Theoretical and experimental investigation on the influence of the molecular polarizability of novel zinc phthalocyanine derivatives on the open circuit voltage of organic hetero-junction solar cells

The influence of the molecular polarizability α of different donor molecules on the open circuit voltage V oc of organic hetero-junction solar cells (HJCs) was theoretically and experimentally investigated. Therefore, novel zinc phthalocyanine (ZnPc) derivatives were synthesized having phenyl, naphthyl or anthracenyl groups attached to basic ZnPc cores. By adding bulky groups, the molecular polarizability was successively increased. Since the influence of α on the Coulomb interaction of charges will depend on the molecular arrangement of the respective molecules, the respective single crystal structures were solved by high resolution XRD. Based on the solved structures, quantum mechanical calculations of the charge separation mechanism were performed on model systems. The implications of the observed electronic effects will be discussed and related to the device performance.