Controllable ZnMgO Electron-Transporting Layers for Long-Term Stable Organic Solar Cells with 8.06% Efficiency after One-Year Storage

Currently, one main challenge in organic solar cells (OSCs) is to achieve both good stability and high power conversion efficiencies (PCEs). Here, highly efficient and long-term stable inverted OSCs are fabricated by combining controllable ZnMgO (ZMO) cathode interfacial materials with a polymer:fullerene bulk-heterojunction. The resulting devices based on the nanocolloid/nanoridge ZMO electron-transporting layers (ETLs) show greatly enhanced performance compared to that of the conventional devices or control devices without ZMO or with ZnO ETLs. The ZMO-based OSCs maintain 84%-93% of their original PCEs over 1-year storage under ambient conditions. An initial PCE of 9.39% is achieved for the best device, and it still retains a high PCE of 8.06% after 1-year storage, which represents a record high value for long-term stable OSCs. The excellent performance is attributed to the enhanced electron transportation/collection, reduced interfacial energy losses, and improved stability of the nanocolloid ZMO ETL. These findings provide a promising way to develop OSCs with high efficiencies and long device lifetime towards practical applications.