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

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 $σ̃ω$ spectra using the Drude-Smith model and evaluated the DC mobility $μDC$⁠, which includes extrinsic effects, and the intrinsic mobility $μint$⁠. The resulting $μDC$ and $μint$ 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.