Heterojunction solar cells based on ternary blends of two donors (absorbers and one acceptor) were investigated using modeling. The Tauc-Lorentz model and experimental absorption spectra of selected compounds were used in the simulations. The optimization process was carried out in this way to maximize the absorption of the system. Poly(3-hexylthiophene-2,5-diyl) (PEHT) was investigated as a first donor, which was mixed respectively with poly(3-octylthiophene-2,5-diyl) (P3OT), coumarin 153, purpurin, fluorescent brightener 184, N-chloroethylene carbazole, and 1,3,6,8 tetrachloro 9n amylocarbazole. Simulations were also performed for the Tauc-Lorentz model.