Polymer formation in conductive Mg-doped C60 films

Mg-doping in a C60 layer is expected to improve the electrical conduction in organic solar cells. However, the mechanism of conductivity improvement and the detailed structure of Mg-doped C60 material are still unclear. In this study, we investigated the vibrational spectra to understand structural change in Mg-doped C60 in terms of the bonding state of the adjacent C60 molecules. IR spectra can be explained by several types of C60 polymer formation in Mg-doped C60 even with the low Mg concentration. It is thought that the existence of several types of short length C60 polymers cause the crystal quality degradation.