Polymers and an Unusual Molecular Crystal with Nonlinear Optical Properties

Wudl, Fred; Allemand, P. M.; Srdanov, G.; Ni, Z.; McBranch, D.

doi:10.1021/bk-1991-0455.ch046

Cited by 106 publications

(70 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…MEH-PPV was synthesized according to literature procedures 68,69 and had an average molecular weight of 190 000 g/mol. All polymer processing, handling, and characterization were performed either in the inert atmosphere of a nitrogen dry box or under dynamic vacuum in the optical cryostat.…”

Section: Methodsmentioning

confidence: 99%

Exciton-exciton annihilation and the production of interchain species in conjugated polymer films: Comparing the ultrafast stimulated emission and photoluminescence dynamics of MEH-PPV

2004

View full text Add to dashboard Cite

Despite the enormous versatility of conjugated polymers for use in optoelectronic devices and the correspondingly large number of research studies on their photophysics, understanding of the fundamental nature of the primary photoexcitations remains highly controversial. Part of the reason for this controversy stems from the fact that the photophysics of conjugated polymer films depends sensitively on the excitation intensity, making it difficult to compare the results of different experiments such as pump-probe stimulated emission ͑SE͒ and time-resolved photoluminescence ͑PL͒, which usually are performed at excitation intensities that differ by orders of magnitude. In this paper, we present a detailed exploration of the pump-probe SE and time-resolved PL dynamics of poly͑2-methoxy 5-͓2Ј-ethylhexyloxy͔-p-phenylene vinylene͒ ͑MEH-PPV͒ films under identical excitation conditions. Using an optically triggered streak camera, we are able to simultaneously measure the PL and SE dynamics as a function of both excitation intensity and emission wavelength. Although the SE and PL dynamics of dilute MEH-PPV solutions are identical, we find that even at relatively low excitation intensities, the PL and SE dynamics of MEH-PPV films are different, uncovering the presence of an interchain excited-state absorbing species that has dynamics distinct from the intrachain exciton. The number of interchain absorbing species increases nonlinearly with excitation intensity, suggesting that interchain species are formed both directly upon photoexcitation and as a by-product of exciton-exciton annihilation ͑E-EA͒. A comparison of the emission dynamics of pristine and intentionally oxidized MEH-PPV films leads us to conclude that there are multiple types of interchain species; we propose that the directly excited interchain species are likely aggregates or excimers, while the interchain species produced by E-EA are best assigned to polaron pairs. We also find that the wavelength dependence of the SE and PL from MEH-PPV films is complex, both because energy migration leads to a dynamic redshift of the exciton emission and because the rate of E-EA is higher for hot ͑blue-emitting͒ excitons than for thermalized ͑red-emitting͒ excitons. All the results are compared in detail to previous work, providing a means to resolve many of the apparently contradictory ideas in the literature concerning the photophysics of conjugated polymer films.

show abstract

Section: Methodsmentioning

confidence: 99%

Exciton-exciton annihilation and the production of interchain species in conjugated polymer films: Comparing the ultrafast stimulated emission and photoluminescence dynamics of MEH-PPV

2004

View full text Add to dashboard Cite

show abstract

“…The synthesis is described in the literature. 18 Films of MEH-PPV in PE ͑1 wt % MEH-PPV in UHMW-PE͒ have been prepared by gel processing as described elsewhere. 19,20 Highly oriented films have been produced by mechanical stretching in a stress-strain rheometer at 110-120°C alternatively to a route, where films are stretched by hand over a hot pin.…”

Section: Methodsmentioning

confidence: 99%

Investigation of photoexcitations of conjugated polymer/fullerene composites embedded in conventional polymers

Brabec

Dyakonov

Sariciftci

et al. 1998

The Journal of Chemical Physics

View full text Add to dashboard Cite

Investigation of photoexcitations of conjugated polymer/fullerene composites embedded in conventional polymers Brabec, C.J.; Dyakonov, V.; Sariciftci, N.S.; Graupner, W.; Leising, G.; Hummelen, Jan Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. A promising approach to improve the processability of semiconducting polymers is their incorporation into host matrices formed by conventional polymers such as polyethylene ͑PE͒ or polystyrene ͑PS͒. We have characterized the linear optical properties of several guest-host systems by absorption and luminescence measurements and probed the excited states by photoinduced absorption measurements ͑PIA͒ and light induced electron spin resonance ͑LESR͒. The interesting photophysics of conjugated polymer/fullerene donor-acceptor system, showing an ultrafast photoinduced electron transfer and a metastable charge separation in the pristine state, has been investigated in such composites where the photoactive components are further embedded into a conventional polymer matrix. The composition of the blend and the relative concentration of the components are found to strongly influence the photoinduced interaction between the conjugated polymer and the fullerenes ͑C 60 and functionalized fullerenes͒. Photoinduced electron transfer between a soluble polyphenylenevinylene ͑PPV͒ derivative and C 60 is observed in a system with PS as host when the concentration of the both electroactive components is 33%. In diluted composites with PS as matrix we find strong luminescence quenching of the PPV derivative but no electron transfer upon adding C 60 . Dominant photoexcitations in these PS systems are triplet states as follows from intensity dependencies and lifetime measurements. In diluted systems with PE as matrix neither charge transfer nor luminescence quenching has been observed.

show abstract

“…4) [42], which has been extensively investigated, both for its photophysical properties and for use in LEDs. Other soluble PPV derivatives containing long alkyl and alkoxy chains (10 [43], 11 [44], 12 [45]), cholestanoxy [46] and Scheme 1.…”

Section: Organic-solvent-soluble Ppv Derivativesmentioning

confidence: 99%

The chemistry of electroluminescent organic materials

Segura¹

1998

Acta Polym.

287

200

View full text Add to dashboard Cite

Electroluminescence has been a subject of interest for several decades because of its many applications in areas such as telecommunications or information displays. Light‐emitting diodes using p‐n junctions of inorganic semiconductors have dominated the field in the last twenty years; however, efficient blue emission has only recently been achieved and inorganic semiconductors are difficult to form over large areas, making the process uneconomic. During the last decade, an explosive growth of activity in the area of organic electroluminescence has occurred in both academia and industry, stimulated by the promise of light‐emitting plastics for the fabrication of large, flexible, inexpensive and efficient screens to be used in different applications. Thus, a substantial amount of research is presently directed towards color control and improvement of manufacturability and reliability of devices in order to make their commercialization viable. A great deal of work has been carried out by physicists and materials scientists concerned with the preparation of different device structures and with the use of different techniques for device manufacture. However, all this work would not be possible without the continuous efforts of synthetic chemists to prepare materials with enhanced luminescent properties and processabilities. This article provides a review of the main types of organic materials that have been used in the fabrica‐tion of light‐emitting diodes either as emitting materials or as charge‐transport layers. Special attention will be paid to the different synthetic strategies that have been followed in order to tune the color of the emission, to increase stability of materials and to enhance their processabilities.

show abstract

Polymers and an Unusual Molecular Crystal with Nonlinear Optical Properties

Cited by 106 publications

References 0 publications

Exciton-exciton annihilation and the production of interchain species in conjugated polymer films: Comparing the ultrafast stimulated emission and photoluminescence dynamics of MEH-PPV

Exciton-exciton annihilation and the production of interchain species in conjugated polymer films: Comparing the ultrafast stimulated emission and photoluminescence dynamics of MEH-PPV

Investigation of photoexcitations of conjugated polymer/fullerene composites embedded in conventional polymers

The chemistry of electroluminescent organic materials

Contact Info

Product

Resources

About