Uniaxial anisotropy of organic thin films determined by ellipsometry

Heinemeyer, U.; Hinderhofer, Alexander; Alonso, M. I.; Ossó, J. O.; Garriga, M.; Kytka, M.; Gerlach, Alexander; Schreiber, Frank

doi:10.1002/pssa.200777765

Cited by 20 publications

(28 citation statements)

References 19 publications

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“…The morphology and the crystal structure of the active layer is crucially important for the efficiency of organic photovoltaic cells. The orientation of the molecules in the film determines the coupling strength of the transition dipole to the incoming light and hence strongly affects the absorption of the active layer [51,52]. The crystal structure and the defect density in the organic films strongly influence the exciton diffusion length and also the charge transport properties of the films, which are vital for the efficiency of the photovoltaic cell.…”

Section: Interface Morphology and Mixing Behaviourmentioning

confidence: 99%

Charge Separation at Nanostructured Molecular Donor–Acceptor Interfaces

Opitz

Banerjee

Grob

et al. 2016

Elementary Processes in Organic Photovoltaics

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Section: Interface Morphology and Mixing Behaviourmentioning

confidence: 99%

Charge Separation at Nanostructured Molecular Donor–Acceptor Interfaces

Opitz

Banerjee

Grob

et al. 2016

Elementary Processes in Organic Photovoltaics

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“…As it is known from the literature [36][37][38] VASE data are not very sensitive to uniaxial anisotropy on native oxide which could be confirmed by our own measurements. 31 In order to increase the sensitivity, a multiple sample analysis was performed, where the optical functions for the DIP films on both substrates, Si with native and with thermal oxide, are coupled to be the same. This is a reasonable assumption since both films were grown simultaneously and additional AFM pictures did not show any differences in morphology.…”

Section: ͒ R P R Smentioning

confidence: 99%

Exciton-phonon coupling in diindenoperylene thin films

et al. 2008

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We investigate exciton-phonon coupling and exciton transfer in diindenoperylene ͑DIP͒ thin films on oxidized Si substrates by analyzing the dielectric function determined by variable-angle spectroscopic ellipsometry. Since the molecules in the thin-film phase form crystallites that are randomly oriented azimuthally and highly oriented along the surface normal, DIP films exhibit strongly anisotropic optical properties with uniaxial symmetry. This anisotropy can be determined by multiple sample analysis. The thin-film spectrum is compared with a monomer spectrum in solution, which reveals similar vibronic subbands and a Huang-Rhys parameter of S Ϸ 0.87 for an effective internal vibration at ប eff = 0.17 eV. However, employing these parameters the observed dielectric function of the DIP films cannot be described by a pure Frenkel exciton model, and the inclusion of charge-transfer ͑CT͒ states becomes mandatory. A model Hamiltonian is parametrized with density-functional theory calculations of single DIP molecules and molecule pairs in the stacking geometry of the thin-film phase, revealing the vibronic coupling constants of DIP in its excited and charged states together with electron and hole transfer integrals along the stack. From a fit of the model calculation to the observed dielectric tensor, we find the lowest CT transition E 00 CT at 0.26Ϯ 0.05 eV above the neutral molecular excitation energy E 00 F , which is an important parameter for device applications.

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“…Besides, Heinemeyer et al (2008) utilized MSA to focus on uniaxial anisotropy of organic thin films, while other research groups have reported optical constants for silicon and thermally grown silicon oxide over the energy range of 0.75-6.5 eV (Herzinger et al, 1998), band gaps for W oxides and Ni oxides (Valyukh et al, 2009) and optical properties evaluation for the fluorocarbon films plasma deposited on silicon substrates (Easwarakhanthan et al, 2007). In this study, we aim to study the morphology of different PMMA thin films with different thicknesses deposited by spin coating on silicon substrates.…”

Section: Introductionmentioning

confidence: 99%

Morphology and Spectroscopic Ellipsometry of PMMA Thin Films

El-Nasser¹

2017

APR

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The morphology and optical properties of PMMA thin films deposited on silicon substrates were investigated. The spin coated films were characterized by atomic force microscopy and spectroscopic ellipsometry. Regardless that, the samples were deposited at different coating speeds, the surface structures of all PMMA thin films were consistent, and found to be relatively smooth, with a mean grain size in the range of 13-25 nm. The refractive index as well as the extinction coefficient of the films was determined using spectroscopic ellipsometry data over the wavelength range 380-750 nm. For this purpose, we used the Cauchy dispersion relation in order to represent PMMA layers, and then models were built by adding a roughness layer, which simply corrects any possible deviation from planarity. Besides, the thicknesses of all four films were calculated simultaneously based on multiple sample analysis method. By using this method, optical properties were coupled in such way that, the optical constants for all samples were assumed to be identical.

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Uniaxial anisotropy of organic thin films determined by ellipsometry

Cited by 20 publications

References 19 publications

Charge Separation at Nanostructured Molecular Donor–Acceptor Interfaces

Charge Separation at Nanostructured Molecular Donor–Acceptor Interfaces

Exciton-phonon coupling in diindenoperylene thin films

Morphology and Spectroscopic Ellipsometry of PMMA Thin Films

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