Modulating Charge Transport Kinetics of Bulkheterojunction 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,1 and reduces charge leakage, hence a higher power conversion efficiency (PCE), by functioning as an electron blocking layer (EBL).2 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.3 The inhomogeneous electronic structure of PEDOT:PSS IFL impedes the formation of uniform contacts and charge transport,4 and PEDOT:PSS diffusion into the active layer after device fabrication diminishes the device lifetime.5