Thin-film silicon solar cells are potential for cost-effective photovoltaics, but their application is significantly limited due to poor optical absorption and limited photogeneration rates at sub-micron active layers. To overcome this, advanced light-harvesting techniques are being studied, plasmonic light trapping via metal nanostructures has emerged as a promising technique to improve the optical absorption and carrier generation via coupling the incident spectrum into localized surface plasmon resonances (LSPR). This phenomenon enhances the induced electromagnetic filed at the metal-semiconductor interface, leads to improved photon trapping in the absorber layer and overall photocurrent. The tuneability of plasmonic behaviour, through parametric optimization of nanoparticle diameter, shape, periodic distribution, and dielectric environment, provides a very essential degree of freedom for optimizing the overall performance of the solar cells. In this study, silver coated polystyrene (AgPs) core-shell metal nanoparticles are incorporated into a sub-micron crystalline silicon absorber layer, where their plasmonic properties ensures effective light trapping while maintaining reduced absorber layer thickness. By systematically tuning the nanoparticles size, orientation, periodic density, and their placement within the absorber layer, we have optimized the optoelectronic performance of the proposed design. In comparison to an untextured, ARC-free planar silicon solar cell, the proposed design has achieved 43.30% much higher PCE with an excellent short-circuit current density (jSCPrac) of 29.95 mA/cm2, an open circuit voltage (Voc) of 0.61 V, and Fill factor (FF) of 82.16%, under AM 1.5G solar illumination. These findings highlight the effectiveness of plasmon engineered nanostructures for overcoming optical losses in sub-micron absorber layers, and also offers a scalable and material-efficient strategy for future next-generation solar cells.