A Mixed-Ligand Strategy to Modulate P3HT Regioregularity for High-Efficiency Solar Cells

Sustainable synthesis of polythiophenes (e.g., P3HT) is highly desired for the development of low-cost organic solar cells. Regulating the regioregularity of P3HT is a promising way to boost its performance. Yet, few eco-friendly methods can prepare P3HT with tunable regioregularity. Herein, we put forward a facile strategy to finely modulate the regioregularity of P3HT from 90% to 98% by tuning the molar ratio of two ligands in direct arylation polycondensation. Moreover, the ligand effect on regioregularity is well elucidated with DFT calculations, and the regioregularity effect of P3HT in non-fullerene solar cells is clarified for the first time. Our calorimetric, microscopic, and scattering results show that regioregularity strongly impacts the polymer crystallinity and phase separation, and device performance of the blend films. The P3HT batch with a regioregularity of 95% yields an unprecedented power conversion efficiency of 10.82%. Importantly, this realization firmly provides optimism for cheap materials such as polythiophenes, which are made via eco-friendly polycondensation for the application of solar cells and beyond.