We have demonstrated ink-jet printed indium tin oxide (ITO) electrode for cost-efficient organic solar cells (OSCs). By ink-jetting of crystalline ITO nano-particles and performing a rapid thermal anneal at 450 degrees C, we were able to obtain directly patterned-ITO electrodes with an average transmittance of 84.14% and a sheet resistance of 202.7 Omega/square without using a conventional photolithography process. The OSCs fabricated on the directly patterned ITO electrodes by ink-jet printing showed an open circuit voltage of 0.57 V. short circuit current of 8.47 mA/cm(2), fill factor of 44%, and power conversion efficiency of 2.13%. This indicates that the ITO directly patterned by ink-jet printing is a viable alternative to sputter-grown ITO electrodes for cost-efficient printing of OSCs due to the absence of a photolithography process for patterning and more efficient ITO material usage. Crown Copyright (C) 2010 Published by Elsevier B.V. All rights reserved.