Highly polarized blue electroluminescence from homogeneously aligned films of poly(9,9-dioctylfluorene)

Whitehead, K. S.; Grell, Martin; Bradley, Donal D. C.; Jandke, M.; Strohriegl, Peter

doi:10.1063/1.126525

Cited by 221 publications

(193 citation statements)

References 14 publications

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“…Essa classe de polímeros, alguns dos quais estão mostrados na Figura 2, tem despertado o interesse dos estudiosos por suas propriedades elétricas e ópticas com potencial aplicação para fabricação de dispositivos emissores de luz (LEDs) [22][23][24][25][26][27][28][29][30][31][32][33] . Estes polímeros apresentam algumas propriedades interessantes para essa finalidade destacando-se, entre elas, grande estabilidade química, térmica e oxidativa 18,[34][35][36][37][38] ; alto rendimento quântico de fluorescência tanto em solução quanto no estado sólido 37,[39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57] ; possibilidade de formarem materiais líquido-cristalinos 46,58-68 com altos parâmetros de ordem e temperaturas de transição termotrópica na faixa entre 100 a 170 o C, ocorrendo entre as temperaturas de amolecimento e de decomposição térmica [69][70][71][72] . Dessas propriedades decorrem as potencialidades de aplicações dessa classe de polímeros.…”

Section: Introductionunclassified

Dispositivos poliméricos eletroluminescentes

Oliveira¹,

Cossiello²,

Atvars³

et al. 2006

Quím. Nova

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Recebido em 29/9/04; aceito em 21/6/05; publicado na web em 1/12/05 POLYMERIC LIGHT EMITTING DEVICES. Here we present an overview of electroluminescent devices that use conjugated polymers as the active media. The principal components of the devices are described and we show some examples of conjugated polymers and copolymers usually employed in polymeric light emitting devices (PLED). Some aspects of the photo and electroluminescence properties as well as of the energy transfer processes are discussed. As an example, we present some of the photophysical properties of poly(fluorene)s, a class of conjugated polymers with blue emission.Keywords: polymer; photoluminescence; electroluminescence. INTRODUÇÃOOs primeiros trabalhos sobre condução eletrônica em polímeros conjugados datam de 1970 1,2 sendo que a eletroluminescência (EL) em polímeros foi relatada pela primeira vez em 1989 3 . O uso de polímeros conjugados com um sistema de elétrons π delocalizados em dispositivos optoeletrônicos, conhecidos como OPLEDs ("Organic Polymeric Light Emission Devices"), tem crescido desde então. Na atualidade, monitores coloridos na forma de matriz ativa, fabricados com polímeros orgânicos emissores de luz (OPLEDs) estão na fronteira de serem comercializados. As razões para o sucesso dos OPLEDs devem-se às múltiplas possibilidades de estruturas químicas dos compostos possíveis, às várias possibilidades de formas de montagem dos dispositivos, aliadas à alta performance e ao menor custo de produção 4 . A tecnologia de exibição não é, entretanto, o único campo em que materiais orgânicos em geral, e poliméricos conjugados em particular, aparecem com um futuro promissor. Entre esses novos campos aparecem as novas tecnologias de células solares 5-8 , transistores 9-11 , emissores tipo laser, sistemas de armazenamento e circuitos integrados poliméricos [12][13][14][15][16][17] . O uso de materiais orgânicos, poliméricos ou não, nos vários tipos de dispositivos tem, entre suas principais vantagens, a imensa possibilidade de preparação de estruturas químicas diferentes, além de poderem ser misturados, formando sistemas com outras propriedades. Têm, entretanto, alguns problemas tecnológicos importantes ainda não resolvidos, relacionados com a menor estabilidade química quando comparados com materiais inorgânicos ou organo-metálicos. Entretanto, a possibilidade de mistura física entre componentes permitindo a obtenção de sistemas com diferentes propriedades é, sem dúvida, uma forma atraente e de custo reduzido de preparação de novos materiais. Essa flexibilidade nas formas de preparação de sistemas é particularmente interessante no caso de polímeros eletroluminescentes para os quais pequenas alterações nas rotas de síntese podem levar a materiais com diferentes estruturas e, o fato de apresentarem diferentes estruturas químicas, leva a que os materiais passem a emitir em diferentes regiões do espectro [18][19][20][21] . As diferenças nos processos sintéticos podem, também, envolver reações de copolimerização, permitindo a geração de materi...

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Section: Introductionunclassified

Dispositivos poliméricos eletroluminescentes

Oliveira¹,

Cossiello²,

Atvars³

et al. 2006

Quím. Nova

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“…18 For instance, cyanobiphenyl liquid crystals can be aligned by rubbing polyimide and thus to have dichroic ratios in absorption spectra. 19 The frequently used materials are polyacrylate, 20,21 polyfluorene, 18,[22][23][24][25][26][27][28] and their oligomer derivatives. 29 Additionally, lyotropic liquid crystals, which possess a hexagonal mesophase to solubilize the monomer and direct its electropolymerization, are utilized to prepare poly-(3,4-ethylenedioxythiophene) (PEDOT) films that replicate the texture and birefringence of the LC template.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and Characterization of Light-Emitting H-Bonded Complexes and Polymers Containing Bis(pyridyl) Emitting Acceptors

et al. 2005

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A series of bis(pyridyl) acceptor emitters are synthesized and the LC and photophysical (PL and EL) properties of their supramolecular structures, including H-bonded polymer networks and trimers, are explored. Unique mesomorphic properties may be introduced into these H-bonded complexes and polymers containing nonmesogenic acceptor emitters. In addition, the emission properties of bis(pyridyl) acceptor emitters can be adjusted by their surrounding nonphotoluminescent proton donors. Compared with pure bis(pyridyl) acceptor emitters, red-shifts of PL emission wavelengths were observed in most of the H-bonded complexes and polymers. Because of the higher acidity value of m-PC 10 BA (16) and its stronger H-bonded effect in H-bonded polymer complexes, the largest red-shift of 93 nm in λ max value of PL has occurred in the fully H-bonded polymer network p-PBBBP-OC 8 (8)/m-PC 10 BA (16) in contrast to pure emitter p-PBBBP-OC 8 (8). A very narrow full width at half-maximum (fwhm) value (38 nm) of EL spectra can be obtained in the device of H-bonded complexes blended with PVK, and a higher brightness of EL is produced at an appropriate annealing temperature.

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“…Other features (e.g., isotropy of the macroscopic mobility; propensity to charge trapping) depend strongly on the connectivity and texture (meaning here both the 'spaghetti structure' and the possible presence of inclusions or voids). There is considerable experimental evidence that the texture is important (Bloor et al 1975, Friend et al 1999, Gao et al 1999, Nguyen et al 2000, Shi et al 2000, Whitehead et al 2000. Still further features depend on electron transfer between one component and another: electrode-molecule electron transfer (injection) and molecule-molecule electron transfer (inter-molecular aspects of mobility.…”

Section: Components Of a Mesoscopic Modelmentioning

confidence: 99%

Mesoscopic modelling of conducting and semiconducting polymers

Stoneham

Ramos

2001

J. Phys.: Condens. Matter

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We present generalized Monte Carlo calculations to assess the effects of texture and related key factors on the properties of polymer-based light emitting diodes. We describe one class of mesoscopic model giving specific realizations of the polymer network. The model, with simple physically based rules, shows the effects of polymer structural order on current flow, trapping and radiative and non-radiative charge recombination within the polymer layer. Interactions between charges are included explicitly, as are image interactions with the electrodes. It is important that these Coulomb interactions are not simplified to an averaged space charge, since the local interactions can lead to effective trapping of charge, even in the absence of defective chains or impurity trapping. There proves to be an important role for trapping, in which charges are localized for times long compared with transit times. The competition between current flow, trapping and radiative and non-radiative charge recombination means that some of the trends are not intuitively obvious. For example, if radiative recombination occurs only on short polymer chains, as is the case for certain polymer systems, the internal efficiency appears to saturate for a concentration of these shorter luminescent chains of about 20-30%. As the proportion of shorter chains increases, trapping increases, whereas current efficiency decreases. Our approach provides a natural link between atomistic models of individual polymer molecules and the macroscopic descriptions of device modelling. Such mesoscopic models provide a means to design better film structures, and hence to optimize the effectiveness of new organic materials in a range of applications.

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Highly polarized blue electroluminescence from homogeneously aligned films of poly(9,9-dioctylfluorene)

Cited by 221 publications

References 14 publications

Dispositivos poliméricos eletroluminescentes

Dispositivos poliméricos eletroluminescentes

Synthesis and Characterization of Light-Emitting H-Bonded Complexes and Polymers Containing Bis(pyridyl) Emitting Acceptors

Mesoscopic modelling of conducting and semiconducting polymers

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