Leveraging Multilayer Hole Selective Layers to Boost Organic Photovoltaic Power Conversion Efficiency

Hole selective layers (HSLs) play a crucial role in the efficiency of organic photovoltaics (OPVs). Self-assembled monolayers (SAMs) offer a powerful approach to engineer the interfacial properties of HSLs in OPVs. In this work, we utilized the 2-(9H-carbazol-9-yl)ethyl)phosphonic acid (2PACz) SAM to modify the ITO/MoO3 interface and the surface of MoO3, thereby forming multilayer HSLs. 2PACz regulates the surface work function (WF) of the electrodes, leading to a more favorable energy level alignment, reduced interfacial resistance, and facilitated charge carrier transport and extraction. The resulting OPV devices demonstrated improved fill factor (FF) and power conversion efficiency (PCE). Additionally, the reduction in interface defects effectively suppressed carrier recombination, ultimately achieving a maximum PCE of 16.33%. This indicates that the design of composite HSLs with multilayer interface modification is an effective strategy for improving OPV efficiency and provides ideas for further advancing OPV development.