A polymer design strategy toward green solvent processed efficient non-fullerene polymer solar cells

So far, the most successful and widely used solvents in polymer solar cells (PSCs) are chlorinated solvents like chloroform (CF), 1,2-dichlorobenzene (DCB) and chlorobenzene (CB), which are highly detrimental to human health and the environment. In this work, by the approach of manipulating flexible and conjugated side groups of a widely used polymer donor material (PBDB-T), two new polymers named PBDB-T-BO and PBDB-BzT are designed and synthesized to improve the solubility and fine-tune the aggregation property in tetrahydrofuran (THF), a much more benign solvent. As a result, an outstanding PCE of 12.10% was achieved with the THF-processed PBDB-BzT: IT-M device. The result in this work demonstrates the importance to modulate the aggregation effect of the polymer in solution by inserting conjugated groups and also suggests a feasible method to convert the main processing solvent of a highly efficient non-fullerene (NF)-PSC from CB into THF.