We report a development of a highly transparent conductive film (TCF) which is the first embedded metal grid of fine lines on a flexible substrate. The TCF reveals excellent electrical and optical performance as transparent conductive film with an extremely high sigma(DC)/sigma(OP) value of 237 due to 80.35% transmittance and 6.85 Omega/square sheet resistance. Furthermore, the extremely high performance is realized with new features of the TCFs: roll-to-roll printability on flexible substrates,' thermal imprinting of channels at 10 mu m widths, water-based nano-silver paste to fill the narrow channels, and doctor blade as a facile method to fill the paste into the channels. The TCF electrode is implemented to fabrication of an organic solar cell (OSC) which shows a power conversion efficiency of 1.40%. This is non-optimized yet but approaching that of an ITO-based OSC (1.70%). Thus, we demonstrate a printable TCF to replace the ITO films toward low-cost large area roll-to-roll fabrication of organic solar cells. (C) 2012 Elsevier B.V. All rights reserved.