Structural properties of the solidified-Al/regrown-Si structures of screen-printed aluminum contacts on a crystalline silicon solar cell have been studied by transmission electron microscopy (TEM). TEM results revealed that the solidified-Al/regrown-Si boundary is sharply defined except for the local silicon protrusion. A possible mechanism for forming the Si protrusion has been discussed. The results presented in this study suggested that the back-surface field (BSF) layer is the result of the regrown silicon, and the amount of the dissolved Si upon firing is responsible for the BSF thickness. (c) 2008 Elsevier B.V. All rights reserved.