The Kippelen Research Group is responsible for significant advancements in carbon-based nanomaterial research, creating new devices and new methods for optic and photonic applications. One major innovation from Dr. Kippelen’s materials research is the revolutionary method of creating stable, low-work function electrodes — electrodes that easily inject electrons into devices. The result: organic optoelectronic semiconductor devices with increased longevity and reliability.

The 2000 Nobel Prize in Chemistry award for the discovery and development of conductive polymers provided an opportunity to revolutionize the field of electronics. It enabled the manufacture of extremely thin and flexible electronic components and circuits for printing or depositing onto virtually any surface. Dr. Kippelen’ s work vastly expanded the possibilities in this emerging area through the development of organic semiconductor devices. 

For instance, the development of a simple method to lower the work function of electrically conducting polymers was the breakthrough that allowed the Kippelen Research Group to fabricate the first, all-organic solar cell from solution, using standard printing techniques. Organic photovoltaic devices exhibit high efficiency, durability, flexibility, and can be manufactured at a lower cost than their silicon-based counterparts. The impact of this technology is critical to improving the economic viability of the renewable energy sector and advancing printable electronics.

The development of organic semiconductors also enabled the emergence of organic light-emitting diode (OLED) technology for display and lighting applications. The Kippelen Research Group incorporated new organic semiconductors into OLED devices, creating new device architectures to greatly improve the image quality and energy efficiency of products such as smartphones, TV screens, displays, wearable electronics, cameras, and lighting installations.

Another notable development is a method to produce a dual-layer gate, organic thin-film transistor (OTFT) that improves stability for enhanced performance in devices that include sensors, wearable and flexible electronics, and artificial neural networks.

Research Achievements 

• Advanced Artificial Lighting: Based on the discovery that photodetectors in the human eye are sensitive to the ambient light spectrum, the group developed an artificial light source to mimic the color variations of natural light, which are critical in maintaining circadian rhythms that regulate human metabolic activity. In settings where humans are not exposed to enough natural light, this patent-pending technology has the potential to improve physical and mental well-being. This invention also has the potential to transform the indoor lighting market. Georgia Tech’s Office of Technology Licensing is actively pursuing industry partnerships to develop and commercialize products incorporating this technology.
• OLED Technology Advancement: Using the new methods and materials developed by its collaborators, the Kippelen Research Group has produced numerous devices to continually improve OLED technology. The impact is immeasurable as these devices are integrated into high-volume use products such as TVs, cell phones, and computers.
• Organic Photovoltaic (Solar) Cells: Dr. Kippelen’s group fabricated the first all-organic solar cell using standard printing techniques. These plastic-based cells underwent further development to allow printing on paper to address environmental concerns with plastic use and disposal. The result is a lightweight, flexible, recyclable, low-cost solar cell with application in consumer electronics, building design and construction, the Internet of Things, and integration into textiles and garments.
• Organic Thin Film Transistors: The team developed a process to fabricate a dual-layer gate geometry that allows a device’s architecture to “age” simultaneously, nearly eliminating threshold voltage shifts, a major source of degradation in device operation. This may lead to wider use of organic thin-film transistors, crucial to the advancement of printed electronics.
• Organic Photodiodes: These photodiodes are created with organic semiconductors for the detection of very low light levels. They attain performance equal to industry-leading silicon-based detectors. 

Activities

Dr. Kippelen’s work spans wide-ranging developments in the field of organic, flexible electronics, including more than 50 inventions. In addition to advancements in photoelectronic devices (LEDs, solar cells, etc.) and the use of unique materials with useful electronic properties, the list below provides some highlights: 

• Stable low-work function electrodes:  By applying a thin layer of amine-containing polymers to a stable, high-work function material, the group created air-stable, low-work function electrodes. Both types of electrodes must be present for functionality of an organic electrical device, but low-work function electrodes are notoriously environmentally unstable. This process circumvents the need to use air-sensitive materials, essentially creating efficient, economical, organic semiconductor devices.
• Superior OTFTs with dual-layer gate dielectric geometry: OTFTs have superior performance compared to amorphous silicon-based devices, but they are hampered by threshold voltage instability when using a single layer gate dielectric or insulating layer. The group developed a method to produce a two-layer gate geometry. Each layer ages, or degrades, independently but with an opposite overall effect on electrical performance resulting in a stable threshold voltage.
• Thermally activated delayed fluorescence (TADF) molecules: The group developed a light converter using TADF molecules with a photopolymer resin that produces a light spectrum indistinguishable from natural light. 

Leadership

• Dr. Kippelen has more than 32,000 publication citations and has achieved a Google Scholar h-index of 92.
• Knight of the French Order of National Merit, 2023 – present.
• Vice Provost for International Initiatives and Steven A. Denning Chair for Global Engagement, 2021– present.
• Co-President of the Lafayette Institute, a major optoelectronics commercialization initiative based at Georgia Tech-Europe in Metz, France, 2012 – present.
• Director of the Center for Organic Photonics and Electronics, Georgia Institute of Technology, 2011–2019.
• Founding editor of Energy Express and former deputy editor of Optics Express.
• International Society for Optical Engineering (SPIE), Fellow, 2007 – present.
• Optica (formerly optical society of America (OSA), Fellow, 2006 – present. 
• Professor and Joseph M. Pettit Professor (since 2013) of Electrical and Computer Engineering, 2003 – present.