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Introduction: Special Section on OLEDs

During the past 15 years, research and development on organic light-emitting diodes (OLEDs) has been spectacular. Flatpanel displays using OLEDs are gradually moving from niche to mainstream applications and their market is predicted to reach several billion dollars by 2009. High-resolution displays, however, represent only a small fraction of new consumer products that can be envisioned with the advent of low-cost highly flexible displays. Hence, even better times for OLED displays and light sources have yet to come. This Special Section on OLEDs in the Journal of the Society for Information Display illustrates the vibrant activities in this field. The breadth and the depth of the contributions in this Special Section from world-class experts show the multiple facets of this technology and highlights its multidisciplinary nature. Continuous enabling advances are made in areas ranging from the theoretical modeling of the fundamental aspects of electroluminescence to improvements in organic semiconductors, light-emitting materials, and transparent conducting oxides to the design of novel architectures for display drivers. Materials and devices are continuously gaining in efficiency and stability, display prototypes exhibit ever-increasing resolution, lower power consumption, increased operational lifetimes, lower manufacturing cost, and higher production yields. The recent release by Samsung Electronics of a 21-in.-diameter 1920 × 1080 wide ultra-extended graphics array (WUXGA) activematrix OLED display (AMOLED) exemplifies the future potential of this technology. The timing of the publication of this Special Section on OLEDs in the Journal of the Society for Information Display (JSID) coincides with several other major changes in the Journal: first year of on-line and monthly publication; listing in the peer-reviewed journal databases such as Scitations, SPIN, and INSPEC. Covering OLEDs in some depth is thus another step aimed at better serving the needs of the members of the Society for Information Display. The readers of this Special Section will find a comprehensive overview of original advances made recently in OLED science and technology. On page 383, Prof. Tobin Marks et al. (Northwestern University) describes recent advances in transparent conducting oxides (TCOs). His work illustrates that alternatives to indium tin oxide (ITO), the current workhorse of TCOs in the display industry, are around the corner. Because the cost of indium is high due to its limited availability, new materials such as doped CdO might provide future lower-cost solutions with simultaneously improved stability. The passive-matrix displays described on page 389 by OSRAM Opto Semiconductors, Inc., exemplify the continuous technological improvements in OLED displays based on polymers that can be processed from solution. Having projected luminance half-lifetimes of 40,000 hours at room temperature, polymer electroluminescent displays are becoming more stable and are likely to find an increasing number of new applications in handheld electronic products. On page 393, Prof. Karl Leo et al. (Technical University of Dresden and Novaled GmbH) reports on OLEDs with unprecedented power efficiencies and stability. By sandwiching an intrinsic electrophosphorescent material between pand n-doped materials, extremely high light output is achieved at low operating voltage, resulting in power efficiencies of nearly 70 lm/W at luminance levels of 1000 cd/m2. These impressive results are achieved without specific light-extraction mechanisms. In view of the important fraction of light that is trapped in the films by total internal reflection, it is likely that even larger efficiencies are yet to be demonstrated in the near future. These advances show the potential of these technologies in efficient solid-state lighting. Continuous progress in new material development is illustrated through the work of Prof. Shirota et al. (Osaka University) on page 399 and that of Prof. Thompson (University of Southern California, and City University of Hong Kong) on page 405. Studies on interface engineering by Prof. Yang (University of California, Los Angeles) on page 411 remind us of the importance of interfaces formed between organic materials and hybrid interfaces between organics and metals. Finally, one should reflect on the importance of the theoretical understanding of the fundamental processes behind OLED technology such as charge injection, charge transfer, radiative/non-radiative recombination. The contribution of Prof. Bredas et al. (Georgia Institute of Technology and University of Mons-Hainaut) on page 419 provides a comprehensive overview of the latest developments in this area. Several contributed papers on various aspects of the science and engineering of OLEDs complete this special issue. They are a testimony of the activity in this field. Finally, we would like to acknowledge our colleagues who served as reviewers for these contributed and invited papers, as well as the editorial staff of the Journal of SID for their help in assembling this Special Section. Special thanks go to Dr. Andras Lakatos, his leadership and advise have been helpful to us during the preparation of this publication.