First-principles electronic structure of light-emitting and transport materials: Zinc(II)2-(2-hydroxyphenyl)benzothiazolate

Bis(2-(2-hydroxyphenyl)benzthiazolate)zinc(II), [Zn(BTZ)2]2, is amongst the best white-light emissive as well as electron transport materials used in organic light-emitting diodes (OLEDs). In order to gain a deeper understanding for its carrier transport properties, we adopt the density-functional theory (DFT) with generalized gradient approximation (GGA) to calculate the electronic band structure and the density of states (DOS) by the Becke exchange plus Lee–Yang–Parr correlation (BLYP) functional. The intermolecular interaction related to transport behavior has been analyzed from the bandwidths and band gaps. Within the effective mass approximation, we find that the mobility of electron is about two times larger than that for the hole. Furthermore, if we consider the bands near Fermi level, we conclude that the interband gaps within the unoccupied bands are generally smaller than those for the occupied bands, which indicate that the electron can hop through scattering from one band to another, much easier than the hole. These facts indicate that, in [Zn(BTZ)2]2, the electron are the dominant carriers in transport, in contrast to most organic materials.