Active Matrix Organic Light Emitting Diode (AMOLED) displays offer distinct benefits for portable electronics applications, including light weight, high brightness, low power consumption, wide viewing angle, and low processing costs. They are also attractive candidates for highly flexible substrates. Since then several research groups have demonstrated circuits and displays on flexible substrate using a-Si:H, oxide TFT and also organic/inorganic CMOS technologies. In ADRC, the oxide TFT based flexible backplanes is studied.

1) Flexible substrates
Polyimide (PI) can stand high processing temperatures is one preferable candidate plastic substrate for fabricating flexible electronics. During the devices fabrication, glass substrates are used as the cattier substrate, on which the PI imbedded with grapheme oxide (GO) and carbon nanotube (CNT) are coated. The flexible substrates are then realized after the detachment as shown in Figure 1.

Figure 1. Optical image of PI substrate after detachment

2) Flexible a-IGZO TFT
After the formation of the PI film on the carrier glass, the IGZO TFTs are subsequently on the substrate. The transfer and output characteristics are shown in figure 2.

 

Figure 2. The a-IGZO TFT performance on PI substrate

 

3) AMOLED Design
A 2-inch QVGA (320 × 240) bottom-emission AMOLED display with integrated gate driver utilizing conventional 2T + 1C pixel circuits is demonstrated in ADRC. Figure 3 shows the layout of array, unit pixel and the prototype yellow monochrome AMOLED display on PI substrate.

 

Figure 3. The layout of array, unit pixel and prototype yellow monochrome AMOLED display on PI substrate

 

 

4) Flexible AMOLED
ADRC we have OLED equipment to deposit HIL, HTL, EML, ETL and EIL together with LiF and Al for AMOLED manufacturing. OLED efficiency is over 100 cd/A for green and R,G,B can be deposited in the same chamber. We also have bonding equipment for driving circuits such as TAB and COG. 40 um pixel can be built on the glass or on PI/glass.

Related invited/plenary talks by Prof Jin Jang

1) “OLED backplane technology and flexible display”, Fan-Asia Technology Forum (2012.05.30-06.01, Island Shangri-La, Hong Kong)
2) “Technologies for flexible AMOLED”, FPD International China 2012 (2012.09.17-19, Beijing, China)
3) “TFT backplane technologies for AMOLED”, Printed Electronics Asia 2012 (2012.10.02-03, Hilton Tokyo, Japan)
4) TFT technologies for AMOLED backplane”, ITC 2010 (2010.01.28-29, Himeji, Japan)
5) “Core technologies for flexible AMOLED“, L&D Korea 2010-International Seminar on Display Technology (2010.09.03, Daegu EXCO, Kroea)
6) “Current issues in display development and future prospect, The Optical Sciety of Korea Summer Meeting 2012 (2012.08.27-29, Keumho Resort, Jeju, Korea)
7) “Technology issues for flexible AMOLED”, FPD International 2012 (2012.11.02-03, Yokohama, Japan)