Morphological phase transitions in films

Baldacchini, G.; Baldacchini, Tommaso; Chiacchiaretta, Piero; Pode, Ramchandra; Wang, Q.-M.

doi:10.1016/j.jlumin.2009.01.035

Cited by 14 publications

(17 citation statements)

References 21 publications

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“…Films of Gaq 3 annealed in nitrogen gas show an enhanced absorption and emission with respect to the pristine film, and also a blue shift of the emission band has been observed [8]. These experimental results are similar in several aspects to our previous ones [5,6] and to other ones never fully published until now, so that it deemed necessary to proceed to a detailed and systematic description of the experiments performed in Alq 3 films, in order to perform a meaningful comparative study. Only in this way it will be possible to understand what is going on at level of molecular interactions and to attempt, if possible, an extension of the obtained results to many other organic compounds, having in mind both basic properties of optical active materials and applications in OLEDs.…”

Section: Introductionsupporting

confidence: 79%

“…Moreover, during annealing processes not only the emission is consistently increased, as shown here in Figs. 7 and 8, but also the lifetime of the emission attains much longer values [5,6,15], which is another important factor for applications.…”

Section: Discussionmentioning

confidence: 99%

“…As a matter of facts, it was found that Alq 3 films display a sizeable variation of the intensity, peak wavelength, and linewidth of the emission band as a function of temperature up to 200 °C [5,6]. The particular behavior of such results suggested that they may have been originated by phase transition phenomena, which at their completion improved consistently the optical and morphological properties of the material, increasing so the general interest in Alq 3 as a crucial component of organic light emitting devices (OLEDs).…”

Section: Introductionmentioning

confidence: 99%

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Phase transitions in thermally annealed films of Alq3

Baldacchini¹,

Chiacchiaretta

Pode

et al. 2012

Low Temperature Physics

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Organic light emitting devices have been so very much improved lately that they are being widely applied for displays and lighting. Among many improving technologies, annealing processes in different atmospheres affect greatly their performance, for instance when the active material is the small molecule Alq 3 . In particular, a significant increase of the photoluminescence is observed in thin films of this molecule between 150 and 180 °C, before the physical destruction of the films occurs at higher temperatures. This phenomenon is attributed to a phase transition towards a novel morphological aggregation of the molecules in the film, which proved to be a much improved optical material for luminescent applications, and which seems common to other molecules as well.

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Section: Introductionsupporting

confidence: 79%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Phase transitions in thermally annealed films of Alq3

Baldacchini¹,

Chiacchiaretta

Pode

et al. 2012

Low Temperature Physics

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“…Experimental details about evaporation and annealing procedures, and optical absorption and emission measurements of films of Alq 3 have been described elsewhere (25,26). The twelve samples studied display an increase of the greenish emission wide band upon annealing, accompanied by a blue shift.…”

Section: Experimental and Resultsmentioning

confidence: 99%

“…Moreover, by looking more carefully at the results of Figures 1 and 5, it is easily observed that above 400 K (130 °C) the films are undergoing a phase transition (26,28). Indeed, the experimental data of Figure 1 are fitted with excitation energy processes, typical of phase transitions.…”

Section: Discussionmentioning

confidence: 99%

Why Annealing Processes Affect the Optical Properties of Alq3 Films and OLEDs

Baldacchini¹,

Baldacchini

Chiacchiaretta³

et al. 2009

ECS Trans.

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Organic light emitting diodes, OLEDs, have been so much improved in the last two decades that they are being currently used in commercial applications for displays and lighting. Among many improving technologies, thermal treatments affect greatly their performances. In case the small molecule Alq3 is the active material, it was never understood why and how the temperature could have played such an important role. Now, we have discovered that such molecules tend to aggregate themselves in morphological states which are very much sensible to annealing processes, with the result of improved emission efficiency and lifetime of Alq3 thin films. Moreover, the latter ones are described by a four components model, FCM, which has been validated by degradation experiments during 6 years, a world record in its own.

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Effect of thermal annealing on the structural and optical properties of tris‐(8‐hydroxyquinoline)aluminum(III) (Alq₃) films

Cuba

Muralidharan

2014

Luminescence

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Tris-(8-hydroxyquionoline)aluminum (Alq3 ) was synthesized and coated on to a glass substrate using the dip coating method. The structural and optical properties of the Alq3 film after thermal annealing from 50°C to 300°C in 50° steps was studied. The films have been prepared with 2 to 16 layers (42-324 nm). The thickness and thermal annealing of Alq3 films were optimized for maximum luminescence yield. The Fourier transform infrared spectrum confirms the formation of quinoline with absorption in the region 700 - 500/cm. Partial sublimation and decomposition of quinoline ion was observed with the Alq3 films annealed at 300°C. The X-ray diffraction pattern of the Alq3 film annealed at 50°C to 150°C reveals the amorphous nature of the films. The Alq3 film annealed above 150°C were crystalline nature. Film annealed at 150°C exhibits a photoluminescence intensity maximum at 512 nm when excited at 390 nm. The Alq3 thin film deposited with 10 layers (220 nm) at 150°C exhibited maximum luminescence yield.

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Morphological phase transitions in films

Cited by 14 publications

References 21 publications

Phase transitions in thermally annealed films of Alq3

Phase transitions in thermally annealed films of Alq3

Why Annealing Processes Affect the Optical Properties of Alq3 Films and OLEDs

Effect of thermal annealing on the structural and optical properties of tris‐(8‐hydroxyquinoline)aluminum(III) (Alq₃) films

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Morphological phase transitions in films

Cited by 14 publications

References 21 publications

Phase transitions in thermally annealed films of Alq3

Phase transitions in thermally annealed films of Alq3

Why Annealing Processes Affect the Optical Properties of Alq3 Films and OLEDs

Effect of thermal annealing on the structural and optical properties of tris‐(8‐hydroxyquinoline)aluminum(III) (Alq3) films

Contact Info

Product

Resources

About

Effect of thermal annealing on the structural and optical properties of tris‐(8‐hydroxyquinoline)aluminum(III) (Alq₃) films