Researchers from Dresden University of Technology revealed that the properties of host–dopant integer charge transfer complexes in efficiently doped organic semiconductors control charge transport
Organic semiconductors allow to fabricate large-scale printed and mechanically flexible electronic applications. These semiconductors are used in displays in the form of organic light-emitting diodes (OLEDs). However, doping is required to further improve organic semiconductors. Doping refers to the targeted introduction of impurities, which are also called as dopants, into the semiconductor material of an integrated circuit. These dopants act as intentional disturbances in the semiconductor and can be used to control the behavior of the charge carriers. This in turn allows to control the electrical conductivity of the original material. Moreover, even small amounts of dopants can have a strong impact on electrical conductivity. Molecular doping plays a major role in several commercial organic electronics applications.
However, lack of fundamental physical understanding of the transport mechanisms of charges in doped organic semiconductors has restricted a further increase in conductivity. Now, a team of researchers from the Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and the Center for Advancing Electronics Dresden (CFAED) at Dresden University of Technology identified key parameters that impact electrical conductivity in doped organic conductors. The team conducted experimental investigations and simulations to demonstrate that complexes of two oppositely charged molecules are generated when dopant molecules are introduced into organic semiconductors.
The properties and density of these complexes determine the energy barriers for the transport of charge carriers, which in turn determines the level of electrical conductivity. According to the researchers, the ability to identify important molecular parameters offers an important foundation for the development of new materials with even higher conductivity. The research was conducted in collaboration with Stanford University and the Institute for Molecular Science in Okazaki and published in the journal Nature Materials on January 28, 2019.
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