Simultaneous improvement of three parameters using a binary processing solvent system approach in as-cast non-fullerene solar cells

Abstract

As-cast polymer solar cells without any additive and pre- or post-treatments principally have high compatibility with mass production technologies, and efforts in achieving higher efficiencies are typically promoted by engineering new donor and acceptor materials. In this study, a binary solvent processing approach using chloroform (CF), as a good low boiling point solvent for both the donor polymer PTQ10 and the non-fullerene acceptor IT-4Cl, and mesitylene (MES), as a semi-orthogonal co-solvent with relatively high boiling point and weak solubility to the acceptor, is explored. Due to the selective orthogonality of MES to the IT-4Cl acceptor, an optimized morphology has been realized for the as-cast device based on the PTQ10:IT-4Cl blend, which leads to a simultaneous improvement in the open-circuit voltage, short-circuit current, and fill factor, finally achieving a high as-cast efficiency of over 13%. Furthermore, the as-cast devices fabricated with this binary solvent system exhibit good air stability and great accessibility in large area cells. Our findings provide an alternative guideline for the optimization of as-cast polymer solar cells.