High performance ternary organic solar cells assisted by red fluorescent materials through improved emission lifetime and complementary short wavelength light absorption†

Abstract

The energy transfer from a third component material to donor materials and the broadening of the absorption spectrum of the photoactive layer both play an important role in the exciton dissociation process and enhancing photon utilization. Suppressing the charge recombination process and enhancing charge carrier transport are promising strategies to improve the photovoltaic performance of organic solar cells (OSCs). In this manuscript, an effective method is presented using the red fluorescence material 4-(dicyanomethylene)-2-tert-butyl-6-(1,1,7,7-tetramethyljulolidin-4-yl-vinyl)-4H-pyran (DCJTB) as the third component and PM6:Y6 as the host photoactive layer. The photoluminescence spectrum of DCJTB is fully covered by the absorption spectrum of PM6, indicating that the energy from DCJTB can transfer to PM6, which prolongs the exciton lifetime and ensures sufficient time for diffusion and dissociation. The efficient short wavelength light absorption capability of DCJTB is beneficial to enhance the photon utilization efficiency. In addition, a small amount of DCJTB as a third component material can improve the crystallinity of a film and provide more efficient charge transport channels. These results suggest that the ternary strategy with the red fluorescence material DCJTB as the third component provides a new design idea to realize high-performance OSCs.