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[2015 OLED Evaluation Seminar] Oxide TFT Technology that 2015 should Spotlight

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By Hyun Jun Jang

 

During the 2015 OLED Evaluation Seminar (December 4) hosted by UBI Research, Professor Jin-Seong Park of Hanyang University gave a presentation titled OLED Oxide TFT Technology Trend, discussing oxide TFT, related industry, and technological issues as well as TFT technology that should receive the spotlight in 2016.

 

Oxide TFT has an advantage of high mobility and large area uniformity compared to a-Si TFT. As such, it is being more applied to large area OLED panel and used in LG Display’s OLED TV.

 

Park revealed that there are mainly 4 issues regarding oxide TFT and led with the reliability issue. Oxide TFT is essentially in amorphous state but when crystalized, the density and crystallizability increase; as oxygen does not move away and stay in place, defects occur less and reliability is high. Japan’s SEL and Sharp published CAAC (C-Axis Aligned Crystal) structure related oxide TFT paper, and Cornell University produced CAAC oxide TFT by increasing the substrate temperature and adjusting oxygen’s partial pressure.

 

The second issue is composition ratio. Park reported that composition ratio is the most closely related characteristic to TFT’s mobility. He revealed that recently research is being carried out centering around IGZO (indium gallium zinc oxide), but also oxide TFT research with different composition ratio is continually published. For example, ITZO (indium tin zinc oxide)’s mobility has been reported to reach 30cm/Vsec, and BOE is working on the related research. Research results, which showed increased mobility and reliability for IGZTO, which is IZTO with G added, was published, as well as ZnON (zinc oxide nitride) TFT’s 100cm/Vsec mobility. BOE demonstrated ZnO TFT applied 14.1inch AMOLED.

 

The third issue is the device structure. Park explained that efficiency can increase when top gate structure is used to oxide TFT as parasitic capacitor is not needed, but that the process is difficult. However, Park reported that JOLED revealed when self-alignment is used the number of masks used can be reduced and increases performance. This structure is applied to OLED TV by LG Display.

 

Lastly, Park gave the safety of device as the last issue. Oxide TFT can exhibit degradation effects from light, oxygen, hydrogen, and moisture. Park reported that hydrogen particularly has great effect on the safety. He explained that although the current prevailing OLED TFT is LTPS, as the panel becomes larger there will be technological competition between oxide and LTPS. Reporting that TFT which is cost efficient and shows high performance in diverse factors such as resolution will dominate the market, Park concluded his presentation.

 

 

 

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[SID 2015] OLED’s Endless Evolution. SEL Reveals 8K Foldable AMOLED Panel

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During the author interview on 3 June, first day of SID 2015 Symposium, Japan’s SEL (Semiconductor Energy Laboratory) revealed 13.5 inch 8K foldable AMOLED panel and drew most attention in the room. During the last year’s SID, SEL showcased OLED’s most evolved product at the time with 5.9 inch foldable AMOLED panel and 13.3 inch 8K AMOLED panel.

The 13.5 inch 8K foldable AMOLED panel that was shown this year is a product that combined last year’s foldable and 8K technology. It utilized RGB laminated white OLED, RGB color filter, and top emission structure. Additionally, 664ppi was actualized through 3Tr+1C/Cell structure and external correction method.

[SID 2015] High Resolution OLED for Commercial Display Too! SEL Reveals 81inch Multi OLED Display

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Commercial display is a display installed in public areas. With the advantage of being able to deliver various information without being restricted to a place or time, it is becoming a new display market.

 

In order to lead increasingly expanding commercial display market, key panel companies are leaning toward high resolution and large size panel exhibitions. Recently released commercial displays have enlarged the size by attaching small LCD panels in a tile style creating bezel between panels. In LCD sector, commercial display products with minimized bezel are being developed.

 

However, 8K ultra high resolution commercial display has been produced without bezel through OLED. In SID 2015, SEL revealed world’s largest 81inch 8K OLED multi display that was produced by combining 36 13.5inch 8K flexible AMOLED panels.

 

The key technology is transparent sections of right and bottom edges of the panel. The FPC and scan driver sections of each panel are overlapped with corners of transparent edges (see below diagram).

 

SID 2015 커머셜 디스플레이3

 

 

Daiki Nakamura of SEL revealed that commercial displays of various sizes and shapes can be produced using flexible AMOLED panel and as it is suitable for applications on columns, commercial display can be a new market for OLED.

 

SEL had previously exhibited 27inch 8K multi OLED display using 4 13.5 inch 8K flexible OLED panels in Display Innovation 2014.

 

SEL’s 81inch 8K Multi OLED Display, SID 2015

SEL’s 81inch 8K Multi OLED Display, SID 2015

 

[SID 2015] OLED’s Endless Evolution. SEL Reveals 8K Foldable AMOLED Panel

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During the author interview on 3 June, first day of SID 2015 Symposium, Japan’s SEL (Semiconductor Energy Laboratory) revealed 13.5 inch 8K foldable AMOLED panel and drew most attention in the room. During the last year’s SID, SEL showcased OLED’s most evolved product at the time with 5.9 inch foldable AMOLED panel and 13.3 inch 8K AMOLED panel.

The 13.5 inch 8K foldable AMOLED panel that was shown this year is a product that combined last year’s foldable and 8K technology. It utilized RGB laminated white OLED, RGB color filter, and top emission structure. Additionally, 664ppi was actualized through 3Tr+1C/Cell structure and external correction method.

SEL2 SEL1

Finding a way for OLED industry in flexible

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Samsung is preparing to introduce foldable AMOLED panel applied mobile product, and LG will release a new product with the flexible AMOLED panel in the latter half of this year.

As the flexible OLED commercializes, its R&D also accelerates. It was analyzed that the trend of papers published at SID 2014 is the flexible OLED as 9 more papers totaling 23 regarding the flexible OLED were published at SID 2014 than 14 papers 2013.

SEL displayed its best technology in the flexible OLED by introducing a tri-folded AMOLED panel, a book type AMOLED panel, and 13.5” and 5.2” high resolution flexible AMOLED panels at SID 2014. AMOLED latecomers such as AUO, BOE and CSOT also published papers on the flexible AMOLED panel and showed that more display companies are entering the flexible OLED development.

As such, active R&D on the flexible OLED is carried out by industry-academic-institute, and it is expected that the flexible will be more focused in the OLED display sector. A keyword of the flexible will differentiate it from the LCD and is expected to lead the display industry.

140625_ SEL’s 5.9” tri-folded AMOLED panel at SID2014

 SEL’s 5.9” tri-folded AMOLED panel at SID2014