Plasticized solid polymeric electrolyte nanocomposites based on polyvinyl alcohol (PVA) incorporating Cs2CuO2 nanoparticles (NPs), electrolyte salt (LiClO4) and plasticizer (PC) were prepared via solution casting technique. The dynamic light-scattering histogram revealed that the prepared Cs2CuO2 NPs have a size in the range of 80-120 nm. The interaction between different components in PVA/Cs2CuO2/LiClO4-PC films (plasticized PVA-SPEs) were probed by FTIR, while the surface and structure were evaluated by SEM and XRD, which indicate to amorphous nature of plasticized PVA-SPEs. The thermal behavior of films was measured via TGA, where a partial decrease in the thermal stability of films was noticed with an increase of PC content in the PVA-SPEs. The highest conductivity achieved is 9.56X10-5 S/cm for PVA-SPEs containing 8wt% PC at 298K. The plasticized PVA-SPEs exhibited higher specific capacitance by two folds and photovoltaic efficiency by three folds compared to pure PVA matrix.