wKoopman's oligothiophene [10 articles]

Abstract

We use inverse photoelectron spectroscopy (IPES) and ultraviolet photoelectron spectroscopy (UPS) to investigate unoccupied and occupied electronic states of five organic semiconductor materials: CuPc (copper phthalocyanine), PTCDA (3,4,9,10-perylenetetracarboxylic dianhydride), α -6T ( α -sexithiophene), α-NPD (N,N′-diphenyl-N,N′-bis(l-naphthyl)-l,l′ biphenyl-4,4′′ diamine), and Alq 3 (tris(8-hydroxy-quinoline)aluminum). The transport gap, E t , is the difference between the highest occupied and lowest unoccupied molecular orbitals, measured via UPS and IPES. The charge separation energy, or exciton binding energy, is the difference ...

Abstract

Energetic positions of singlet and triplet states of small [small alpha]-oligothiophenes with n=2, 3 and 4 monomer units were measured by photodetachment photoelectron spectroscopy (PD-PES), phosphorescence and time resolved pump-probe spectroscopy. The triplet energy of T1 and T2 were determined experimentally for the first time in the gas phase. The triplet manifold could be extended including the levels observed by triplet-triplet absorption. The transition energies of singlet and triplet states decrease with increasing size n of the oligothiophenes following the extended ...

Abstract

Interchain interactions in organic conjugated solids causes a splitting of the lowest excited electronic states which depends on the relative packing of the chromophores and on the conjugation length. The splitting (also known as Davydov splitting) was measured for the first time in a model compound (α-sexithienyl); but the question remained open on how the Davydov splitting depends on the conjugation length. This question is particularly important because the relative location of the excitonic components plays a major role in determining ...

Abstract

We have studied photoluminescence (PL) from sublimed films of α-sexithienyl (T6) in order to understand the nature of the excited species which give rise to radiative emission. Temperature-dependent measurements of the PL spectra show an apparent 530 cm-1 blue shift of the emission as the sample temperature decreases, and the integrated PL intensity at 50 K is 1 order of magnitude larger than that at 300 K. Time-resolved PL spectra (at 10 K) indicate a fast energy transfer of excitons to ...

Note (first note only)

Cited By (since 1996): 21

Abstract

The optical properties of thin films of α,ω-dihexyl-quaterthiophene grown by organic molecular beam deposition on different substrates are illustrated. Vibronic transitions in both the absorption and the emission spectra are observed, which originate from the coupling between vibronic states in the solid, similarly as in unsubstituted quaterthiophene films. Nevertheless, the alkyl chains in α,ω-dihexyl-quaterthiophene are responsible for a shift in both the absorption and emission peaks with respect to unsubstituted quaterthiophene and for an increased mesoscopic disorder. ...

Abstract

This first concise handbook on this important new class of organic conducting materials gives a broad survey over this emerging field of research. The physical background is covered as well as the synthesis, electronic and nonlinear optical properties and applications of these advanced materials. This information will be of high value for graduate students, researchers and practitioners working in the interdisciplinary field of materials science, polymer and organic chemistry and applied physics. ...

Abstract

A series of thiophene-based oligomers are investigated by electroabsorption spectroscopy in terms of influence of chain length and peripheral substitution for the first time. Polycrystalline thin films of nonsubstituted oligomers, 8T, 6T and 4T, and of oligothiophenes with electron-withdrawing cyano substituents, 4T-V(CN) 2 and CN-TET-CN, are measured and analyzed to determine the character of optical transitions. The results of the nonsubstituted oligomers suggest that the transitions at 500–600 nm present a neutral (Frenkel exciton) character, while those of oligothiophenes with electron-withdrawing ...