Performance enhancement of organic light-emitting diode by heat treatment

Wong, Fu-Lung; Sun, Haiyan; Tong, S. W.; Chan, Mei‐Yee; Lee, C.S.; Lee, S.T.

doi:10.1016/j.jcrysgro.2005.12.032

Cited by 6 publications

(8 citation statements)

References 19 publications

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“…In particular, recent thermal treatments have shown both sizeable spectral and intensity variations of PL in Alq 3 films [2][3][4][5][6][8][9][10][11][12], and it has also been found that post annealing treatments contribute to better efficiency and lifetime enhancement of OLEDs containing Alq 3 [13][14][15][16][17][18]. However, the above studies are far from being systematic, and hardly clarify the properties of Alq 3 thin films, as far as the consequences of thermal treatments on PL and aggregation processes are concerned.…”

Section: Introductionmentioning

confidence: 99%

Morphological phase transitions in films

Baldacchini

Chiacchiaretta

et al. 2009

Journal of Luminescence

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Section: Introductionmentioning

confidence: 99%

Morphological phase transitions in films

Baldacchini

Chiacchiaretta

et al. 2009

Journal of Luminescence

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“…As seen in Fig 1.25, after 1200mins of ambient exposure, almost 40% of the emissive area of the untreated device became non-emissive [52]. On the other hand, the dark-spot in the 7.5 and 15-min heated devices were still small in diameter (most less than 0.08 mm) [52]. The 7.5-min heated device gave the slowest dark spot growth.…”

Section: Effect Of Elevatedmentioning

confidence: 91%

“…Investigations into the effects of annealing(i.e. post-deposition heating) on OLED operation conducted by several other groups also show positive results [51][52]. Chen et al [51] showed that by annealing OLEDs (ITO/NPB/ Alq 3 /Mg:Ag/Ag) at 100°C which is much below the T g of NPB, high current density and lower driving voltages could be achieved.…”

Section: Effect Of Elevatedmentioning

confidence: 94%

“…Another study by Wong et al [52] showed the advantageous effect of annealing the entire device, i.e. after deposition, at 70°C for 7.5mins.…”

Section: Testing Methodsmentioning

confidence: 99%

“…Hence it can be concluded that depositing the cathode at 65°C substrate temperature leads to definite dark spot suppression. post deposition heating) of the entire OLED at 70°C for 7.5mins [52]. Since we have selected metal deposition temperature to be 65°C, the annealing temperature is also set at 65°C for the comparative investigation.…”

Section: Effect Of Elevated Temperature Cathode Deposition On Dark Spmentioning

confidence: 99%

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Dependence of dark spot growth on cathode/organic interfacial adhesion in organic light emitting devices

Phatak¹,

Tsui²,

Aziz³

2012

Journal of Applied Physics

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The growth of dark spots in organic light emitting devices (OLEDs) with cathodes deposited at 65°C instead of the conventional room temperature deposition, or which contain a metal-organic-mixed layer at the cathode contact, is investigated. The results reveal a strong correlation between the growth rate of dark spots and adhesion at the cathode-organic interface, where stronger adhesion results in a slower growth of dark spots. The findings shed light on the beneficial effect of increasing interfacial adhesion on improving the ambient stability of OLEDs. Measures for increasing cathode-organic adhesion can be expected to be particularly beneficial for flexible OLEDs where device protection from the ambient is more challenging.

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Synthesis and Characterization of Hemicage 8-Hydroxyquinoline Chelates with Enhanced Electrochemical and Photophysical Properties

2007

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A new hexadentate, tripodal 8-hydroxyquinoline ligand (QH3) and its trivalent metal chelates (MQ, M=Al3+, Ga3+, In3+) with hemicage structures have been prepared and the electrochemical and photophysical properties systematically studied. The hemicage structure of the metal complexes was characterized by 1H NMR, indicating a pure facial geometry, in contrast to their uncaged cousins with 8-hydroxyquinoline (Mq3) and 3-methyl-8-hydroxyquinoline (M(3Meq)3), which all exist only as the meridional form in fluid solutions at room temperature. The photoluminescence quantum efficiency for the three hemicage complexes is 1.48, 1.79, and 1.26 times higher for AlQ, GaQ, and InQ, respectively, than their corresponding 3-methyl-8-hydroxyquinoline complexes, likely due to the rigidity of the ligand system, which can efficiently decrease the nonradiative decay of the excited states. The improved electrochemical stability of the hemicage complexes has been demonstrated by cyclic voltammetry, showing an increasingly reversible behavior from InQ to GaQ to AlQ (Ered=-2.15, -2.17, and -2.22 V vs Fc/Fc+ in DMSO). We infer that the degree of reversibility and redox potential result from the metal-ligand bond strength, which is largest in the case of aluminum.

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Performance enhancement of organic light-emitting diode by heat treatment

Cited by 6 publications

References 19 publications

Morphological phase transitions in films

Morphological phase transitions in films

Dependence of dark spot growth on cathode/organic interfacial adhesion in organic light emitting devices

Synthesis and Characterization of Hemicage 8-Hydroxyquinoline Chelates with Enhanced Electrochemical and Photophysical Properties

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