Six indole based thiazole substituted donor-π-acceptor molecules are designed and their nonlinear optical properties (NLO) are evaluated theoretically. Different electron withdrawing groups and π-linkers are used to understand their role in tuning the NLO properties. The NLO properties of the molecules are analyzed in gas phase and in different solvent medium through the dipole moment, static polarizability, first and second hyperpolarizabilities. Efficiency of the molecules are studied through HOMO-LUMO gap, frontier molecular orbitals, light harvesting efficiency, ionization potential, electron affinity and reorganization energy for hole and electron. All the dyes show maximum absorption wavelength in the visible region. The computed absorption spectra are well correlated with the HOMO-LUMO gaps of the molecules. The HOMO-LUMO gaps of all the dyes are found to be small, which lead to large NLO response. Results indicate that hyperpolarizability increases with increasing strength of the electron withdrawing group. In addition to the study of nonlinear optical property, we also calculate relevant parameters related to photovoltaic cells for two designed dyes which emerge suitable for this purpose. Photovoltaic parameters such as electron injection efficiency, exciton binding energy, and open circuit photovoltage are evaluated for dye sensitized solar cells (DSSC) applications. This study shows that alkyne π-linkers are better than the alkene π-linkers for desired applications. Overall, this study highlights the optical and photovoltaic nature of the dyes and reveals the influence of different πlinkers and electron acceptors in designing new materials for NLO and DSSC applications.[a] T.