Determination of the optical band gap of Alq3 and its derivatives for the use in two-layer OLEDs

Duvenhage, Mart‐Mari; Ntwaeaborwa, Martin; Visser, Hendrik G.; Swarts, Pieter J.; Swarts, Jannie C.; Swart, H.C.

doi:10.1016/j.optmat.2015.01.008

Cited by 52 publications

(24 citation statements)

References 17 publications

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“…Using the “conventional” method of determining the IE of α‐NPD from UPS measurements is once more demonstrated in Figure (a) and (b), leading to a value of 4.95 eV. This is substantially too low for α‐NPD, for which the established IE is 5.3 ± 0.1 eV . Applying the fitting routine described above, we find a local work function of 4.16 eV for α‐NPD on top of the gold stripes.…”

Section: Resultsmentioning

confidence: 93%

Importance of Substrate Work Function Homogeneity for Reliable Ionization Energy Determination by Photoelectron Spectroscopy

Schultz

Amsalem

Kotadiya

et al. 2018

Physica Status Solidi (b)

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Ultraviolet photoelectron spectroscopy (UPS) is the most widely used technique to determine the ionization energy (IE) of electronic materials, as this parameter is critically important for the energy level alignment in electronic and optoelectronic devices. For organic semiconductor IE assessment, molecules are typically evaporated and polymers spin-coated onto a conductive substrate, and then measured by UPS. For substrates that possess a constant work function over large area, the determination of IE from the measured UPS data is straight forward. However, if the substrate is heterogeneous (intentionally or unintentionally) in local work function, the conventional method to determine IE yields erroneous results and a more careful data evaluation is necessary. While the secondary electron cutoff (SECO) can exhibit area-averaged values, the valence levels are split in energy according to the local work function. Here, we demonstrate the possible pitfalls of heterogeneous substrates by employing well-controlled model systems, and show how appropriate data analysis can still yield correct IE values.

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Section: Resultsmentioning

confidence: 93%

Importance of Substrate Work Function Homogeneity for Reliable Ionization Energy Determination by Photoelectron Spectroscopy

Schultz

Amsalem

Kotadiya

et al. 2018

Physica Status Solidi (b)

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“…Non-polar solvents (dioxane < THF < DCM) showed higher molar extinction coefficient (3) value than polar aprotic solvents (DMF, DMSO) and protic solvent (MeOH) ( Table 4). The optical band gap (E gap ) for compound 2 was estimated from the absorption spectrum edge using the absorption on set 52,53 (see Fig. S3 in ESI †).…”

Section: Optical Propertiesmentioning

confidence: 99%

Solvatochromism and pH effect on the emission of a triphenylimidazole-phenylacrylonitrile derivative: experimental and DFT studies

et al. 2019

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“…The cyclic voltammogram displayed an irreversible oxidation curve ascribed to the removal of electron from the conjugated system as given in the Figure (a) and (b). HOMO energy levels have been determined from cyclic voltammogram oxidation peak in accordance with the equation E HOMO =‐(I p +4.4) eV . LUMO energy levels of the series were derived from the solid state photoluminescence spectra and estimated HOMO energy level from cyclic voltammetry.…”

Section: Resultsmentioning

confidence: 99%

Multicoloured Thiophene Based AIEgens: Single Crystal Structure Elucidation, Spectral Behaviour and DFT Studies

et al. 2018

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A series of Schiff base thiophene derivatives, D1 to D9, which exhibits a phenomenon of aggregation‐induced emission enhancement (AIEE) have been synthesised and characterized by standard spectroscopic techniques. Multicoloured emission enhancement has been achieved just by introduction of electron donating and withdrawing substituent on the thiophene moiety. Few of the molecules in the series exhibited enhanced fluorescence emission intensity in solvent mixture in comparison with that observed in pure solvent supportive of AIE. Single crystal x‐ray diffraction (SCXRD) studies on selected molecules, D6 and D7 of the series revealed the existence of planar structure and a herringbone type of crystal packing arrangement. In specific, molecules D6 and D7, possesses a larger π‐π stacking distance of around 4.866 Å and 4.636 Å, which curbs all the non‐radiative pathways, in turn leading to AIEE. DFT and TDDFT calculations confirm the structural planarity supportive of SCXRD analysis and the nature of electronic transition correlating well with the experimental results.

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Determination of the optical band gap of Alq3 and its derivatives for the use in two-layer OLEDs

Cited by 52 publications

References 17 publications

Importance of Substrate Work Function Homogeneity for Reliable Ionization Energy Determination by Photoelectron Spectroscopy

Importance of Substrate Work Function Homogeneity for Reliable Ionization Energy Determination by Photoelectron Spectroscopy

Solvatochromism and pH effect on the emission of a triphenylimidazole-phenylacrylonitrile derivative: experimental and DFT studies

Multicoloured Thiophene Based AIEgens: Single Crystal Structure Elucidation, Spectral Behaviour and DFT Studies

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