Nickel sulphide (NiS) nano-composite were synthesized and used as dopant in the hole transport layer of the thin film organic solar cell (TFOSC). The nano-particles are intended to assist in the charge transport processes at the interface between the active layer and the anode. Thin film solar cells were fabricated using photo-active layer composed of poly-3-hexylthiophene (P3HT) and (6-6) phenyl-C61-butyric acid methyl ester (PCBM) blend. The solar cells employed NiS doped PEDOT:PSS hole transport layer (HTL) which are investigated in terms of changes in optical and electrical properties of the films. The electrical properties of the newly fabricated solar cells showed significant improvement in photo-generated current as the result of reduced charge carrier recombination and enhanced charge transport processes at the interface. This in turn boost the power conversion efficiency (PCE) of the devices by 95% compared to the devices without NiS doped HTL. The observed PCE enhancement is attributable to the excitation of the localized surface plasmon resonance exhibited by the presence of NiS in hole transport layer. It is noted in the investigation that the performance of the solar cell is dependant on the concentration of NiS nano-particles in PEDOT:PSS layer. As consequence, the highest recorded PCE in this study was 6.03% at 0.1% NiS by weight, which is encouraging result for device fabrication in ambient laboratory condition.