Photoluminescence Efficiency of Substituted Quaterthiophene Crystals

Abstract

The photoluminescence (PL) efficiency of substituted alpha-conjugated quaterthiophene crystals shows marked differences depending on crystal packing and molecular geometry. This effect is studied by evaluating the role of the intermolecular interactions and the effects of the single molecule conformation on the intersystem crossing (ISC) rate. The comparison of these calculations with absolute quantum efficiency measurements and with the experimental temperature dependence of the PL decay time, indicates that the differences in PL efficiency are not inherent to crystal packing effects but they are determined by the ISC rate.

Torsional effects on excitation energies of thiophene derivatives induced by β‐substituents: Comparison between time‐dependent density functional theory and approximated coupled cluster approaches

“…20,30,31 Because of the reduced symmetry in nonplanar oligothiophenes theoretical investigations are computationally more expensive and therefore often restricted to semi-empirical approaches. [31][32][33][34][35][36] In this work we will employ ab initio approaches to investigate ground-state geometries and absorption energies of S, S dioxygenated terthiophene and diphenylthiophene carrying hydrogen-, methyl, or phenyl-substituents on both β-position on the central thiophene ring as shown in Figure 1.…”

Thermally Induced Reversible Phase Transformations Accompanied by Emission Switching Between Different Colors of Two Aromatic‐Amine Compounds

“…[20] In addition, the molecular arrangement and relative orientation of chromophores in green crystal AA-2 and the rigid environment also should be responsible for the aggregation-induced blue-shifted emission phenomenon. [21] In conclusion, two luminescent trifluoromethyl-substituted aromatic-amine compounds have been synthesized.…”

Electronic structure of organic films in the first excited states determined using scanning tunneling spectroscopy: An experimental and theoretical study

“…Considering the number of photons impinging on the surface at a power of 1.5 mW ͑around 10 22 s −1 m −1 ͒, the average area occupied by a molecule ͑estimated at around 10 18 m −2 , but obviously heavily influenced by the packing density and crystal structure͒, and the excited state lifetime ͑Ͻ10 −6 s͒ a simple calculation gives an estimate that the number of molecules in an excited state at any one time is considerably less than 1%. At such a low percentage it might be thought any effect would be impossible to measure, but this ignores the fact that in crystalline organics the exciton moves coherently ͑incoher-ently͒ in the crystal ͑film͒ and that excitons might decay to triplets, 70,71 which have much longer decay times ͑an analogous band-gap reduction is expected for triplets͒. Therefore, in effect, the number of excited molecules can be much greater, but an exact estimation is beyond the scope of this article.…”