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Author: search.filters.author.Chittawanij, Apisit

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    Improvement of power efficiency of hybrid white OLEDS based on p-i-n structures
    (2018-01-01)
    Chittawanij, Apisit
    ;
    Locharoenrat, Kitsakorn
    In this article, hybrid white organic light-emitting diodes (WOLEDs) under p-i-n structures have been investigated in terms of power efficiency. By using tris(8-hydroxy quinolinato) aluminum (Alq<inf>3</inf>) doped with 8-hydroxy-quinolinato lithium (Liq) as an n-type and WHI112 doped with molybdenum trioxide (MoO<inf>3</inf>) as a p-type, the typical device structure of ITO/WHI112: 20 wt.% MoO<inf>3</inf> (55 nm)/HTG-1 (10 nm)/UBH15: 3 wt.% EB502 (10 nm)/EPH31: 3 wt.% EPY01 (25nm)/3TPYMB (10 nm)/Alq<inf>3</inf>: 33 wt.% Liq (25 nm)/Al (150 nm) was fabricated. It has been found that the p-i-n device based device showed the lowest driving voltage and highest power efficiency among the undoped and n-type devices. At the current density of 20 mA/cm<sup>2</sup>, the roll-off of the efficiency in the p-i-n device was much smaller than the n-type and the undoped devices. The current and power efficiency of the p-i-n device were maintained with 17.2 cd/A and 5.1 lm/W at 100 mA/cm<sup>2</sup>, it was reduced to 7.5 % and 21 %, respectively. In contrast, the n-type device exhibited the significant reduction of efficiency (14.4 cd/A and 3.8 lm/W at 80 mA/cm<sup>2</sup>), it was reduced to 20 % and 39.6 %, respectively. The superior performances of the p-i-n structure based device were attributed to the high hole injection ability of WHI112:MoO<inf>3</inf> and high electron mobility of Alq<inf>3</inf>:Liq, leading to high power efficiency and low driving voltage. A better balance of electrons and holes could contribute to a good current efficiency for the device. These findings strongly indicated that carrier injection ability and balance showed significant affects on the performance of OLED.
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    Characteristic Evaluation of Organic Light-Emitting Diodes Prepared with Stamp Printing Technique
    (2017-01-01)
    Chittawanij, Apisit
    ;
    Locharoenrat, Kitsakorn
    We have reported on a stamp printing technique that uses PET release film as a printing stamp to deposit TPBi thin film served as the electron transport layer of the organic light-emitting diodes. TPBi thin film was printed with a good uniformity and resolution. Effect of deposition conditions on optical and electrical properties and surface roughness of TPBi thin film have been studied under spectroscopy and atomic force microscopy, respectively. It is found that characteristic of TPBi thin film is improved via controlled stamp temperature and time. Since TPBi thin film exhibits the surface morphology comparable to that of conventional spin-coating thin film, our findings suggest that PET release film-based stamp printing approach is possible to use as an alternative deposition of the organic thin film as compared with a traditional one.
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    Material structure selection of blue organic light emitting diodes utilizing a hybrid experimental design
    (2016-08-12)
    Shie, Jie Ren
    ;
    Chittawanij, Apisit
    ;
    Hong, Lin Ann
    ;
    Lai, Chang Jun
    ;
    Lai, Yun Jr
    A hybrid approach integrating a Taguchi orthogonal table with an irregular design of experiments (DOE) method was proposed for selecting an optimal material structure of blue organic light emitting diodes in order to achieve multi-objective quality characteristics of devices. Analysis of variance (ANOVA) was adopted to identify significant factors before regression models were obtained. Finally, an optimal material structure was determined by maximizing a desirability function relating to selected critical quality characteristics including the driving voltage, the luminance, and luminance efficiency.