) and organic light emitting diodes (OLEDs) charge injection barriers can be present due to energy level offsets, and also due to the presence of undesirable chemical species at the interface.…”

Section: Haxpes Of Protected Ito Interfaces With P3htmentioning

confidence: 99%

Photoelectronic characterization of heterointerfaces.

Brumbach¹

2012

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In many devices such as solar cells, light emitting diodes, transistors, etc., the performance relies on the electronic structure at interfaces between materials within the device. The objective of this work was to perform robust characterization of hybrid (organic/inorganic) interfaces by tailoring the interfacial region for photoelectron spectroscopy. Self-assembled monolayers (SAM) were utilized to induce dipoles of various magnitudes at the interface. Additionally, SAMs of molecules with varying dipolar characteristics were mixed into spatially organized structures to systematically vary the apparent work function. Polymer thin films were characterized by depositing films of varying thicknesses on numerous substrates with and without interfacial modifications. Hard X-ray photoelectron spectroscopy (HAXPES) was performed to evaluate a buried interface between indium tin oxide (ITO), treated under various conditions, and poly(3-hexylthiophene) (P3HT). Conducting polymer films were found to be sufficiently conducting such that no significant charge redistribution in the polymer films was observed. Consequently, a further departure from uniform substrates was taken whereby electrically disconnected regions of the substrate presented ideally insulating interfacial contacts. In order to accomplish this novel strategy, interdigitated electrodes were used as the substrate. Conducting fingers of one half of the electrodes were electrically grounded while the other set of electrodes were electronically floating. This allowed for the evaluation of substrate charging on photoelectron spectra (SCOPES) in the presence of overlying semiconducting thin films. Such an experiment has never before been reported. This concept was developed out of the previous experiments on interfacial modification and thin film depositions and presents new opportunities for understanding chemical and electronic changes in a multitude of materials and interfaces. 4 ACKNOWLEDGMENTSMany people helped with various aspects of this project. I would like to thank

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Electronic Properties at Gold/Conjugated‐Polyelectrolyte Interfaces

Cited by 143 publications

References 40 publications

High-Efficiency Polymer LEDs with Fast Response Times Fabricated via Selection of Electron-Injecting Conjugated Polyelectrolyte Backbone Structure

High-Efficiency Polymer LEDs with Fast Response Times Fabricated via Selection of Electron-Injecting Conjugated Polyelectrolyte Backbone Structure

Solution processed naphthalene diimide derivative as electron transport layers for enhanced brightness and efficient polymer light emitting diodes

Photoelectronic characterization of heterointerfaces.

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