Enhancing efficiency and stability of ternary polymer solar cells by employing donor dilution and layer-by-layer fabrication techniques

Optimizing the morphology of the active layer is crucial for enhancing the power conversion efficiency (PCE) of polymer solar cells (PSCs), a key objective in organic photovoltaic research. In this study, we achieved significant improvements in active layer morphology by employing a synergistic combination of the sequential deposition method and the donor dilution strategy. In addition, a small amount of molecular acceptor was introduced as a third component into the donor layer, it was proved that the third component facilitated downward penetration of the upper layer of acceptor materials and establishing a gradient distribution of the donor-acceptor interface along the vertical direction, which enhanced both the utilization and transport efficiency of charge carriers. Moreover, the presence of the third component partially suppressed the formation of pure donor phases, further enhancing exciton dissociation and increasing charge collection efficiency. As a result, the short-circuit current density (J_sc), fill factor (FF), and open-circuit voltage (V_oc) of the PBQx-TF: L8-BO/BTP-eC9-based PSCs were significantly improved, and ultimately resulting in PCEs surpassding 18 %. Therefore, this work presents a valuable strategy for fabricating high-performance PSCs, offering insights into optimizing active layer morphology for improved photovoltaic performance.