In this paper, a-Si:H/a-Si:H tandem solar cells have been fabricated using a plasma enhanced chemical vapor deposition. The solar cell has a structure of glass/textured-SnO2/p-a-SiC:H/i-a-Si:H/n-mu c-Si:H/p-mu c-Si:H/p-a-SiC:H/i-a-Si:H/n-mu c-Si:H/gallium-doped zinc oxide/Ag. Higher efficiency in a-Si:H/a-Si:H tandem solar cells can be achieved by use of a good tunnel recombination junction (TRJ) and current matching. Accordingly, solar cells with a n-mu c-Si:H/p-mu c-Si:H TRJ are investigated. This paper studies the influence of the thickness of the top intrinsic amorphous silicon (i-a-Si:H) layer with regard to short circuit current density and current matching between the top and the bottom cells. Experimental results with lab-fabricated samples show that the optimal thickness of the i-a-Si:H layer in the top and bottom cells is 60 and 250 nm, respectively. An initial conversion efficiency of 10.29% is achieved for the optimized a-Si:H/a-Si:H tandem solar cell. Light-induced degradation of the solar cells is about 17%. (c) 2012 Elsevier B.V. All rights reserved.