Studies on influence of light on fluorescence of Tris-(8-hydroxyquinoline)aluminum thin films

Thangaraju, K.; Amaladass, P.; Bharathi, K. Shanmuga; Mohanakrishnan, Arasambattu K.; Narayanan, V.; Kumar, J.

doi:10.1016/j.apsusc.2008.12.079

Cited by 25 publications

(19 citation statements)

References 12 publications

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“…For the light exposed Alq 3 sample in the cyclic-voltammetric measurement, a reversible behaviour is observed with the oxidation potential around 0.7805 V and reduction potential around À0.9492 V as shown in Figure 2. It has been reported that among the three 8-hydroxyquinoline (HQ) units in Alq 3 molecule, one HQ unit is affected (structural and chemical modifications) during the light exposure in the normal ambient and explained that the affected resultant Alq 3 molecule containing carbonyl group acts as fluorescent quencher, quenching the fluorescence of Alq 3 thin film [17,18,20,21] . The reduction potential (À2.0148 V) of as prepared Alq 3 sample is found to be decreased with the appearance of oxidation potential at 0.7805 V during the light exposure under the normal ambient.…”

Section: Results and Discussion Cyclic Voltammetric Studiesmentioning

confidence: 99%

“…It confirms the quenching of fluorescence of as-prepared Alq 3 thin films during the light exposure in the normal ambient. It has been reported that the affected resultant Alq 3 molecule during the light exposure in the normal ambient containing carbonyl group acts as fluorescent quencher and number of luminescent quencher in the light exposed Alq 3 sample is not substantial but limited to a few [17,18,20,21] . It is reported that the energy of excitons in the Alq 3 molecule in the light exposed Alq 3 thin films can be non-radiatively transferred to its neighbouring luminescent quencher, quenching 3D contour emission of light exposed Alq 3 thin films in the normal ambient.…”

Section: D Contour Emission Studiesmentioning

confidence: 99%

“…Aziz et al [11] reported that the fluorescence efficiency of Alq 3 thin film in the device is decreasing during the operation and explained that the cationic Alq 3 species are unstable and their degradation product acts as luminescent quencher. It has been reported that among the three 8-hydroxyquinoline (HQ) units in Alq 3 molecule, one HQ unit is affected (structural modifications) during the light exposure in the normal ambient and explained that the affected resultant Alq 3 molecule containing carbonyl group acts as fluorescent quencher, quenching the fluorescence of Alq 3 thin film [17,18] .…”

Section: Introductionmentioning

confidence: 99%

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Studies on the Fluorescence of Tris-(8-hydroxyquinoline)Aluminum and the Effect of Light Exposure

Thangaraju

Amaladass

Mohanakrishnan

et al. 2010

Polymer-Plastics Technology and Engineering

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Organic Tris-(8-hydroxyquinoline)aluminum (Alq 3 ) thin films, one of the most widely used electron transport as well as emissive materials in the organic electroluminescent (EL) devices, have been deposited on glass substrates by thermal evaporation process. The deposited Alq 3 thin films were exposed to light in the normal ambient. The effect of light exposure on the fluorescence of Alq 3 sample and formation of luminescent quencher has been studied using cyclic voltammeter and 3D contour emission spectroscopy. It is observed that the luminescent quencher can be formed in the Alq 3 during the light exposure, quenching the emission of light exposed sample. It is found that the energy of excitons in the Alq 3 molecule in the light exposed Alq 3 thin films can be non-radiatively transferred to its neighbouring luminescent quencher, quenching the emission of light exposed Alq 3 thin films.

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Section: Results and Discussion Cyclic Voltammetric Studiesmentioning

confidence: 99%

Section: D Contour Emission Studiesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Studies on the Fluorescence of Tris-(8-hydroxyquinoline)Aluminum and the Effect of Light Exposure

Thangaraju

Amaladass

Mohanakrishnan

et al. 2010

Polymer-Plastics Technology and Engineering

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“…However, the highly-efficient tandem OLEDs have yet to be obtained when using such CGLs because of the delicate problems that are encountered at high deposition temperatures. Even though studies concerning the fabrication and the characterization of the tandem OLEDs with an inserted layer containing zinc phthalocyanine (ZnPc) and fullerene (C60), which has an advantage of a low deposition temperature, have been suggested, the efficiency enhancement mechanisms of the corresponding OLEDs have not yet been clearly clarified due to the poor transmittances of the ZnPc and the C60 materials [19].…”

Section: Introductionmentioning

confidence: 99%

Efficiency enhancement in tandem organic light-emitting devices with a hybrid charge generation layer composed of BEDT-TTF-doped TPBi/mCP/HAT-CN

Kim

2014

Organic Electronics

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“…Kumar et al 11 employed ellipsometry, photoluminescence and infrared spectroscopies to study the influence of light exposure on the optical properties of Alq 3 films. Attenuation of the photoluminescence of Alq 3 films exposed to light is discussed by Thangaraju et al 12 using fluorescence, FT-IR, mass, MALDI-ToF-MS and 1 H and 13 C NMR spectroscopy. They reported that the affected molecule contains the carbonyl group, which acts as fluorescence quencher.…”

Section: Introductionmentioning

confidence: 99%

Spectroscopic evidence of photodegradation by ultraviolet exposure of tris(8-hydroxyquinoline) aluminum (Alq3) thin films

Brito¹,

Aráujo²,

Quirino³

et al. 2010

J. Braz. Chem. Soc.

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A degradação extrínseca de diodos orgânicos emissores de luz (OLEDs) permanece como uma questão crucial, especialmente no que se refere à degradação, devido à exposição à luz. Poucos estudos existem e faltam dados a respeito dos produtos de fotodegradação e respectivos mecanismos, responsáveis pela extinção da luminescência. Com o objetivo de investigar os mecanismos de degradação causados pela exposição à luz de filmes finos de Alq 3 usado com sucesso como camada transportadora de elétrons e material emissivo na fabricação de OLEDs, a fotodegradação foi monitorada em função da irradiação com luz UV através das técnicas de fotoabsorção e de fotoemissão nas bordas 1s do carbono, do nitrogênio e do oxigênio bem como nas bordas 2s e 2p do alumínio. A influência da exposição à luz foi simulada com o emprego de três comprimentos de onda diferentes: 254, 365 e 307 nm, os dois primeiros correspondendo aproximadamente a máximos de absorção no espectro de UV do Alq 3 . Após exposição, todos os espectros apresentam um decréscimo nos sinais de fotoabsorção e de fotoemissão. Entretanto, enquanto a radiação de 307 nm causa mudanças menores nos espectros de NEXAFS, modificações mais acentuadas são observadas para a exposição a 254 e 365 nm. Medidas de fotoemissão para filmes finos de Alq 3 não-irradiado e irradiado com luz de 307 nm também foram conduzidas. Embora o sinal correspondente ao alumínio mantém-se praticamente intacto, mudanças mais significativas são observadas nas intensidades e deslocamentos dos picos nas bordas 1s do carbono, do nitrogênio e do oxigênio.The extrinsic degradation of organic light emitting diodes (OLEDs) remains a critical issue especially concerning degradation due to exposure to light. Very few studies exist and little is known about the related photodegradation products and mechanisms, responsible for quenching of luminescence. In order to gain insight into the degradation mechanisms caused by light exposure of Alq 3 thin films, used successfully as electron transport layer and emissive material in the fabrication of OLEDs, we have monitored UV photodegradation through synchrotron radiationbased photoabsorption and photoemission techniques at the carbon, nitrogen, and oxygen 1s edges as well as at the aluminum 2s and 2p edges. The influence of light exposure was simulated using three different wavelengths, namely 254, 365 and 307 nm, the first two nearly corresponding to absorption maxima in the UV spectrum of Alq 3 . After exposure all spectra show decrease of the photoabsorption and photoemission signals. However, while irradiation at 307 nm causes lesser changes in the total electron yield NEXAFS spectra, strong spectral modifications are observed for 254 and 365 nm exposures. Core level photoemission measurements from non-irradiated and irradiated Alq 3 thin films at 307 nm were also performed. While the Al peaks maintained almost intact, changes in peak intensities as well as shifts for carbon, nitrogen and oxygen are much more dramatic.Keywords: OLED degradation, tris(8-hydroxyquinoline)...

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Studies on influence of light on fluorescence of Tris-(8-hydroxyquinoline)aluminum thin films

Cited by 25 publications

References 12 publications

Studies on the Fluorescence of Tris-(8-hydroxyquinoline)Aluminum and the Effect of Light Exposure

Studies on the Fluorescence of Tris-(8-hydroxyquinoline)Aluminum and the Effect of Light Exposure

Efficiency enhancement in tandem organic light-emitting devices with a hybrid charge generation layer composed of BEDT-TTF-doped TPBi/mCP/HAT-CN

Spectroscopic evidence of photodegradation by ultraviolet exposure of tris(8-hydroxyquinoline) aluminum (Alq3) thin films

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