Modulating Charge Transport Kinetics of Bulk-heterojunction Organic Photovoltaics via the Addition of Dipolar Monolayer at the Electrode Surface

摘要

Insertion of an interfacial layer (IFL) between the active layer and anode in bulk-heterojunction (BHJ) organic photovoltaics (OPVs) plays a vital role in enhancing device performance. The IFL improves physical adhesion of the active layer to the anode, hence thermal durability, and reduces charge leakage, hence a higher power conversion efficiency (PCE), by functioning as an electron blocking layer (EBL). The dominant IFL material currently used in conventional OPV device fabrication is PEDOT:PSS. However, there are innate undesirable features of its surface properties. The corrosive sulfonic acid moieties of PEDOT:PSS shorten device lifetime by etching the electrode and decomposing active layer materials. The inhomogeneous electronic structure of PEDOT:PSS IFL impedes the formation of uniform contacts and charge transport, and PEDOT:PSS diffusion into the active layer after device fabrication diminishes the device lifetime.