Interface Investigation in Organic Solar Cells

Abstract

This thesis work investigates the functional interfaces in organic solar cells (OSCs), since these interfaces are of great importance in controlling the key processes in OSCs such as photon-induced charge carrier generation, transport and extraction. The electronic structure and the molecular orientation of three model systems in inverted OSC structures are carefully examined mainly by ultraviolet photoelectron spectroscopy (UPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. Firstly, the donor-acceptor interface is investigated by employing chloroaluminium phthalocyanine (ClAlPc)/fullerene (C60) heterojunction as a model system. Secondly, CVD graphene modified copper-hexadecafluoro-phthalocyanine (F16CuPc)/copper phthalocyanine (CuPc) heterojunction demonstrates the interfacial layer could effectively engineer the donor-acceptor heterojunction. Thirdly, how poly [(9,9-bis(3?-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9?dioctylfluorene)] (PFN) can act as an efficient cathode interfacial layer is investigated from the view of energy level alignment. In each study, the model device fabrication and characterization provide information to correlate the interface properties with the device performance.