Effect of annealing of polythiophene derivative for polymer light-emitting diodes

Ahn, Taekyung; Lee, Haiwon; Han, Sien‐Ho

doi:10.1063/1.1429292

Cited by 52 publications

(34 citation statements)

References 12 publications

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“…Under the low excitation conditions with an incident beam current density of 0.4 A/cm 2 the CL spectrum (Fig. 2a, curve A) is similar to the photoluminescence spectrum previously reported [5]. The peak centered at 580 nm with a shoulder at 620 nm was attributed to the π-π* transition of the conjugated thiophene segments.…”

Section: Resultssupporting

confidence: 78%

“…Due to the exciton binding energy and the lattice relaxation [3] the luminescence energy of polythiophene is usually lower than the highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO) band gap, which is around 3.58 eV [4]. Both photoluminescence and electroluminescence spectra of the polymer usually show yelloworange luminescence [5]. Studies of the luminescence under high electron beam excitation are of interest in view of the prospects for electrically pumped laser.…”

Section: Introductionmentioning

confidence: 99%

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Electron beam induced light emission from the polythiophene derivative/ITO structure

Panin

Kang

Lee

2004

Physica Status Solidi (b)

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Light emission from a poly-[3-(2-benzotriazolo)-ethylthiophene]/indium tin oxide (PBET/ITO) structure under electron beam excitation was investigated. Two peaks at 580 nm (green) and 620 nm (orange) are observed under low excitation. An ultraviolet (UV) emission centered at 347 nm appeared under high current excitation. The ratio of the UV/green-orange band intensities increases with an increase of the current density and with a decrease of temperature. Stimulated emission and lasing from the polythiophene derivative structure are observed at high current density.

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Section: Resultssupporting

confidence: 78%

Section: Introductionmentioning

confidence: 99%

Electron beam induced light emission from the polythiophene derivative/ITO structure

Panin

Kang

Lee

2004

Physica Status Solidi (b)

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“…[23,24] Heat treatment of a polymeric thin film affects the PLED not only by improvement of interfacial adhesion [23] but also by the change of the intrinsic properties of the organic film itself. [25] Higher brightness and higher external electroluminescent quantum efficiency could be achieved this way, as reported respectively by Han, [26] Niu, [24] and Park. [23] Herein, after spin-coating, heat treatment of emissive layers at annealing temper- atures from 120 to 180°C for 10 min was performed for the white-light-emitting devices based on the PFO-R010-G018 copolymer.…”

mentioning

confidence: 72%

High‐Efficiency White‐Light Emission from a Single Copolymer: Fluorescent Blue, Green, and Red Chromophores on a Conjugated Polymer Backbone

et al. 2007

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In recent years, white polymer light-emitting diodes (WPLEDs) have received great attention because of their potential application in full-color flat-panel displays and solid-state lighting. A variety of approaches have been proposed for the realization of white emission in PLEDs.[1] One of the successful approaches in small-molecule organic light-emitting diodes (OLEDs) fabricated by thermal deposition is to use a multilayer device system consisting of two or more active layers, where each layer emits a primary color. [2,3] The highest device performance in multilayer phosphorescent OLEDs reached external quantum efficiency (QE) and power efficiency of 18.7 % and 37.6 lm W -1 , respectively, at a luminance of 500 cd m -2 with Commission Internationale de L'Éclairage (CIE) coordinates of (0.40,0.41), as reported by the Forrest group.[4]However, it is very difficult to fabricate multilayer PLEDs by solution processing because of the intermixing of different layers as a result of dissolution of the previously deposited layer. The most widely used approach for the manufacturing of PLEDs is to use the single-layer polymer blend system, [5][6][7][8][9] where the emitting layer consists of green and red emitters (small molecule or polymer) blended into a wide-gap bluelight-emitting polymer host and spin-coated onto an indium tin oxide/poly-(3,4-ethylenedioxythiophene) (ITO/PEDOT) substrate. Like most blended devices, the phase behavior of the guest and host is very sensitive to the driving voltage and the operating and shelf life; as a result, the color coordinates are not very stable. [5][6][7] Gong et al. [10] reported the first polymer multilayer white-light-emitting devices with a triplet phosphore doped into a blue-green polyfluorene host with water-soluble polyelectrolytes as the hole-transport layer (HTL) and electron-transfer layer (ETL). Recently, efforts have been made to prepare a single-component white polymeric emitter based on insufficient energy transfer, because phase segregation of chromophores can be significantly reduced by incorporating RGB (red-green-blue) chromophores into a single polymer chain. Lee et al. first reported a single fluorene-based copolymer composed of blue-, green-, and red-light-emitting units (although the RGB chromophores were not in full conjugation in the main chain) with a maximum brightness of 820 cd m -2 at 11 V with CIE coordinates of (0.33,0.35).[11] At almost the same time, Wang and co-workers adopted a slightly different synthetic strategy by which a green-emitting component was attached to the pendant chain and a red-emitting component was incorporated into the blue-emitting polyfluorene backbone.[12] The electroluminescent device exhibited a luminance efficiency of 1.59 cd A -1and CIE coordinates of (0.31,0.34). A similar strategy with two chromophores for producing white-light-emitting polymers has been reported, with a luminous efficiency (LE) of 3.8 cd A -1 and CIE coordinates of (0.32,0.36), [13] and a luminous efficiency of 7.3 cd A -1 and CIE coordinates of (0.3...

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“…Given that PBTTT dominates the crystalline domains while PCBM forms mainly the disordered domains for electron transport in the bulk-heterojunction, the postannealing should reduce the free volume and the density of defects at the interface and in the bulk volume of PBTTT to facilitate the hole transport. 35 In addition to the enhanced hole transport described above, it is essential to also improve the electron transport in order to optimize the device performance. In this context, the incorporation of a thin film of TiO x between the active layer and the Al electrode has been demonstrated to significantly improve the photovoltaic outputs of P3HT:PCBM devices.…”

Section: Resultsmentioning

confidence: 99%

Liquid Crystalline Polymers for Efficient Bilayer-Bulk-Heterojunction Solar Cells

2009

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The unique temperature-dependent solubility of liquid crystalline poly(2,5-bis(3-alkylthiophen-2-yl)thieno [3,2-b]thiophene) (PBTTT) enabled us to construct the first bilayer-bulk-heterojunction devices based on a PBTTT: PCBM (1:2)/MDMO-PPV:[70]PCBM (1:4) active layer. The bilayer device exhibited an extended optical absorption over the solar spectrum and concentration gradient that enhanced charge carrier transport. Postannealing the bilayer-bulk-heterojunction devices yielded a V oc of 0.59 V, J sc values of 10.1-10.7 mA/ cm 2 , an FF of 0.50, and PCE values of 3.0-3.2%, showing an increased J sc and PCE by a factor of 2 with respect to their single layer counterparts. This study suggests that the bilayered device structure has distinct advantages for the development of highly efficient polymer solar cells.

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Effect of annealing of polythiophene derivative for polymer light-emitting diodes

Cited by 52 publications

References 12 publications

Electron beam induced light emission from the polythiophene derivative/ITO structure

Electron beam induced light emission from the polythiophene derivative/ITO structure

High‐Efficiency White‐Light Emission from a Single Copolymer: Fluorescent Blue, Green, and Red Chromophores on a Conjugated Polymer Backbone

Liquid Crystalline Polymers for Efficient Bilayer-Bulk-Heterojunction Solar Cells

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