Ramon Springer joined the group of Prof. Jang Hyuk Kwon (Department of Information Display, Kyung Hee University, South Korea) to carry out a Master thesis topic within the international Masters course Organic and Molecular Electronics (OME) at the TU Dresden. His thesis task was to develop a white-light emitting, multiple OLED stack based on blue and yellow units to be used in AMOLED displays. Here, aside from the optimization of device efficiency, the color quality and angular stability were parameters to be optimized. His work led to a recent publication in Optics Express entitled “Cool white light-emitting three stack OLED structures for AMOLED display applications“. Congratulations to a very successful research stay abroad.
Our new paper entitled “Adjustable white-light emission from a photo-structured micro-OLED array” published in Light: Science & Applications discusses an approach towards micro-OLED arrays made of differently emitting sub pixels without non-emissive areas. This is achieved using orthogonal lithography techniques in a way that only the first OLED unit is structured while the next one to follow is made in a “fill-the-gap” approach. In this conceptual demonstration, we pair blue and yellow OLEDs in a stripe layout, which can be addressed individually for complete color tunability. Feature sizes of the stripes are down to 20 micrometer.
The Journal of Solid State Lighting welcomes submissions to the new thematic series on OLED Materials for Lighting.
Over the past three decades, organic light-emitting diodes (OLEDs) have attracted much attention due to their potential applications in displays and lighting. As promising candidates for lighting applications, OLEDs have several advantages compared with established light sources, such as incandescent bulbs, fluorescent tubes or inorganic LEDs: they are flat area emitters offering pleasant diffuse light perception, wide viewing angles, vivid colors, light and thin luminaires, and the possibility to be made transparent or to be processed on flexible substrates by low cost processing. At present, white OLEDs are capable of achieving a lifetime of more than 200 Khrs, the power efficiency of OLEDs has reached over 100 lm/W, and OLED luminaires are now available for domestic use. However, there is still a long way before we reach the goal of making OLED light sources with great lifetime and efficiency at low cost. In view of this, the potentially large market for OLEDs is driving both the academic and industrial community towards the development of new materials and advanced device manufacturing technologies.
We are inviting authors to contribute original research articles with a focus on OLED materials for lighting.
Potential topics include, but are not limited to:
- Developments of novel red, yellow, green, blue emitter materials (fluorescence, phosphorescence, thermally activated delayed fluorescence) for white OLEDs
- Development of high efficiency single-white polymers for white OLEDs
- Development of transport and matrix materials suitable for white OLEDs
- Emitter orientation
- Interconnect technologies (charge generation layers, interstack-electrodes)
- Substrates and electrodes for flexible devices
- Light outcoupling approaches through novel material design
- Materials for improved OLED stability
- Advanced material modelling for OLEDs
- Low cost OLED material production
- Quantum dot/organic hybrid materials for white OLEDs
Before submitting your manuscript, please ensure you have carefully read the Instructions for Authors for Journal of Solid State Lighting. The complete manuscript should be submitted through the Journal of Solid State Lighting submission system. To ensure that you submit to the correct thematic series please select the appropriate section in the drop-down menu upon submission. In addition, indicate within your cover letter that you wish your manuscript to be considered as part of the Thematic Series on OLED Materials for Lighting. All submissions will undergo rigorous peer review and accepted articles will be published within the journal as a collection.
Deadline for submissions:
March 31st, 2016
Lead Guest Editor
Dongge Ma, State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, P. R. China
Sebastian Reineke, Institut fuer Angewandte Photophysik, Technische Universitaet Dresden, 01062 Dresden, Germany
Lian Duan, Department of Chemistry, Tsinghua University, PR China
Submissions will also benefit from the usual benefits of open access publication:
• Rapid publication: Online submission, electronic peer review and production make the process of publishing your article simple and efficient
• High visibility and international readership in your field: Open access publication ensures high visibility and maximum exposure for your work – anyone with online access can read your article
• No space constraints: Publishing online means unlimited space for figures, extensive data and video footage
• Authors retain copyright, licensing the article under a Creative Commons license: articles can be freely redistributed and reused as long as the article is correctly attributed
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In our new paper published in Applied Physics Letters entitled “White organic light-emitting diodes with 4 nm metal electrode“, we report on white OLEDs with ultra thin metal electrodes that replace ITO for the better. With close layers of only 4 nm thickness, the overall optical properties of these composite electrodes approach the ITO standard electrode system, whereas their mechanical performance is by far superior. Such electrodes are highly flexible and, in addition, allow for fabrication at any position within the vertical layer structure. Thus, their use is not limited to the bottom electrode function, but also they can be used as interconnects and/or transparent top electrodes.
In a new review article (Recent advances in light outcoupling from white organic light-emitting diodes) in the Journal of Photonics for Energy, my colleague Malte C. Gather (University of St. Andrews) and I summarize the recent efforts on the development of concepts for light outcoupling in white organic light-emitting diodes (OLEDs). Especially with respect to the complementary inorganic LED technology, it is extremely important to unlock higher external quantum efficiencies in OLEDs to stay competitive. Here, improving the outcoupling efficiency by far offers the largest margin (standard structures are at 20-30% of the internal efficiency maximum). The current status reveals that a universal solution with satisfying enhancement still waits to be found.
The May (2015) issue of Nature Materials contains a ‘focus on LED technology‘, surely motivated by the UNESCO International Year of Light 2015 and the Nobel Prize in Physics 2014 acknowledging the discovery of highly efficient blue gallium nitride (GaN) light-emitting diodes (LEDs). The latter actually set the basis for the current revolution in lighting technology we all witness.
But there is more than just LEDs made from inorganic semiconductors like GaN (an more complex GaN-based ternary alloys), which produces white light when paired with downconversion phosphor materials. LEDs made from organic semiconductors (OLEDs) or quantum dots (QD-LEDs) are alternative, high efficiency device concepts that offer to participate in the transition to an all solid-state light source future. I got a chance to comment on both technologies in the above mentioned Nature Materials focus (Complementary LED technologies). With respect to all major LED technologies (LED, OLED, and QD-LED), if there is one thing that I wish we will see in future is the coexistence of all different concepts, where each application is further advanced by the most suitable architecture.
The above mentioned paper has finally shaped to its final form. White organic light-emitting diodes: Status and perspective has been published today in Reviews of Modern Physics (RMP). It contains more than 40 pages of densely packed details on white OLEDs including the main concepts of realizing white emission (from both polymers and/or small molecules), in depth discussions of respective efficiency limits, and promising strategies for enhanced light outcoupling. Here is an editorial summary (source RMP):
The conversion of electricity into a photon flux with color quality resembling natural sunlight is desirable for artificial illumination. The ubiquitous incandescent light bulb, introduced in 1880 by Thomas Edison, satisfies this color quality requirement but suffers from a rather poor energy conversion efficiency of approximately 5%. This review focuses on device strategies to produce efficient organic white light-emitting diodes based on small molecular and polymeric semiconductors, which in the context of next generation lighting have a considerable technological promise.
If you like it, please spread the word. Here is an exciting side note: This paper is published in the same issue of RMP that also contains the great Nobel lectures of Serge Haroche and David J. Wineland, who share the 2012 Nobel Prize for Physics. Another good reason to check out the current issue of RMP.