Electrical Properties of Mg Doped C60 Thin Films

C(60) solids have been known as high resistive semiconductor materials. Such high resistivity is one of the reasons of low charge transport efficiency in organic solar cells. Mg doping in C(60) films was done by the co-evaporation method of C(60) and Mg sources. The conductivity could be controlled by the composition ratio of Mg/Cr(60), and its dependence is divided into 3 ranges (Mg/C(60) = 0 similar to 2, 2 similar to 6, >6). Temperature dependence of the conductivity shows hopping conduction mechanism, and suggesting the same hopping center origin in the first and second ranges. From Raman scattering spectroscopy and XRD measurements, the crystal structure disordering by Mg-doping was observed. It is thought that Mg composition dependence of the conductivity is related to both of the conduction mechanism change and the structural change.