Solvent and molecular weight effects on fluorescence emission of MEH-PPV

Cossiello, Rafael F.; Akcelrud, Leni; Atvars, T. D. Z.

doi:10.1590/s0103-50532005000100012

Cited by 60 publications

(63 citation statements)

References 43 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…2,3 For instance, it is well known that photoluminescence of PPV derivatives show prominent red-shift due to the enhancement of energy transfer as the π-electron delocalization increases. 4 As pointed out in an earlier work, 5 this red-shift indicates aggregation driven by π-π interactions as the conjugation length increases.…”

Section: Introductionsupporting

confidence: 61%

See 1 more Smart Citation

Photoluminescence of Solvent-Selected Fluorescent Moieties in MEH-PPV Solutions and Films

Ribeiro¹,

Camargo²,

Pereira³

et al. 2017

J. Braz. Chem. Soc.

View full text Add to dashboard Cite

In this work, we examined how photoluminescence in poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) is affected by morphology, dictated by the mode of preparation. For that, MEH-PPV dilute solutions in good and non-solvents, thick cast films with poly[methylmethacrylate] (PMMA) as inert matrix and spin-coated thin films were prepared. These systems were studied by steady-state and time-dependent fluorescence spectroscopy and electronic microscopy. Unexpected photoluminescent behavior was detected in solutions and films and it was related to different excitons modulated by MEH-PPV conformation. By semi empirical calculations we obtained the singlet and triplet state energies of an MEH-PPV model system and, from time-resolved fluorescence spectroscopy, the existence of short-lived excited states was revealed, enabling us to infer on possible singlet fission in MEH-PPV-based systems.Keywords: photoluminescence, morphology, thin films, time-resolved fluorescence, computational calculations IntroductionSince poly(phenylene-vinylene) (PPV) derivatives were found to be electroluminescent, 1 the search for a systematic method to determine their applications has been of great interest. Their mechanical, morphological and optical properties have been widely discussed and findings related these properties to preparation methods. Although there are many aspects regarding the effects of preparation methods on optical response, authors seem to agree that preparation method influences molecular conformation, enabling or inhibiting aggregation and, consequently, affecting inter and intrachain interactions. Processing parameters are believed to modify the conformation and assembling mechanisms of polymeric materials, resulting in a memory effect of the structural information that is replicated from solutions to solid films. Therefore, to understand the role of chain conformation in solution is of major importance for applications such as device fabrication, since properties can be tuned, enhancing the desired characteristics and suppressing the undesired ones. 2,3 For instance, it is well known that photoluminescence of PPV derivatives show prominent red-shift due to the enhancement of energy transfer as the π-electron delocalization increases. 4 As pointed out in an earlier work, 5 this red-shift indicates aggregation driven by π-π interactions as the conjugation length increases.In polymeric systems, several occurrences are responsible for chain torsions that impose limits to the length of conjugated segments, affecting the highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) energy gaps. They are interpreted as stabilization and/or destabilization of HOMO and LUMO levels. 6 These occurrences may be related to the presence of impurities, molecules of solvent that strongly interact with the polymer chains and a distribution of torsion angles promoted by molecular interactions of any nature. 6 In this situation, the densities of excited states (DOS) available for electronic chan...

show abstract

Section: Introductionsupporting

confidence: 61%

“…5,42,[63][64][65][66] In the PMMA blend, the MEH-PPV fluorescence blue-shifts are related to the suppress of interchain excitons formation, 67 or to conformational changes on the polymer backbone.…”

Section: Fluorescence Of Thin Films and Blendsmentioning

confidence: 99%

Photoluminescence of Solvent-Selected Fluorescent Moieties in MEH-PPV Solutions and Films

Ribeiro¹,

Camargo²,

Pereira³

et al. 2017

J. Braz. Chem. Soc.

View full text Add to dashboard Cite

show abstract

“…Tem havido uma grande controvérsia na literatura sobre a possibilidade de agregação de polímeros conjugados, principalmente aqueles com substituintes nas posições 9 no caso dos poli(fluorenos). Entretanto, diversos trabalhos recentes demonstraram, inequivocamente, que a agregação existe e que é responsável pelas diferenças espectrais e fotofísicas [19][20][21][129][130][131] . Umas das formas de se acompanhar o processo de agregação é através da obtenção dos espectros (absorção, excitação e emissão) em soluções em diferentes concentrações.…”

Section: Propriedades Fotofísicas Dos Polímeros Eletroluminescentesunclassified

“…Freqüentemente é o processo dominante em processos de transferência de energia em soluções diluídas. Tanto em um mecanismo quanto no outro, os dados a serem analisados são os mesmos, mas as conclusões a serem obtidas são diferentes 106,123,[128][129][130][131][132][133][134][135][136][137][138][139][140][141] . No caso da transferência radiativa pode ocorrer auto-absorção e reemissão por parte do receptor e distorções no espectro de emissão do doador, sendo este último um parâmetro importante para distinguir o processo trivial do processo via Förster.…”

Section: Transferência De Energia Radiativaunclassified

Dispositivos poliméricos eletroluminescentes

Oliveira¹,

Cossiello²,

Atvars³

et al. 2006

Quím. Nova

View full text Add to dashboard Cite

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...

show abstract

“…The SAXS data for M-PPV100, in dilute solutions of xylene (non-polar) and THF (polar), are shown in properties [5]. For example, the absorption peak shows a red-shift as the conjugation length increases; also the PL drifts to longer conjugation lengths before the radiative relaxation decay [23,24].…”

mentioning

confidence: 99%

π-conjugation and conformation in a semiconducting polymer: small angle x-ray scattering study

Choudhury¹,

Bagchi²,

Menon³

2009

J. Phys.: Condens. Matter

View full text Add to dashboard Cite

Moreover, a pronounced second peak in the pair distribution function has been observed in fully conjugated chain, at larger length scales. This feature indicates that the chain segments tend to self-assemble as the conjugation along the chain increases. Xylene enhances the rigidity of PPV backbone to yield extended structures, while tetrahydrofuran solvates the side groups to form compact coils in which the l p is much shorter.

show abstract

Solvent and molecular weight effects on fluorescence emission of MEH-PPV

Cited by 60 publications

References 43 publications

Photoluminescence of Solvent-Selected Fluorescent Moieties in MEH-PPV Solutions and Films

Photoluminescence of Solvent-Selected Fluorescent Moieties in MEH-PPV Solutions and Films

Dispositivos poliméricos eletroluminescentes

π-conjugation and conformation in a semiconducting polymer: small angle x-ray scattering study

Contact Info

Product

Resources

About