場所：9号館2階 会議室 200-1
題目：Alternative transparent electrodes for organic light emitting diodes
Solid state lighting is a new environmentally friendly light source.
So far, light emitting diodes (LEDs) and organic LEDs (OLEDs) have been presented as candidates with potentially high efficiency. Recent advances of OLEDs have ensured high efficiency, exceeding that of incandescent light bulbs. In contrast to conventional point source
LEDs, OLEDs distribute light throughout the surface area and are not restricted by their size. Additionally, OLEDs are expected to reach sufficient stability in the near future. The remaining challenge for OLEDs is their cost. New OLED technologies provide cost effective manufacturing methods which could be presented for transparent electrode materials because indium tin oxide (ITO), a widely used material as a transparent electrode for OLEDs, is less than optimal
due to its high element price.
In this work, alternative transparent electrodes for OLEDs as a replacement of ITO were studied. First, Al doped ZnO (ZnO:Al) which is composed of abundant materials was investigated with DC magnetron sputtering under a wide range of experimental conditions. The optimised ZnO:Al received comparable performance with conventional ITO films, low sheet resistance as well as a high transparency. Various type of p-i-n OLEDs were employed on the structured ZnO:Al using
photolithography. It has been found that the OLEDs on ZnO:Al anode has comparable or better device efficiencies and operational lifetime compared to OLEDs on conventional ITO anode. As another alternative electrode, the conductive polymer Baytron®PH510 (PEDOT:PSS) was
investigated. Due to a relatively high sheet resistance of PEDOT:PSS, metal grid was designed for large size OLEDs. Up-scaled devices on 10 × 10 cm2 using PEDOT anode were also demonstrated. These results showed ZnO:Al and PEDOT are suitable for OLEDs as anode and have high potential as alternative transparent electrode materials.