Efficient Polymer Solar Cells with Vertical Gradient Morphology Achieved by Ternary and Sequential Deposition Strategies

Optimizing the active layer morphology is essential for enhancing charge separation and collection, thereby improving the performance of organic solar cells (PSCs). In this study, we employ a combination of ternary strategy and sequential layer-by-layer deposition strategies to optimize the energy level structure, broaden the visible light absorption, and regulate the vertical phase separation morphology. This approach imparts a vertical gradient phase separation microstructure morphology of the active layer, significantly improving carrier transport and charge collection efficiency, ultimately enhancing the power conversion efficiency (PCE) and stability of the solar cells. As results, the open-circuit voltage (V), short-circuit current density (J), and fill factor (FF) based on D18-Cl/L8-BO:Y6-BO-4F were effectively enhanced, achieving an efficiency of more than 18%. This work demonstrates an effective and straightforward method for fabricating high-performance and stable PSCs, providing valuable insights into future research and development in this field.