Dispersion-model-free determination of optical constants: application to materials for organic thin film devices
| Autor: | Jonas H.-W. M. Kremer, Norbert Danz, Malte C. Gather, Michael Flämmich, Andreas Bräuer, Dirk Michaelis, Klaus Meerholz |
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| Přispěvatelé: | Publica |
| Rok vydání: | 2009 |
| Předmět: |
Materials science
reflectance business.industry Materials Science (miscellaneous) polymer Molar absorptivity Industrial and Manufacturing Engineering spectroscopic ellipsometry transmittance measurement Reflection (mathematics) Refractive index and extinction coefficient of thin film materials Optics parameter Dispersion (optics) Surface roughness OLED Optoelectronics light-emitting diode absorbing film Business and International Management Thin film business Refractive index complex |
| Zdroj: | ResearcherID |
| ISSN: | 1539-4522 |
| Popis: | We describe a method to determine the refractive index and extinction coefficient of thin film materials without prior knowledge of the film thickness and without the assumption of a dispersion model. A straightforward back calculation to the optical parameters can be performed starting from simple measurements of reflection and transmission spectra of a 100-250 nm thick supported film. The exact film thickness is found simultaneously by fulfilling the intrinsic demand of continuity of the refractive index as a function of wavelength. If both the layer and the substrate are homogeneous and isotropic media with plane and parallel interfaces, effects like surface roughness, scattering, or thickness inhomogeneities can be neglected. Then, the accuracy of the measurement is approximately 10(-2) and 10(-3) for the refractive index and the extinction coefficient, respectively. The error of the thin film thickness determination is well below 1 nm. Thus this technique is well suited to determine the input parameters for optical simulations of organic thin film devices, such as organic light-emitting diodes (OLEDs) or organic photovoltaic (OPV) cells. We apply the method to the electroluminescent polymer poly(2,5-dioctyl-p-phenylene vinylene) (PDO-PPV) and show its applicability by comparing the measured and calculated reflection and transmission spectra of OLED stacks with up to five layers. |
| Databáze: | OpenAIRE |
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