Organic Electronics
Organic Electronics
Organic Interfaces
Exploring, understanding and controlling organic interfaces have proven to be a rather complex challenge. Interfacial behavior depends not only on the active materials but also on process ability, molecular alignment, grain boundaries or chemisorption and physisorption interactions. Dominating interfacial phenomena is particularly crucial towards the development and improvement of applications such as organic light-emitting devices (OLEDs), photovoltaic cells or organic field-effect transistors (OFETs).
Continuous efforts have been put in developing new materials and manipulating their bulk properties. In fact, the investigation of material systems in which new electronic phenomena arise from the interactions of molecules, is an active topic of research. But interfacial behavior can be radically different from intrinsic properties of the constituent materials.
This principle was used in a TTF/TCNQ system. Taken individually TTF and TCNQ crystals are essentially insulators. But when a TTF and a TCNQ crystal are combined, a two-dimensional interface between the two compounds is established and charge transfer can also occur, leading to a metallic state (Fig. 1). This represents the first example of a new class of fully organic two-dimensional electronic systems, a feat that opens a broad road to future developments.
Smart Textiles
Another topic or research in organic electronics is smart textiles, in particular, integrating electronic functions directly into fibres instead of mounting off-the-shelf electronic components onto the fabrics. Such flexible, almost imperceptible devices will allow us, for instance, to noninvasively monitor physiological and biomechanical signals, like temperature, heart rate and respiration, with applications in healthcare, military and sports. This can open way to more non-conventional applications such as energy-harvesting or e-skin.
Organic and molecular materials combine unusual electronic properties with the possibility of using different processing techniques, namely large-area solution-based methods. In this sense this particular class of materials to be explored as active components for different types of electronic devices to be built directly on textile fibres
All electronic devices need wiring, so to address this issue we have development a pioneering method of to prepare conducting textile fibres using graphene,[ref?] a single layer of carbon atoms with high conductivity and optical transparency, mechanically strong and chemically stable. This seminal result paves way for the emerging field of fibretronics.
This work is a collaboration with the Centre for Graphene Science of the University of Exeter. For more information contact Ana Neves.
Electronics
The use of organic materials on modern electronics has a tremendous interest, particularly in low cost and flexible applications. In order to improve and expand their use in devices like field effect transistors (OFET) and to implement new technologies, not only new materials and manufacturing processing have to be developed, but also a fundamental understanding of the properties of organic interfaces. Organic interfaces formation process is rather complex and no reliable interface-design criteria are available yet.
The main research interest is in developing and using different classes of organic materials in nano-electronic devices to push further our fundamental understanding of their electronic properties, to discover new physical phenomena, and to contribute to the development of new practical electronic applications. The work includes device nano-fabrication integrating new materials, developing new technological processes and physical characterization. Establishing a relationship between molecular organization and physical properties is fundamental towards nano-engineering devices. This is a multidisciplinary field, where complementary knowledge’s are necessary and combined efforts from chemists, physics, material scientist and engineers can truly make a difference and people with different background are welcome and necessary.
For more information on this topic, contact Helena Alves.
Field Effect Transistors
Organic semiconductors show both p- or n-channel or ambipolar conduction depending on their chemical composition. The narrow bandwidth of organic semiconductors makes charge carriers in these materials far more sensitive to their environment than in conventional inorganic semiconductors, particular in n-type materials. Small conjugated molecules, such as the acene family, applied in OFETs have demonstrated that these materials achieve higher mobility when presenting high degree of structural ordering, like in single crystals. This should result in a better device performance and, in addition, it also allows the study of intrinsic electronic properties. The focus of this research has been in using new materials in single-crystal OFET.
This approach has enabled very stimulating results, which have pushed forward some fundamental problems of organic materials. Such an example is the use of a new molecular compound based on a perylene derivative in a single-crystal OFET that achieved very high electron mobility, with excellent FET characteristics in air (Fig.1).
Another example is air-gap FETs with tetramethyltetraselenafulvalene, which were built in and used to demonstrate the occurrence of intrinsic transport. This is the second organic material presenting intrinsic transport and the best at lower temperatures (40K) (Fig 2).