Functional Self-Assembled Monolayers for Large Photoinduced Charge Transfer in Organic Field-Effect Transistors

摘要

Here we describe a structure designed to optimize photoinduced charge transfer in thin film devices. Bulk composite structures produce large effects in optical spectroscopy, in which photoluminescence is quenched by rapid charge transfer to an electron acceptor. Thin films exhibiting photoinduced transfer have traditionally been envisioned for photovoltaic devices using bulk mixtures of semiconductors and molecules with electron acceptors.,3 Bulk composite photoinduced charge transfer materials produce a much smaller effect in field-effect transistor (FET) structures than photovoltaics. In FETs, because only a nanometer-scale thickness of material contributes to charge transport, the effect of a bulk composite is limited. Intramolecular charge transfer in a bifunctional spiro compound in a FET configuration, for example, have shown a shift in the FET threshold voltage VT shift of only 20 to 30 V. In addition, the electrostatic complexity of bulk composites makes accurate measurements of the induced charge densities difficult. We can get a clearer view of photoinduced charge transfer mechanisms by designing controlled interfaces.