An Overview of Electron Transport Layer Materials and Structures for Efficient Organic Photovoltaic Cells

The electron transport layer (ETL) has gained significant attention recently for its essential role in facilitating charge extraction, transportation, and reducing recombination in photovoltaic cells. Organic photovoltaics (OPVs) with ETLs have achieved remarkable efficiencies exceeding 19%, and indoor OPVs have reached a peak efficiency of 29.4% under 3000 LX illumination. Despite these accomplishments, the difficulties in choosing appropriate ETLs for contact alignment have constrained device performance. This review comprehensively overviews the latest advancements in ETL materials used in conventional and inverted OPVs. Additionally, it investigates the evolution of dopant materials, emphasizing the need for improved electron mobility, energy level alignment, and surface passivation treatment of the buffer layer and absorber layers in OPVs. Continual studies of transport materials and the potential utilization of doping or multilayer ETLs are suggested as inevitable research toward achieving higher power conversion efficiency and stability in OPV technology. Additionally, identifying optimal ETL materials capable of synergistic interactions remains crucial for sustained progress in renewable energy technology.