The Effect of Annealing of Organic Thin Films on Charge Injection in Organic Electroluminescent Devices.

Ishihara, Masahiko; Okumoto, Kenji; Shirota, Yasuhiko

doi:10.2494/photopolymer.15.769

Cited by 2 publications

(2 citation statements)

References 12 publications

(13 reference statements)

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“…It has been earlier reported that with annealing, the electron only device alone showed improved performance. 12 However, since the m-MTDATA device also exhibited overall lowering of current, further examination is necessary.…”

Section: Single Layer Devicesmentioning

confidence: 99%

“…With annealing, the electron only devices showed improvement and the hole only device showed no improvement. 12 Selective thermal heating has been useful to improve the properties, especially annealing the Al layer, which indicated that the electron injection was otherwise poor. 13 Annealing at 70 1C for 5 hours helped improving the performance of a Alq 3 based OLED.…”

Section: Introductionmentioning

confidence: 99%

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Effect of the electric field during annealing of organic light emitting diodes for improving its on/off ratio

Sharma

Katiyar

Rao

et al. 2016

Phys. Chem. Chem. Phys.

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If an organic light emitting diode is to be used as part of a matrix addressed array, it should exhibit low reverse leakage current. In this paper we present a method to improve the on/off ratio of such a diode by simultaneous application of heat and electric field post device fabrication. A green OLED with excellent current efficiency was seen to be suffering from a poor on/off ratio of 10(2). After examining several combinations of annealing along with the application of a reverse bias voltage, the on/off ratio of the same device could be increased by three orders of magnitude, specifically when the device was annealed at 80 °C under reverse bias (-15 V) followed by slow cooling also under the same bias. Simultaneously, the forward characteristics of the device were relatively unaffected. The reverse leakage in the OLED is mainly due to the injection of minority carriers in the hole transport layer (HTL) and the electron transport layer (ETL), in this case, of holes in tris-(8-hydroxyquinoline)aluminum(Alq3) and electrons in 4,4',4''-tris(N-3-methylphenyl-N-phenylamino)triphenylamine (m-MTDATA). Hence, to investigate these layers adjacent to the electrodes, we fabricated their single layer devices. The possibility of bulk traps present adjacent to electrodes providing states for injection was ruled out after estimating the trap density both before and after the reverse biased annealing. The temperature independent current in reverse bias ruled out the possibility of thermionic injection. The origin of the reverse bias current is attributed to the availability of interfacial hole levels in Alq3 at the cathode work function level in the as-fabricated device; the suppression of the same being attributed to the fact that these levels in Alq3 are partly removed after annealing under an electric field.

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Section: Single Layer Devicesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effect of the electric field during annealing of organic light emitting diodes for improving its on/off ratio

Sharma

Katiyar

Rao

et al. 2016

Phys. Chem. Chem. Phys.

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Metal-Free Oxidative C–C Coupling of Arylamines Using a Quinone-Based Organic Oxidant

2017

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A variety of arylamines are shown to undergo oxidative C-C bond formation using quinone-based chloranil/H reagent as the recyclable organic (metal-free) oxidant system to afford benzidines/naphthidines. Arylamines (3°/2°) designed with various substituents were employed to understand the steric as well as electronic preferences of oxidative dimerization, and a mechanism involving amine radical cation has been proposed. The tetraphenylbenzidine derivative obtained via oxidative C-C coupling has been further converted to blue-emissive hole-transporting material via a simple chemical transformation. This study highlights the preparation of novel HTMs in a simple, economic, and efficient manner.

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The Effect of Annealing of Organic Thin Films on Charge Injection in Organic Electroluminescent Devices.

Cited by 2 publications

References 12 publications

Effect of the electric field during annealing of organic light emitting diodes for improving its on/off ratio

Effect of the electric field during annealing of organic light emitting diodes for improving its on/off ratio

Metal-Free Oxidative C–C Coupling of Arylamines Using a Quinone-Based Organic Oxidant

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