Transparent thin-film transistors (TTFTs) with an indium-zinc oxide (IZO) active layer by the solution-processed deposition method were fabricated and their TFT characterization was examined. Solution-processed IZO thin films were amorphous and highly transparent with >90% transmittance in the visible region with an optical bandgap of 3.1 eV. Spin-coated IZO TTFTs were operated in depletion mode and showed a field-effect mobility as high as 7.3 cm(2)/V s, a threshold voltage of 2.5 V, an on/off current ratio greater than 107, and a subthreshold slope of 1.47 V/decade. (C) 2007 The Electrochemical Society.