Bernard Kippelen
Professor, Electrical and Computer Engineering | Georgia Tech College of Engineering
Atlanta, GA, UNITED STATES
Bernard Kippelen is an expert in polymer optics and plastic electronics.
Media
Publications:
Documents:
Photos:
Videos:
Audio/Podcasts:
Biography
Dr. Kippelen was born and raised in Alsace, France. He studied at the University Louis Pasteur in Strasbourg where he received a Maitrise in Solid-State Physics in 1985, and a Ph.D. in Nonlinear Optics in 1990.
From 1990 to 1997 he was Chargé de Recherches at the CNRS, France. In 1994, he joined the faculty of the Optical Sciences Center at the University of Arizona. There, he developed a research and teaching program on polymer optics and plastic electronics. In August 2003, Dr. Kippelen joined the School of Electrical and Computer Engineering at the Georgia Institute of Technology where his research ranges from the investigation of fundamental physical processes (nonlinear optical activity, charge transport, light harvesting and emission), to the design, fabrication and testing of light-weight flexible optoelectronic devices and circuits based on nanostructured organic materials. He served as Director of the Center for Organic Photonics and Electronics (COPE) from 2011-2019. He currently serves as co-President of the Lafayette Institute, a major optoelectronics commercialization initiative that is based at Georgia Tech-Lorraine in Metz, France.
He currently holds 25 patents and has co-authored over 270 refereed publications and 14 book chapters. His publications have received over 20,000 citations and his h-index is 73 (Google Scholar). He served as chair and co-chair of numerous international conferences on organic optoelectronic materials and devices and as deputy editor of Energy Express. He was the founding editor of Energy Express.
Areas of Expertise (4)
Organic Photodetectors and Sensors
Optics and Photonics
Nanotechnology
Printed Electronics
Selected Accomplishments (2)
NSF CAREER Award
NSF CAREER Award
3M Young Faculty Award
3M Young Faculty Award
Education (1)
University Louis Pasteur: Ph.D., Philosophy 1990
Affiliations (5)
- Optical Society of America
- American Chemical Society
- American Physical Society
- Materials Research Society
- International Society for Optical Engineering
Selected Media Appearances (2)
Nano From The Forest
The Biological SCENE online
2014-06-30
And in another electronics advance, researchers recently showed for the first time that organic solar cells fabricated on cellulose nanocrystal substrates can convert nearly 3% of sunlight to electricity. That efficiency is much lower than that of other types of solar cells, but it is in line with those of organic solar cells, which are attractive because of their low cost. The research team, which includes Bernard Kippelen of Georgia Institute of Technology, Robert J. Moon of FPL and Purdue University, and coworkers, demonstrated that nanocellulose-supported solar cells can be easily separated into their components and recycled with minimal energy input owing to nanocellulose’s biodegradability. That feature offers a distinct cost and environmental life-cycle advantage compared with the petroleum-based substrates used in conventional organic solar cells ..
Digital lighting goes organic
Science News for Students online
2014-06-06
And OLEDs emit light in all directions. This quality makes OLEDs ideal for display screens as well as lighting, says Bernard Kippelen. He heads a center in Atlanta at the Georgia Institute of Technology where experts research OLEDs and other organic electronics. It’s called the Center for Organic Photonics and Electronics (COPE)...
Patents (3)
High glass transition temperature "medium-sized" ambipolar host materials
WO2014011477A1
2013 Disclosed herein are am bipolar host compounds represented by formula (I), wherein: a) R4 is an optionally substituted aryl or an optionally substituted heteroaryl group; b) n is at least 2; e) for each (ii) at least one of R1, R2 and R3 is independently an optionally substituted carbazole group, and the remaining of R1, R2 and R3 are independently selected from hydrogen, halogen and a C1-20 organic group: and d ) Y is selected from (III), wherein R5 is an.optionally substituted aryl group, an optionally substituted heteroaryl group, an optionally substituted alkyl group or an optionally substituted heteroalkyl group, and wherein R6 is hydrogen,, an optionally substituted aryl group, an optionally substituted heteroaryl group, an optionally substituted alkyl -group or an optionally substituted heteroalky! group. The compounds can be used in OLED devices and are ambipolar. The OLED devices can show high efficiency and high luminance.
Polymerizable ambipolar hosts for phosphorescent guest emitters
US20120172556A1
2010 The inventions describe disclosed and described herein relate to polymerizable ambipolar monomers, useful for making polymer or copolymer host materials for guest phosphorescent metal complexes, which together can form emission layers of organic light emitting diodes (OLEDs). Methods of making the ambipolar monomers are also described. Formula (I) wherein at least one of the R1, R2 and R3 groups is an optionally substituted carbazole group.
Stable electrodes with modified work functions and methods for organic electronic devices
US8586208B2
2008 A device includng an electrode, the electrode having a surface; a molecule bound to the surface of the electrode through a binding group; an organic electronic material in electrical contact with the electrode, wherein the molecule comprises at least one fluorinated aryl group, wherein the electrode contains a transparent conductive metal oxide, a carbon nanotube, or graphene.
Selected Articles (5)
Morphology of Organic Semiconductors Electrically Doped from Solution Using Phosphomolybdic Acid
Chemistry of Materials2019 The field of organic electronics aspires to enable the fabrication of low-cost, solution-processed optoelectronic devices with unique mechanical, electrical, optical, and chemical properties. Critical to the success of these aspirations is the ability to fabricate controlled doping profiles vertically or laterally (i.e., to a limited depth or area extension). However, the fabrication of stable doping profiles in polymer films has proven particularly challenging, as neither solution processing nor evaporation of dopants, such as 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ), leads to vertical doping profiles due to fast diffusion on the length scale of the typical film thickness (∼100 nm). This challenge was surmounted in 2017 with the first demonstration of a successful solution-based technique to fabricate doping profiles in semiconducting polymer films through immersion into a phosphomolybdic acid (PMA) solution (Kolesov et al., 2017). Still, to date, no clear picture that explains the doping phenomena has emerged. In an attempt to identify some of the key variables that govern the PMA doping process and shed light onto why this technique produces vertical doping profiles in organic films, we here report on a study of the morphology of PMA doped semiconducting polymer films, complemented theoretically with ab initio quantum chemistry calculations. We believe these results may foster the extension of the technique to other organic optoelectronic systems.
A Simple and Efficient Solution-Based Technique to Electrically Dope Organic Semiconductors
The Electrochemical Society2019 The printed electronics industry offers a paradigm change in manufacturing, cost and environmental impact when compared to the conventional semiconductor industry. Printed electronic devices are expected to be mass-produced from less-energy-demanding processes over large areas and on flexible substrates, with techniques that closely resemble the well-known mass production of printed media on paper. Still, critical to the widespread of these devices is the ability to convert lab produced “champion” figures into reliable industrial-scale products. The well-established strategies for the design and fabrication of efficient lab-scale printed electronics are not always compatible with large-area manufacturing, where several additional requirements must be met. Solution-based electrical doping of organic semiconductors has received increased attention as a technique with the potential to comply with some of these additional requirements. Stable ink-type formulations of dopant, semiconductor and solvents have been reported, some of which may be compatible with roll-to-roll coating. Yet, the ability to fabricate vertical doping gradients, critical to maintain optimal optoelectronic performance at reduced cost, has proven challenging. Vertical doping gradients would reduce the amount of coating steps without a loss in optoelectronic device functionality, simplifying manufacturing and preventing defects to propagate.
Optimizing Crack Onset Strain for Silicon Nitride/Fluoropolymer Nanolaminate Barrier Films
Applied Nano Materials2019 Nanolaminates using alternating inorganic and organic layers have the potential to provide ultrabarrier with high resistance to gas permeation while also changing the crack onset strain (COS) to improve mechanical reliability. Previous modeling efforts highlighted the possibility to achieve an optimized design depending on thickness and material properties (elastic modulus, fracture energy), producing the highest possible value of COS. In this study, we experimentally show that the optimization can be achieved using SiNx/CYTOP laminates when guided by theoretical predictions. Nanolaminates using silicon nitride (SiNx) inorganic films and CYTOP organic films were fabricated. The fracture energy of the CYTOP layer was found to be 90 ± 10 J/m2. A 50% increase in COS (from 1.7 to 2.5%) was experimentally measured as a result of the thickness ratio optimization for a 3-layer structure consisting of two 30 nm thick SiNx layers and one 33 nm thick CYTOP layer. In the same way, a 70% increase in COS (from 1.7 to 2.8%) was measured for a 5-layer structure consisting of three 20 nm thick SiNx layers and two 25 nm thick CYTOP layers. The numerical results also showed that a 45%, 73%, 110%, and 160% increase in COS can be obtained in 3-, 5-, 9-, and 19-layer structures, respectively, if the total thickness ratio of CYTOP to SiNx layer is at the optimized value, i.e., ∼0.55, 0.83, 2.67, and 9, respectively. The same procedure can be applied to all inorganic/organic multilayered films to find the optimized COS, including the measurement of high fracture energy of organic layers, enabling the design of mechanically robust permeation barriers for flexible electronics.
Host-Free Yellow-Green Organic Light-Emitting Diodes with External Quantum Efficiency over 20% Based on a Compound Exhibiting Thermally Activated Delayed Fluorescence
ACS Applied Materials & Interfaces2019 Thermally activated delayed fluorescent (TADF) materials are advantageous as emitters in organic light-emitting diodes (OLEDs) due to their ability to utilize all excited states formed by charge recombination for light emission, potentially leading to 100% internal quantum efficiency. As in conventional fluorescent or phosphorescent OLEDs, TADF emitters are commonly doped at a relatively low concentration in a host matrix. However, increasing evidence suggests that balanced ambipolar transport properties and small aggregation-induced fluorescence quenching allow TADF emitters to be used alone in so-called host-free OLEDs. Here, we report host-free OLEDs in which the emissive layers (EMLs) consist solely of a yellow-green-emitting TADF compound, 5,5′-(2,3,5,6-tetra(carbazol-9-yl)-1,4-phenylene)bis(2-(4-(tert-butyl)phenyl)-1,3,4-oxadiazole), TCZPBOX. Devices with this host-free EML yield a maximum external quantum efficiency (EQE) of 21%, current efficacy (CE) of 73 cd/A, and power efficacy (PE) of 79 lm/W at a luminance of 10 cd/m2. At a high luminance of 10,000 cd/m2, a high EQE of 13% is maintained. A maximum luminance of 120,000 cd/m2 is reached at an applied voltage of 9.8 V. When TCZPBOX was doped in the host 2,6-di(carbazol-9-yl)-pyridine (PYD2) at 40 wt %, the device yielded a maximum EQE of 28%, CE of 94 cd/A, and PE of 100 lm/W at 10 cd/m2.
Organic materials and devices for next-generation imaging applications (Conference Presentation)
International Society for Optics and Photonics2019 Printable organic solid-state devices, including organic light-emitting diodes (OLEDs) and organic thin-film transistors (OTFTs) present a paradigm shift in manufacturing, cost and environmental impact when compared to the conventional inorganic technologies. OLEDs offer great versatility in the design of lighting systems based on large-area diffused light sources. In recent years, smarter lighting concepts have emerged at the crossroad of display technology and lighting that enable the control of the spatial distribution of light in real time. This adaptive illumination is enabled by combining segmented OLEDs with OTFTs. For these concepts to come to fruition, it is critical that further advances be made in improving the efficacy and stability of OLEDs and simultaneously in enhancing the performance and reliability of OTFTs. In this talk, we will discuss recent advances in developing new thermally activated delayed fluorescent materials and recent progress in OTFTs. In particular, we report on an exhaustive characterization of OTFTs with an ultra-thin bilayer gate dielectric comprising the amorphous fluoropolymer CYTOP and an Al2O3: HfO2 nanolaminate. The bilayer geometry results in two distinct aging mechanisms that through a compensation effect, yields devices with very low threshold voltage shifts. Modeling with a double stretched-exponential model predicts threshold voltage shift values in the range of 0.1 – 0.25 V over a period of ten years even at temperatures of 55 °C. The microcrystalline OTFTs with a bilayer gate dielectric exhibit carrier mobility values up to 1.6 cm2 V-1 s-1, a threshold voltage stability that is comparable or superior to that expected from commercial TFT technologies, and excellent environmental and thermal stability even after prolonged immersion in water.
Social