This research uses computational simulations using SIESTA (Spanish Initiative for Electronic Simulations with Thousands of Atoms) package based on Density Functional Theory (DFT) to explore the free energies, interaction energies, relative stability, stability of bonds, and charges transfer abilities of Organic Photovoltaic (OPV) systems comprising of bis[methano- fullerene (6,6)-phenyl-C61-butyric acid methyl ester] (bisPCBM) as the acceptor and eight different donor polymers. The novel donor polymers are computationally designed based on poly[4,8-bis-substituted-benzo [1,2-b:4,5-b’]dithiophene-2,6-diyl-alt-4-substituted-thieno[3, 4-b]thiophene-2,6-diyl] (PBDTTT) polymer, the main structural changes being the incorporation of Se and F atoms. From the results, it was clear that PCBM makes a wiser choice as the donor compared to bisPCBM for computer simulations. The influence of F atoms was observed in the stability of the system both energetically and structurally. The incorporation of Se negatively affects the feasibility of acceptor-donor interaction.