Unusual luminescence of thin vapour-deposited oligothiophene films

Gebauer, W.; Väterlein, C.; Soukopp, A.; Sokołowski, M.; Hock, Rainer; Port, H.; Bäuerle, Peter; Umbach, E.

doi:10.1016/s0379-6779(96)04917-x

Cited by 40 publications

(29 citation statements)

References 37 publications

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“…In retrospect, by inspecting the literature, we find a confirmation of this variance (see for instance Ref. [67]). Peak intensities of bands originally assigned to Franck-Condon components of the excitonic emission have random relative intensities.…”

Section: Thin Films Fluorescencesupporting

confidence: 56%

Electronic Structure and Energy Transfer in Solid α‐Sexithienyl

Taliani¹,

Biscarini²,

Muccini³

1999

Semiconducting Polymers

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Semiconducting conjugated polymers have been widely studied over the last twenty years for their unique electronic and optical properties, which fundamentally reside on the delocalized p-electron structure. In the early stages of the study of conjugated polymers it was thought that the p-conjugated backbone would provide the pathway for coherent electronic transport within the macromolecular unit. Further studies showed, however, that real polymers have a finite distribution of conjugated chain lengths and it became clear that electron transport would ultimately be limited by interchain hopping. Other trapping centers for electron transport are chemical defects of the macromolecular ensemble as well as morphological disorder of the material. It was at this stage that the use of oligomers had the first impulse and was widely considered a valuable route to the understanding of the intrinsic properties of conjugated polymers. In the early nineties the development of organic field effect transistors (FET), based on a-sexithienyl (T 6 ) by Garnier et al. [1,2] and confirmed soon after by Ostoja et al. [3] and Dodabalapur et al. [4], clearly indicated that the availability of chemically pure and ordered solids was the requisite to achieve reasonable working conditions for the FET operation. This finding opened the avenue for the development of the so-called plastic electronics. Disorder moreover is detrimental not only to electric transport but also, to a lesser extent, energy transport. Both charge and energy transport are among the basic steps in the operation of the organic light emitting diodes (OLED) [5,6]. Recombination is followed by energy transfer within the manifold of the excited electronic states leading ultimately to an exciton. The notion of excitons as lowest excitations in conjugated solids is now universally accepted since the emission of OLED is molecular in character as opposed to band-to-band radiative electron-hole recombination. Excitons in molecular crystals were extensively studied over the last decades [7,8]. Anisotropic intermolecular interactions in the ordered molecular solids were shown to allow the formation of collective Bloch electronic excitations (Frenkel excitons) in which the excitation is strongly bound to the molecular entity and therefore is called tight bound exciton as opposed to the weakly bound exciton (Wannier exciton) in inorganic semiconductors. Nevertheless, the excitonic band structure of conjugated oligomers is not known and the relative energy of the lowest singlet Semiconducting Polymers: Chemistry, Physics and Engineering. Edited by G. Hadziioannou and P. F. van Hutten

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Section: Thin Films Fluorescencesupporting

confidence: 56%

Electronic Structure and Energy Transfer in Solid α‐Sexithienyl

Taliani¹,

Biscarini²,

Muccini³

1999

Semiconducting Polymers

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“…9. With respect to the Ag͑001͒ substrate this closely relates to a ͑9,4͒ unit cell vector as arctan͑ 9 4 ͒ = 66.0°, or to a ͑9,3͒ vector with arctan͑ 9 3 ͒ = 71.6°. Based on these vectors we identify two coexisting higher-order commensurate structures as sketched in Figs.…”

Section: Discussionmentioning

confidence: 99%

“…Their monolayer growth has been investigated on various noble-metal surfaces and highly oriented graphite. 1,3,[5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] While on many oxide surfaces, with a weak molecule-substrate interaction, -conjugated molecules are found to adsorb in an upright standing configuration, 3,23,24 on metal substrates, such as Cu, Ag or Au, molecules in the first layer have been found to be flat lying. 1,6,10,13,17,25 On Ag͑110͒ and Ag͑111͒ 6T seems to adsorb into commensurate structures with the molecular axis parallel to the high-symmetry ͓001͔ and ͓110͔ direction, respectively, based on near-edge absorption fine structure ͑NEXAFS͒ and reflection high-energy electron diffration ͑RHEED͒ results.…”

Section: Introductionmentioning

confidence: 99%

Commensurate surface structures and concertedcis-trans-isomerization within ordered monolayers ofα-sexithiophene on Ag(001)

et al. 2008

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The monolayer of ␣-sexithiophene on Ag͑001͒ has been studied by scanning tunneling microscopy and low-energy electron diffraction. Upon deposition at room temperature four well-ordered and commensurate molecular structures have been identified where the molecules adsorb flat lying with their long axis parallel to the ͓110͔ and ͓110͔ high-symmetry directions. Whereas three structures consist of straight molecules in alltrans configuration, one long-range ordered structure is observed where all molecules have undergone a trans-cis isomerization process between the second and third thiophene ring.

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“…[2,3] In organic devices, charge transport and luminescence properties are clearly governed by the structural properties of the films. [4,5] Thus, molecular aggregation, packing, and orientation clearly affect the properties of such devices. For example, organic photovoltaic cells, epitaxially grown from p-conjugated cyclic molecules, exhibit an enhanced conversion efficiency for carrier generation and transport, due to a preferred molecular orientation.…”

Section: Introductionmentioning

confidence: 99%

“…[4,5] Because of the importance of the structural properties of thin organic films for device performance, supplementary investigations of the preparation and characterization of epitaxial multilayers are necessary.…”

Section: Introductionmentioning

confidence: 99%

LEED and Optical Spectroscopy Study of an Organic Epitaxial Multilayer Film

Schäfer¹,

Seidel

Fuchs

2001

Adv. Funct. Mater.

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Epitaxial multilayers of 2,9‐di(2‐hydroxyethyl)‐anthra[2,1,9‐def:6,5,10‐d′e′f′]diisoquinoline‐1,3,8,10‐tetrone (DMe‐PTCDI) were prepared on epitaxially grown phthalocyanine copper(II) complex (CuPc) multilayers on Ag(110) by molecular beam epitaxy. This work presents LEED and photoluminescence investigations of a highly ordered organic heterosystem. Four different mono‐ and multilayer structures are presented. LEED images taken during preparation of the monolayer structures show a dose‐dependent structural phase transition. Photoluminescence measurements on the heterosystem show a temperature‐dependent transition in the fluorescence spectrum, resulting in a significant intensity increase. The results are compared to a previous study of DMe‐PTCDI on Ag(110).

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Unusual luminescence of thin vapour-deposited oligothiophene films

Cited by 40 publications

References 37 publications

Electronic Structure and Energy Transfer in Solid α‐Sexithienyl

Electronic Structure and Energy Transfer in Solid α‐Sexithienyl

Commensurate surface structures and concertedcis-trans-isomerization within ordered monolayers ofα-sexithiophene on Ag(001)

LEED and Optical Spectroscopy Study of an Organic Epitaxial Multilayer Film

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