Abstract:We have successfully reduced threshold voltage shifts of amorphous In–Ga–Zn–O thin‐film transistors (a‐IGZO TFTs) on transparent polyimide films against bias‐temperature stress below 100 mV, which is equivalent to those on glass substrates. This high reliability was achieved by dense IGZO thin films and annealing temperature below 300 °C. We have reduced bulk defects of IGZO thin films and interface defects between gate insulator and IGZO thin film by optimizing deposition conditions of IGZO thin films and ann… Show more
“…As shown in Figure 5(b), all devices emitted yellow light without defects even after being detached from a glass substrate. [14,15,16,17] After detachment process, we performed a bending test on the PLEDs device. In order to confirm that the PLED on the flexible CPI substrate has no significant degradation under bending test, we measured the performance of the device before and after bending test at the radius of 4 mm.…”
We have fabricated the flexible organic light-emitting diode (OLED) displays on 10 µm colorless polyimide (CPI) substrate using polymer light-emitting diode (PLED). The CPI was chosen as a substrate for flexible device because of its high transparency of around 90% at 550 nm and relatively high temperature process of >300 • C. All organic materials for OLED were deposited by spin coating technique and the OLED on PI substrate was encapsulated by the polyethylene terephthalate (PET) film with barrier layer. The PLEDs have a driving voltage of 3 V at 1000 cd/m 2 , and the current efficiency of 11.7 cd/A for the device on CPI substrate at 1000 cd/m 2 .
“…As shown in Figure 5(b), all devices emitted yellow light without defects even after being detached from a glass substrate. [14,15,16,17] After detachment process, we performed a bending test on the PLEDs device. In order to confirm that the PLED on the flexible CPI substrate has no significant degradation under bending test, we measured the performance of the device before and after bending test at the radius of 4 mm.…”
We have fabricated the flexible organic light-emitting diode (OLED) displays on 10 µm colorless polyimide (CPI) substrate using polymer light-emitting diode (PLED). The CPI was chosen as a substrate for flexible device because of its high transparency of around 90% at 550 nm and relatively high temperature process of >300 • C. All organic materials for OLED were deposited by spin coating technique and the OLED on PI substrate was encapsulated by the polyethylene terephthalate (PET) film with barrier layer. The PLEDs have a driving voltage of 3 V at 1000 cd/m 2 , and the current efficiency of 11.7 cd/A for the device on CPI substrate at 1000 cd/m 2 .
“…Therefore, polyimide was chosen as the base material to develop our flexible AMOLED. However, even for the high‐heat‐resistant polyimide, the processing temperature that it can sustain is still limited at a maximum temperature of 350–400 °C . Therefore, to realize the flexible AMOLEDs, TFT backplanes with a maximum processing temperature within 400 °C (or even lower) should be developed.…”
Section: Fabrication Of Flexible Amoledsmentioning
-Developments of backplane technologies, which are one of the challenging topics, toward the realization of flexible active matrix organic light-emitting diodes (AMOLEDs) are discussed in this paper. Plastic substrates including polyimide are considered as a good candidate for substrates of flexible AMOLEDs. The fabrication process flows based on plastic substrates are explained. Limited by the temperature that plastic substrates can sustain, TFT technologies with maximum processing temperature below 400 C must be developed. Considering the stringent requirements of AMOLEDs, both oxide thin-film transistors (TFTs) and ultra-low-temperature poly-silicon TFTs (U-LTPS TFTs) are investigated. First, oxide TFTs with representative indium gallium zinc oxide channel layer are fabricated on polyimide substrates. The threshold voltage shifts under bias stress and under bending test are small. Thus, a 4.0-in. flexible AMOLED is demonstrated with indium gallium zinc oxide TFTs, showing good panel performance and flexibility. Further, the oxide TFTs based on indium tin zinc oxide channel layer with high mobility and good stability are discussed. The mobility can be higher than 20 cm 2 /Vs, and threshold voltage shifts under both voltage stress and current stress are almost negligible, proving the potential of oxide TFT technology. On the other hand, the U-LTPS TFTs are also developed. It is confirmed that dehydrogenation and dopant activation can be effectively performed at a temperature within 400 C. The performance of U-LTPS TFTs on polyimide is compatible to those of TFTs on glass. Also, the performance of devices on polyimide can be kept intact after devices de-bonded from glass carrier. Finally, a 4.3-in. flexible AMOLED is also demonstrated with U-LTPS TFTs.
“…But, perhaps, optical transparency at very high processing temperature is arguably the primary requirement. As an example, in the fabrication of flexible active matrix organic light emitting display devices (AMOLEDs), the processing temperature on the flexible polymer film substrates could be higher than 300 °C …”
Recently, colorless and transparent plastic substrates with high glass transition temperature and suitable thermo‐mechanical properties are in high demand in optoelectronic device industries, due to their various optical applications. Colorless polyimides (CPIs) exhibit both high thermo‐mechanical stability as well as high transparency that are suitable for optoelectronic applications. The most recent (2010–2018) developments on CPIs, in terms of design and synthesis of new monomers and their effects on the thermo‐optical properties of the obtained CPIs, are reviewed in this article.
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