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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.
Fig. 1