Evaluating intrinsic mobility from transient terahertz conductivity spectra of microcrystal samples of organic molecular semiconductors

Abstract

In microcrystal samples of the prototypical organic molecular semiconductors rubrene and C10-DNTT (2,9-didecyl-dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene), we measured spectra of complex optical conductivity caused by photocarriers with optical-pump terahertz-probe spectroscopy. We analyzed the σ - ω spectra using the Drude-Smith model and evaluated the DC mobility μ DC, which includes extrinsic effects, and the intrinsic mobility μ int. The resulting μ DC and μ int values are comparable to the mobility values obtained using transport measurements of polycrystalline and single-crystalline field-effect transistors, respectively. This correspondence demonstrates that the intrinsic mobility values of organic molecular semiconductors can be evaluated from the measurements of microcrystal samples using transient terahertz spectroscopy.