Abstract
Hybrid organic-inorganic materials are among the latest class of materials proposed for thermoelectric applications. The organic-inorganic interface is critical in determining the effective transport properties of the hybrid material. We study the thermoelectric properties of the tetrafluoro-tetracyanoquinodimethane (F4TCNQ)–silicon interface. Transfer of electrons from silicon to F4TCNQ results in holes trapped within the screening length of the interface that can move parallel to the interface. We measure the response of these trapped charges to applied temperature differential and compare the thermoelectric transport properties of the silicon with and without F4TCNQ. The results confirm the presence of interface charges and demonstrate an enhanced interface thermoelectric power factor. These outcomes of this study could be used in designing 3D hybrid structures with closely packed interfaces to replicate a bulk thermoelectric material.
Highlights
In this work, we fabricated a device to investigate the charge transfer of the tetrafluoro-tetracyanoquinodimethane (F4TCNQ)–silicon interface
F4TCNQ is a fluorinated TCNQ derivative and has an exceptionally high electron affinity of Ea = 5.24 eV.29. It is well known as a strong electron acceptor, to dope molecules p-type by forming a charge transfer organic complex, as well as to enhance hole injection by energy level alignment at organic–metal interfaces
F4TCNQ has been widely applied in organic light emitting diodes (OLEDs),32,33 photovoltaics,34,35 organic fieldeffect transistors (OFETs),36 etc
Summary
We fabricated a device to investigate the charge transfer of the tetrafluoro-tetracyanoquinodimethane (F4TCNQ)–silicon interface. As the most pervasive semiconductor material for electronic devices, Si has only sparsely been examined experimentally as the active layer for transfer doping by F4TCNQ. This favors electron-transfer from silicon to F4TCNQ molecules, and Si is p-type doped near the interface.
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