17.3: Highly Efficient Fluorescent/Phosphorescent OLED Devices Using Triplet Harvesting

Kondakova, Marina; Giesen, David J.; Deaton, Joseph C.; Liao, Liang‐Sheng; Pawlik, Thomas D.; Kondakov, Denis Y.; Miller, Michael E.; Royster, Tommie L.; Comfort, Dustin L.

doi:10.1889/1.3069627

Cited by 8 publications

(3 citation statements)

References 8 publications

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“…Hence, there is a high need to find alternatives to the all‐phosphorescent approach, which avoid the use of unstable blue phosphorescent emitters, but still keep the potential of a 100% IQE. One alternative is the triplet‐harvesting approach 106–112.…”

Section: Oleds With Doped Transport Layersmentioning

confidence: 99%

Doping of organic semiconductors

Lüssem

Riede

Leo

2012

Physica Status Solidi (a)

536

542

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The understanding and applications of organic semiconductors have shown remarkable progress in recent years. This material class has been developed from being a lab curiosity to the basis of first successful products as small organic LED (OLED) displays; other areas of application such as OLED lighting and organic photovoltaics are on the verge of broad commercialization. Organic semiconductors are superior to inorganic ones for low‐cost and large‐area optoelectronics due to their flexibility, easy deposition, and broad variety, making tailor‐made materials possible. However, electrical doping of organic semiconductors, i.e. the controlled adjustment of Fermi level that has been extremely important to the success of inorganic semiconductors, is still in its infancy. This review will discuss recent work on both fundamental principles and applications of doping, focused primarily to doping of evaporated organic layers with molecular dopants. Recently, both p‐ and n‐type molecular dopants have been developed that lead to efficient and stable doping of organic thin films. Due to doping, the conductivity of the doped layers increases several orders of magnitude and allows for quasi‐Ohmic contacts between organic layers and metal electrodes. Besides reducing voltage losses, doping thus also gives design freedom in terms of transport layer thickness and electrode choice. The use of doping in applications like OLEDs and organic solar cells is highlighted in this review. Overall, controlled molecular doping can be considered as key enabling technology for many different organic device types that can lead to significant improvements in efficiencies and lifetimes.

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Section: Oleds With Doped Transport Layersmentioning

confidence: 99%

Doping of organic semiconductors

Lüssem

Riede

Leo

2012

Physica Status Solidi (a)

536

542

View full text Add to dashboard Cite

show abstract

“…Hence, there is a high need to find alternatives to the all-phosphorescent approach, which avoid the use of unstable blue phosphorescent emitters, but still keep the potential of a 100% IQE. One alternative is the triplet-harvesting approach [106][107][108][109][110][111][112].…”

Section: Review Articlementioning

confidence: 99%

Doping of Organic Semiconductors

Lüssem

Riede

Leo

2012

Physics of Organic Semiconductors

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Björn Lü ssem studied electrical engineering at the Rheinisch-Westfälische Technische Hochschule (RWTH) in Aachen and the University of Bath and obtained his degree as Diplomingenieur in 2003. He prepared his PhD thesis at the Research Center in Jülich, Germany, in the field of molecular electronics. His thesis concentrates on scanning tunneling microscopy of pure and mixed selfassembled monolayers and has been awarded the VDE-Promotionspreis and the Günther-Leibfried-Preis. After staying at the Materials Science Laboratory of Sony in Stuttgart from 2006 to 2008, he joined Prof. Leo's group at the Technische Universität Dresden where he is now the head of the New Devices Group. His main interests are new semiconducting devices based on organic materials and their differences or similarities to inorganic semiconductors. Moritz Riede studied physics at the University of Cambridge, UK, where he received his MSc degree in 2002. He obtained his PhD degree from the University of Konstanz in 2006 for research carried out at the Fraunhofer-Institut für Solare Energiesysteme and the Freiburger Materialforschungszentrum FMF. The focus of his thesis was on solution-processed organic solar cells. After his PhD he joined the research group of Prof. Leo at the Institut für Angewandte Photophysik (IAPP) of the Technische Universität Dresden in 2007, where he is now head of the Organic Solar Cell Group. His research concentrates on small-molecule-based organic solar cells, their fundamental working principles, and strategies for device optimization. Karl Leo obtained the Diplomphysiker degree from the University of Freiburg in 1985, working with Adolf Goetzberger at the Fraunhofer-Institut für Solare Energiesysteme. In 1988, he obtained the PhD degree from the University of Stuttgart for a PhD thesis performed at the Max-Planck-Institut für Festkörperforschung in Stuttgart under the supervision of Hans Queisser. From 1989 to 1991, he was a postdoctoral researcher at AT&T Bell Laboratories in Holmdel, NJ, USA. From 1991 to 1993, he was with the Rheinisch-Westfälische Technische Hochschule (RWTH) in Aachen, Germany. Since 1993, he has been full professor of optoelectronics at the Technische Universität Dresden. Since 2002, he is also with the Fraunhofer society, currently as director of Fraunhofer COMEDD. His main current interests are novel semiconductor systems such as semiconducting organic thin films, with special emphasis to understand growth, basic device principles, and the optical response. Recently, he has also worked on device development, such as highly efficient organic LED and solar cells. His work was recognized by several awards, including the Leibniz-Award in 2002. He was involved in the founding of several companies such as Novaled AG and Heliatek GmbH. Figure 1 Operation principles of an OLED (left) and an OSC (right). Two-layer devices are shown. Reprinted with permission from Walzer et al., Chem. Rev. 107, 1233 (2007).

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“…The triplet energy level of a fluorescent layer is generally lower than that of a phosphorescent layer; consequently, triplet excitons in the phosphorescent layer are quenched, resulting in decreased efficiency. Although triplet harvesting has been proposed for use in a single-unit hybrid OLED to prevent such quenching [6], increases in efficiency and lifetime have not yet been achieved.…”

Section: Introductionmentioning

confidence: 99%