Poly (3-hexylthiophene) (P3HT) and modified (functionalized and silanized) multi wall carbon nanotube (MWNT) nanocomposites have been prepared through in-situ polymerization process in chloroform medium with FeCl3 oxidant at room temperature. The composites (P3HT-MWNT) are characterized through Fourier transfer infrared spectroscopy (FT-IR), Raman and X-ray diffraction (XRD) measurements to probe the nature of interaction between the moieties. Optical properties of the composites are measured from ultraviolet-visible (UV-Vis) and photoluminescence (PL) spectroscopy. Conductivity of the composites is followed by four probe technique to understand the conduction mechanism. The change (if any) in C=C symmetric and antisymmetric stretching frequencies in FT-IR, the shift in G band frequencies in Raman, any alterations in max of UV-Vis and PL spectroscopic measurements are monitored with modified MWNT loading in the polymer matrix. Finally, a quasi solid-state dye synthesized solar cells (DSC) with the hybrid P3HT-MWNT composites, an ionic liquid of 1-methyl-3-propyl imidazolium iodide (PMII) are placed between the dye-sensitized porous TiO2 and the Pt counter electrode without adding of iodine and achieved higher cell efficiency (4.1%), as compared to that containing bare PMII (0.29%. The P3HT-MWNT nanoparticles exploits as the extended electron transfer materials and serve simultaneously as a catalyst for the electrochemical reduction of I3−.