Characterization of amorphous organic thin films, determination of precise model for spectroscopic ellipsometry measurements

Farahzadi, Azadeh; Beigmohamadi, Maryam; Niyamakom, Phenwisa; Kremers, Stephan; Meyer, Nico; Heuken, M.; Wuttig, Matthias

doi:10.1016/j.apsusc.2010.04.057

Cited by 9 publications

(8 citation statements)

References 15 publications

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“…The onset of absorption defined by the minimum energy value, where k differs from zero appears in the wavelength of 380 nm (¼3.26 eV) in the UV absorption band. This is on behalf of the lower limit of the optical gap for Alq 3 organic semiconductor and is in accordance with previously reported values of 2.65 [29] and 2.64 eV [30] . On the other hand, the impurity absorption peak in the near infrared band is derived from the impurity energy level induced by the Al in sample.…”

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confidence: 93%

Investigation on optical and photoluminescence properties of organic semiconductor Al-Alq3 thin films for organic light-emitting diodes application

et al. 2017

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The optical constants, photoluminescence properties, and resistivity of Al-Alq 3 thin films prepared by the thermal co-evaporation method on a silicon substrate are studied with various Al fractions. A variable angle spectroscopic ellipsometry is employed to determine the optical constants in the wavelength from 300 to 1200 nm at incidence angles of 65°, 70°, and 75°, respectively. Both the refractive indices and extinction coefficient apparently increase with increasing Al fractions. The intensity of photoluminescence spectra gradually increases with decreasing Al fractions due to intrinsic energy level transition of Alq 3 organic semiconductor in the ultraviolet wave band. The resistivity decreases from 42.1 to 3.36 Ω•cm with increasing Al fraction from 40% to 70%, resulting in a larger emission intensity in photoluminescence spectra for the 40% Al fraction sample.

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confidence: 93%

Investigation on optical and photoluminescence properties of organic semiconductor Al-Alq3 thin films for organic light-emitting diodes application

et al. 2017

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“…In this paper, we calculated the densities of organic thin films according to Xiang et al’s method and X-ray reflectometry (XRR) analysis. − The X-ray reflectometry (XRR) analysis has been used to investigate the properties of thin polymer films over recent decades. , XRR enables the determination of film density, thickness, and surface roughness. However, the study about the application of the X-ray reflectivity technique in analyzing the density measurement of small molecular thin films is relatively scarce . The density data obtained via the two approaches are shown in Table .…”

Section: Resultsmentioning

confidence: 99%

“…However, the study about the application of the X-ray reflectivity technique in analyzing the density measurement of small molecular thin films is relatively scarce. 27 The density data obtained via the two approaches are shown in Table 2. From this table, it is noted that the densities of spin-coated films are a little higher than that of the vacuum-deposited films.…”

Section: Densities Of Filmsmentioning

confidence: 99%

A Comparison Study of the Organic Small Molecular Thin Films Prepared by Solution Process and Vacuum Deposition: Roughness, Hydrophilicity, Absorption, Photoluminescence, Density, Mobility, and Electroluminescence

et al. 2011

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In this work, we report a systematic study of the properties of the solution-processed organic small molecular thin films in order to get an in-depth understanding of the distinctive nature of solution-processed thin films. N,N′-Di(3-methylphenyl)-N,N′-diphenyl-(1,1′-biphenyl)-4,4-diamine (TPD), a typical hole-transporting compound, was chosen to fabricate films by both solution process and vacuum deposition. The comparison study between the two kinds of TPD films shows that the surface of the solution-processed TPD films is more smooth and hydrophilic than that of the vacuum-deposited film. In addition, the density of the TPD films was measured by two different methods, and an increase in density was observed in solution-processed films in comparison with the vacuum-deposited film. The space-charge-limited current (SCLC) measurements indicate an increased hole transport mobility of the solution-processed TPD films over that of the vacuum-deposited film, which may result from the more compact intermolecular stacking in solution-processed TPD films. Finally, the light-emitting diodes with a solution-processed TPD layer as the hole-transport layer were fabricated and showed significantly enhanced injected current density and higher luminance relative to the device using the vacuum-deposited TPD film.

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“…One development is in the field of organic electronics, where devices such as OLEDs often use vapor-deposited glasses as electron and hole transport layers. Yokoyama et al − and others − have shown that vapor deposition can result in anisotropic films in which elongated molecules either tend to stand up or lie down, depending upon substrate temperature. For some systems, a factor of 10 change in the charge mobility was associated with changing the average molecular orientation in the glass .…”

Section: Introductionmentioning

confidence: 99%

High-Throughput Ellipsometric Characterization of Vapor-Deposited Indomethacin Glasses

2013

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A method for the high-throughput preparation and characterization of vapor-deposited organic glasses is presented. Depositing directly onto a substrate with a large temperature gradient allows many different glasses to be prepared simultaneously. Ellipsometry is used to characterize these glasses, allowing the determination of density, birefringence, and kinetic stability as a function of substrate temperature. For indomethacin, a model glass former, materials up to 1.4% more dense than the liquid-cooled glass can be formed with a continuously tunable range of molecular orientations as determined by the birefringence. By comparing measurements of many properties, we observe three phenomenological temperature regimes. For substrate temperatures from Tg + 11 K to Tg - 8 K, equilibrium states are produced. Between Tg - 8 K and Tg - 31 K, the vapor-deposited materials have the macroscopic properties expected for the equilibrium supercooled liquid while showing local structural anisotropy. At lower substrate temperatures, the properties of the vapor-deposited glasses are strongly influenced by kinetic factors. Different macroscopic properties are no longer correlated with each other in this regime, allowing unusual combinations of properties.

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Characterization of amorphous organic thin films, determination of precise model for spectroscopic ellipsometry measurements

Cited by 9 publications

References 15 publications

Investigation on optical and photoluminescence properties of organic semiconductor Al-Alq3 thin films for organic light-emitting diodes application

Investigation on optical and photoluminescence properties of organic semiconductor Al-Alq3 thin films for organic light-emitting diodes application

A Comparison Study of the Organic Small Molecular Thin Films Prepared by Solution Process and Vacuum Deposition: Roughness, Hydrophilicity, Absorption, Photoluminescence, Density, Mobility, and Electroluminescence

High-Throughput Ellipsometric Characterization of Vapor-Deposited Indomethacin Glasses

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