Optimizing the film formation of high crystalline donors for efficient organic solar cells

The complex morphology regulation of the active layer of organic solar cells (OSCs) remains crucial for enhancing photovoltaic performance. However, understanding the transformation of solution aggregates to films under microstructure remains a challenging task. Reasonably introducing the third component guest is a simple and effective way to improve the molecular stacking and crystallinity of the active layer thin film. For this purpose, we designed and synthesized two highly crystalline polymer donors, D18-Si and D18-SiCl, and used them as the third component to improve molecular aggregation and induce crystallization. The results indicated that in the device with PM6:Y6 system, the OSC with D18-SiCl as the third component crystallization inducer obtains a power conversion efficiency (PCE) of 17.51%, which is significantly better than the PCE value of 16.03% of the control device. And a remarkable PCE of 18.67% is obtained in the ternary OSC based on the active layer of PM6: D18-SiCl: BTP-eC9. The achievement of excellent efficiency is mainly due to the optimization of film formation time, which prompted to the improvement of film morphology, thereby attributed to its higher exciton dissociation and charge transport. Our work provides a strategy for the in-depth study of the film-forming process of high-efficiency three-component.