||In order to obtain an anode with flexibility and high conductivity, lots of groups try to enhance the conductivity of PEDOT:PSS with adding polar solvents─such as glycol, ethanol and using post-treatment by immersing acid, dopant solvents and dipping process. These results show that, by varying the arrangement and ratio between PEDOT and PSS, those three different ways are all can enhance the conductivity more than four orders. In recent years has been measured and confirmed.|
In this research, we use the polar aprotic solvents to treat the PEDOT:PSS solution and film by doping and dipping treatment. Through optimization of the parameters, we can effectively enhance the conductivity of PEDOT:PSS from 0.3 to 718 S/cm and 1255 S/cm by an easy, stable, fast and height adaptation method. Four orders of conductivity can be enhanced. The films with different treatment were investigated and compared with each other in the difference of optical conductivity, transmittance, work function, surface roughness, surface morphology, and stability. The films also use XPS and UV-vis absorption to analyze the conductivity enhancement mechanism. When the doping and dipping treatment PEDOT:PSS as anode of device at the luminance of 1000 cd/m2, the performance of current efficiency are 20.8 cd/A and 15.4 cd/A, power efficiency are 6.7 lm/W and 6.3 lm/W and EQE are 9.7% and 7.7%.
In this other side of study, we fabricated organic light-emitting diodes (OLEDs) with internal light extraction structure by using the plastic substrate with photonic quasi crystals (PQC) and moth eye anti-reflection structure (AR) provided by Industrial Technology Research Institute (ITRI) of Taiwan. Anodes fabrication and design of OLED device structure are optimized so that the optical losses inside the OLEDs with internal light extraction structure are minimized and light extraction efficiency of the OLEDs are enhanced. The study was divided into five stages:
1. The transmittance and morphology of PQC and AR nanostructure were measured and studied.
2. High refractive index material spin coated onto PQC and AR substrates as filled layer, then sputter-deposited of Indium Tin Oxide (ITO). The transmittance, morphology and sheet resistance of PQC and AR nanosubstrates covered by filled layer and ITO were measured and studied. And then, design and fabrication of ITO anodes were performed.
3. The optimized standard blue and green OLED device structures were chosen to fabricate green and blue OLEDs with internal light extraction structure. The opto-electrical properties of the devices were measured and studied.
4. The transmittance and morphology of AR on PET substrate were measured and studied.
5. The optimized standard blue and white OLED device structures were chosen to fabricate blue and white flexible OLEDs with internal light extraction structure. The opto-electrical properties of the devices were measured and studied.
Finally, we successfully fabricated blue OLEDs with PQC structure and green OLEDs with AR structure respectively. The blue and green OLEDs with internal light extraction structure have outstanding light extraction efficiency, which increase the external quantum efficiency (EQE) by 45.9% and 19.8% compared to standard OLEDs at 1000cd/m2 respectively, and we fabricated blue and white FOLEDs with internal light extraction AR nanostructure with ITO anode. Significantly, the white flexible OLEDs with internal light extraction structure have outstanding light extraction efficiency, which increase the external quantum efficiency (EQE) by 27.8% compared to white OLEDs on PET substrates at 1000 cd/m2. We also proposed various methods to improve light extraction efficiency of OLEDs.