Optical processes in ultrathin oligothiophene films on well-defined substrates

Gebauer, W.; Sokołowski, M.; Umbach, E.

doi:10.1016/s0301-0104(97)00255-3

Cited by 70 publications

(46 citation statements)

References 41 publications

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“…Furthermore, the (broad) absorption features observed at » 800 cm ±1 and » 2900 cm ±1 above the band origin [2,4,9] are due to vibrationally dressed excitons, located far below the strongly allowed upper Davydov component. The latter is due to an exciton almost entirely uncoupled from vibrations.…”

mentioning

confidence: 91%

“…An unusually low 0-0 intensity was originally noted by Gebauer and co-workers for aT4 deposited on Ag(111). [2,9] As pointed out by Kouki et al [2] and Hopmeier et al, [9] self-absorption alone cannot be responsible due to the very low optical density of the thin films. The theoretical absorption and emission spectra for a defect-free 5 5 aggregate are also shown in Figure 3.…”

mentioning

confidence: 94%

“…[2±7] In aT6 crystals, values ranging from 120 cm ±1 [2] to 10 000 cm ±1 [3] have been reported. Furthermore, aTn thin films and aggregates show an unusual intensity distribution in the vibronic emission bands, with a 0±0 intensity that does not fit the usual intensity distribution for a Franck±Condon (FC) progression.…”

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confidence: 99%

“…[12] In stark contrast, the mainly ac-polarized phonon replicas are not coherently enhanced and are virtually insensitive to basal plane defects. [12] Aggregate Model: The packing within an aT4 thin film is assumed to conform to that within an aT4 crystal; [2] molecular clusters of increasing size are built from the low-temperature form. [15] A view down the long molecular axes in a 5 5 aggregate is provided in the structural items inset in Figure 1.…”

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confidence: 99%

“…[2] Subsequently, more nested fullerene-like structures of inorganic compounds were fabricated, including BN and V 2 O 5 . [3] A common feature of the cage-forming materials is their anisotropic 2D layered structures, which tend to bend and eliminate dangling bonds by the intra-layer linkage.…”

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confidence: 99%

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Absorption and Emission in Quaterthienyl Thin Films

Sun

Zhen

Spano³

et al. 2003

Advanced Materials

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The salient features in the absorption and emission spectra of αT4 aggregates (see Figure) and films are fully accounted for using a model based on linear exciton–phonon coupling and structural defects. In particular, the Davydov splitting is calculated to be of the order of 1 eV, and the unusually small 0–0 emission intensity is attributed to the high sensitivity of the 0–0 intensity to basal plane structural defects.

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confidence: 91%

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confidence: 94%

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confidence: 99%

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confidence: 99%

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confidence: 99%

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Absorption and Emission in Quaterthienyl Thin Films

Sun

Zhen

Spano³

et al. 2003

Advanced Materials

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Interchain Interactions in Organic π-Conjugated Materials: Impact on Electronic Structure, Optical Response, and Charge Transport

et al. 2001

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The pioneering work of Heeger, MacDiarmid, and Shirakawa, rewarded by the 2000 Nobel Prize in Chemistry, has paved the way for the development of the fields of plastic electronics and photonics. Functional organic molecular materials and conjugated oligomers or polymers now allow the low‐cost fabrication of thin films for insertion into new generations of electronic and optoelectronic devices. The performance of these devices relies on the understanding and optimization of several complementary processes (see sketch). Our goal is to discuss, from a theoretical standpoint, the electronic structure characteristics and interfacial properties that are of importance in all these areas. The concept of interface should be taken here in the microscopic sense, i.e., molecular interactions among two or several chains/molecules (of the same or of a different nature). Specifically, we will address the impact of interchain interactions within an organic layer on the transport and optical properties. These issues will therefore be more directly related to transistor and light‐emitting diode applications; however, in all instances, the aspects related to interfacial charge or energy transfer processes will dictate the ultimate performance of a material in a given device.

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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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Optical processes in ultrathin oligothiophene films on well-defined substrates

Cited by 70 publications

References 41 publications

Absorption and Emission in Quaterthienyl Thin Films

Absorption and Emission in Quaterthienyl Thin Films

Interchain Interactions in Organic π-Conjugated Materials: Impact on Electronic Structure, Optical Response, and Charge Transport

Electronic Structure and Energy Transfer in Solid α‐Sexithienyl

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