Optimizing the solvent and blend morphology results in an additive-free organic photovoltaic achieving 17.8% efficiency

Abstract

The choice of solvent affects the morphology of the active layer blend in organic photovoltaics (OPVs), as well as the device performance and potential commercial applications. In this study we applied two different solvents, chloroform (CF) and chlorobenzene (CB), with optimal process parameters to prepare OPVs based on PM6:BTP-eC9 as the active layer. We used atomic force microscopy and grazing-incidence wide-angle X-ray scattering to evaluate the blend morphologies of the OPVs, and also examined the optoelectronic properties of the blend films and devices. We obtained power conversion efficiencies of up to 17.82% when using CB as the solvent, without any additives. Compared with the device prepared using CF, the optimized CB-derived OPV exhibited a more suitable phase-segregated domain size with stronger face-on molecular stacking, leading to more efficient carrier transport. Thus, optimizing the fabrication conditions and selecting a suitable solvent to optimize the structure of the PM6:BTP-eC9 blend both contributed to the improvement in the performance of the OPV.