Rapidly Measuring Charge Carrier Mobility of Organic Semiconductor Films Upon a Point-Contact Four-Probes Method

Abstract

Field-effect mobility ( ${\mu }_{\mathrm{ FET}}$ ) of organic semiconductor films plays a key role in the performance of field-effect transistors (FETs). Numerical extraction of ${\mu }_{\mathrm{ FET}}$ from organic FET characteristics is not only time-consuming due to patterning of source/drain electrodes, but also frequently unreliable because of the contact resistances ( ${R} _{\mathrm{ C}}$ ) between source/drain electrodes and semiconductors. Here, we propose an approach to rapidly evaluate ${\mu }$ by a point-contact four-probes method ( $\mu _{\mathrm{ PFP}}$ ) for organic semiconductor films. Four tip-like probes quickly contact the semiconductor film surface directly, without deposition of the conventional source/drain electrodes, to simultaneously inject current and measure the electric potential. The charge density and thus conductance of the film is manipulated upon scanning gate voltage, from which the extraction of ${\mu } _{\mathrm{ PFP}}$ , in good agreement with ${\mu }_{\mathrm{ FET}}$ , could be realized in a few seconds. This method, with easily accessible setup and numerical model, substantially accelerates the evaluation of ${\mu }_{\mathrm{ PFP}}$ , and thus could help screen materials and optimize film morphology for organic FETs applications.