The role of Y6 as the third component in fullerene-free ternary organic photovoltaics

Abstract The recent use of non-fullerene materials has significantly increased the efficiency of organic photovoltaic (OPV), with ternary OPVs providing an effective means of further enhancing the performance. In this study, we evaluated the role played by the small molecule Y6 as the third component in additive-free PM6 (polymer): Y6:IT-4F (small molecule) ternary OPVs. We used UV–Vis spectroscopy, photoluminescence spectroscopy, and tapping-mode atomic force microscopy to study the effects of various blend ratios on the optoelectronic properties of these OPVs. At the optimized PM6:Y6:IT-4F blend ratio (1:0.35:0.75), we observed the presence of Y6:IT-4F intermediates that efficiently suppressed the over-segregation of Y6 and increased the degree of carrier transport. The optimized ternary OPV delivered an average power conversion efficiency (PCE) of 13.6 ± 0.29% and the best PCE of 14.14%, which was 23% enhancement compared with the binary OPV. The findings suggest that dual effects, caused by the use of solvent and optimization of the blending ratio of primary and secondary acceptors, significantly influence the performance of OPVs.