Optical conductivity and optical effective mass in a high-mobility organic semiconductor: Implications for the nature of charge transport

摘要

We present a multiscale modeling of the infrared optical properties of therubrene crystal. The results are in very good agreement with the experimentaldata that point to nonmonotonic features in the optical conductivity spectrumand small optical effective masses. We find that, in the static-disorderapproximation, the nonlocal electron-phonon interactions stemming fromlow-frequency lattice vibrations can decrease the optical effective masses andlead to lighter quasiparticles. On the other hand, the charge-transport andinfrared optical properties of the rubrene crystal at room temperature aredemonstrated to be governed by localized carriers driven by inherent thermaldisorders. Our findings underline that the presence of apparently lightcarriers in high-mobility organic semiconductors does not necessarily implyband-like transport.