Accelerated pre-oxidation method for healing progressive electrical short in organic light-emitting devices

Kim, Youngkyoo; Choi, Dongkwon; Lim, Hyun Sook; Ha, Chang‐Sik

doi:10.1063/1.1564872

Cited by 40 publications

(45 citation statements)

References 17 publications

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“…Residual products from the polymer synthesis/deposition, chemical reactions among device elements as well as the presence of oxygen and water may promote internal device degradation, which is observed even when hermetic encapsulation is used. [11] Devices based on two other conjugated polymers, ITO/ PPV/Al [PPV: poly(p-phenylene vinylene)] and ITO/ PDOFV/Ca [PDOFV: poly(9,9 0 -dioctyl-2,7-fluorenylene vinylene], were also tested, presenting results which are qualitatively similar to those based on POT. …”

Section: Resultssupporting

confidence: 54%

Simple and Fast Organic Device Encapsulation Using Polyisobutene

Toniolo

Hümmelgen

2004

Macro Materials & Eng

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Summary: We demonstrate the use of polyisobutene (PIB) in a glass encapsulation method suitable for organic devices. The PIB viscosity at environmental temperatures provides a fast and non‐aggressive passivant layer formation method for device protection with glass. Due to its fully aliphatic character, PIB is suitable for passivating organic light‐emitting and photovoltaic devices. The observed preservation of encapsulated Ca films demonstrates the PIB suitability for air‐unstable metals passivation. Stable I(V) characteristics and increased operational lifetime were observed in PIB‐encapsulated organic devices. This encapsulation method is cheap, simple, and dispenses intensive equipment use, so that it is appropriate even for laboratories with restricted experimental facilities.

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Section: Resultssupporting

confidence: 54%

Simple and Fast Organic Device Encapsulation Using Polyisobutene

Toniolo

Hümmelgen

2004

Macro Materials & Eng

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“…In case of OLED displays made using small molecules, it has been reported that a progressive electrical short (PES) phenomenon is responsible for the degradation of display pixels during long time operation [8]. This report claimed that the PES phenomenon is closely related to the formation of unstable defects in organic layers which eventually leads to catastrophic degradation of whole layers in pixels.…”

Section: Introductionmentioning

confidence: 88%

“…Next, a 20 nm thick hole-transporting layer (HTL), N,, was deposited at 0.1 nm/s. Onto the HTL an emission layer (EML), which is a mix of tris(8-hydroxyquinolinato) aluminum (Alq 3 ) and 9-benzothiazol-2-yl-1,1,6,6-tetramethyl-2,3,5,6,7a,11a-hexahydro-1H,4H-11-oxa-3a-aza-benzo [de]anthracen-10-one (C545T), was deposited as reported previously [8]. Then additional Alq3 layer (20 nm thick) as an electron-transporting layer (ETL) was deposited on top of the EML, followed by depositing LiF (0.7 nm, 0.01 nm/s) as an electron-injecting layer (EIL) and Al cathode (120 nm, 0.5 nm/s) through a shadow mask (open width = 200 μm; open length = 44 mm).…”

mentioning

confidence: 99%

“…The resulting OLED displays feature 128 128 pixels and 1.7 inch (diagonal) active image area. Finally these OLED displays fabricated were encapsulated with a conventional stainless steel canister attaching a desiccant film [4,8].Current-voltage (I-V) characteristics of OLED displays were measured using a specialized jig system, equipped with an electrometer (Keithley 238) and a multichannel scanner, which was designed to probe the current of each pixel. The average luminance of the present PM-OLED displays was measured using a candela meter (PR 650).…”

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confidence: 99%

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Melting Effect of Hole-Injecting Layer on the Performance of Passive Matrix Organic Light-Emitting Displays

Kim¹,

Choi²,

Kim³

2008

TOPCJ

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Abstract:Here we report improved operation stability of passive matrix organic light-emitting displays (PM-OLED) by melting a hole-injecting layer (HIL) that is the first organic layer contacting anode. The PM-OLED displays fabricated in this work are consisted of 128 128 pixels in which each pixel has a dimension of 200μm 200μm. The exact thermal transition behaviour of hole-injecting material was first examined using a differential scanning calorimeter in order to decide the melting temperature for the HIL melting process (300 o C/3min). Results show that the display with the untreated (ascoated) HIL exhibited large leakage current which eventually resulted in damages (black cross-talk lines) to the display during operation. However, no cross-talk defect was observed for the PM-OLED display with the thermally treated (melted) HIL, which was supported by the absence of leakage current at reverse bias.Since the breakthrough works on organic light-emitting devices (OLED) based on either low-molecular-weight materials (i.e., small molecules) [1] or polymers [2], OLED displays are now in market even though their applications are limited to small size display for MP3 players, mobile phones, car front panel devices, shavers, etc [3,4]. This successful debut of OLED display into market can be mainly attributed to remarkable advances in organic semiconductor materials and process technology [3][4][5].However, these OLED displays do still suffer from their short lifetime though the thermal stability of organic materials themselves has been significantly improved when it comes to the test device measurement [4,6,7]. In case of OLED displays made using small molecules, it has been reported that a progressive electrical short (PES) phenomenon is responsible for the degradation of display pixels during long time operation [8]. This report claimed that the PES phenomenon is closely related to the formation of unstable defects in organic layers which eventually leads to catastrophic degradation of whole layers in pixels. In this report the PES phenomenon could be healed by thermal treatment at temperatures below 100 o C in the presence of oxygen. This indicates that the defects become just oxidized in the presence of minimal molecular (translational) movement by thermodynamic effects, which means that the fundamental defects such as voids in either among molecules or between layers cannot be completely recovered.In this work we have attempted to cure these defects by melting organic layers, particularly focusing on a holeinjecting layer (HIL) that is the first layer contacting the anode of passive matrix (PM) OLED display (see the crosssectional device structure in Fig. 1a). The process time of HIL melting was controlled as short as possible in order to *Address correspondence to this author at the Department of Chemical Engineering, Kyungpook National University, Republic of Korea; avoid a large scale deformation of the HIL layer geometry, whilst the melting process temperature chosen was above the intrinsic melting point o...

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“…4 However, the commercialization of OLED is still awkward and very limited to a small size display because the device reliability (lifetime) lags behind the criteria of consumer electronics, even though it has been improved by device engineering such as accelerated pre-oxidation method (APOM). 5 This teaches us a concrete lesson that enhancing device reliability depends critically on the intrinsic property of organic semiconductor materials which includes chemical, physical, and thermal stabilities. In this regard, we have extensively studied thermally stable polymers and hybrid composite systems.…”

Section: Introductionmentioning

confidence: 99%