In this paper we report the effect of scattering and plasmon enhancement on the energy conversion efficiency of silver nanoparticles (nps) incorporated azo/si heterojunction solar cells. The studied solar cell structure consists of a 240 nm of heavily al doped zno (azo) layer with ag nps on an n-type si. Therefore, azo layer is considered as a transparent current spreading layer with enhanced conductivity as well as rectifying junction with a si. Computer simulation using fdtd method was carried out to explore the effect of ag nps at different positions, densities and sizes in an azo layer. Also, the results were compared to the fabricated devices. To analyze the scattering and plasmon resonance effect, the energy distribution and current generation from azo to si layer was calculated in a spectral range of 400 nm to 1100 nm using standard solar spectrum with 100 mw/cm2 of power density. The calculations were performed, introducing three variables, which are 10-150 nm of nanoparticles sizes, 5-45 % of surface loading amount, and 0-100 nm of nanoparticle position from the junction. This study reveals that there is a certain position (20-40 nm from the azo/si junction) of nanoparticles inside the structure where the energy conversion efficiency reaches to its maximum. These results were well matched with the fabricated solar cells using same structures. The best performance of azo /si heterojunction solar cell was shown to have 0.36 v of Voc, 28.3 ma/cm2 of jsc and an efficiency of 5.91 % when the ag np layer were located at 30 nm from the junction. This study will benefit to the design of surface plasmon enhanced solar cell structure using metallic nanoparticles to maximize the surface plasmon effect and to minimize scattering losses.