Unique assembly of giant star-shaped trimer enables non-halogen solvent-fabricated, thermal stable, and efficient organic solar cells

Herein, we report a star-shaped giant trimer (G-Trimer) to fabricate organic solar cells by o-xylene with over 19% efficiency, long-term stability, and accessible up-scaling property, a more potential candidate for commercial photovoltaic materials than its linear-shaped dimer and polymer counterparts. Due to the high molecular weight and unique star-shaped architecture, G-Trimer exhibits a temperature-dependent aggregation property in an o-xylene solvent, and it could also relax disordered entanglements of pre-aggregated PM6 in the PM6/G-Trimer blend solution, promoting a low energetic disorder fibrous morphology in the active layer. This results in a long charge lifetime with efficient dual hole-transfer channels under low driving force, enabling record efficiencies from small to large areas. A small kinetically trapped morphology with high Tg gives the device a T90 of longer than 4,500 h after continuous heating at 80°C without further decay. Our results provide important guidance for developing high-performance photovoltaic materials for their commercialization.