Modification of charge transport in single crystal rubrene

To investigate the impact of impurities on properties of single crystals of rubrene (C 48 H 24 ), we consider structural, charge transport and optical properties. We show that transport properties are strongly influenced by the presence of a bandgap acceptor state, commonly occurring in crystals of rubrene. The bandgap state is likely caused by incorporation of an oxygen-related impurity. We demonstrate that the impurity presence can be detected using optical spectroscopy. The impurity model explains commonly-observed variations of rubrene properties. The acceptor-like characteristics of the impurity suggests a possible approach for modification of the charge transport in molecular crystals.