To verify our bottom-up parameterization method, we first applied it to simple systems, including benzene, thiophene, and benzenethiol. After successfully parameterizing the cation-π interactions for these systems, we extended our model to more complex systems, such as the "Free TBT monomer" and the "PTBT constituent monomer". With this bottomup approach, we can parameterize not only the simple organic molecules but also polymer monomers. Additionally, this model seamlessly integrated with the fixed-charge OPLS-AA force field. However, the limitation of the optimized force field is that it might not be fully transferable to all configurations and geometries. As a fixed-charge non-polarizable force field, it is efficient and can be used for upscaling to larger systems. However, as the parameters are based on minimal energy conditions in the gas phase, inaccuracies may occur for dense and highly stressed polymers. For systems close to the benchmark, it is expected that the OPLS-AA/corr. force field will perform better than the uncorrected one.