In this work, the effect of gold (Au) nanoparticles on the performance of a-Si:H solar cells is investigated experimentally. The solar cell stack is grown on a highly doped p-type Si wafer and consists of 20 nm heavily doped p-type a-Si, 500 nm undoped a-Si, 20 nm heavily doped n-type a-Si and finally 80 urn Indium Tin Oxide (ITO) on the top. Au nanoparticles of 10, 20, 50, 80, 100, 200 and 400 nm are spin coated on top of the ITO before metallization. The plasmonic effect of the Au nanoparticles allows for additional scattering at the surface thus reducing the overall reflectivity. The larger the nanoparticle size the more scattering is obtained and the median reflectivity drops from about 23% to 18%. The results show an increase in the short-circuit current density (J(sc)) and efficiency with increasing nanoparticle size. The J(sc) increases from 9.34 to 10.1 mA/cm(2). In addition, the efficiency increases from 4.28% to 5.01%. (C) 2014 Elsevier Ltd. All rights reserved.