In this work we have grown CdS thin films using an ammonia-free chemical bath deposition process for the active layer in thin film transistors. The CdS films were deposited substituting sodium citrate for ammonia as the complexing agent. The electrical characterization of the as-deposited CdS-based thin film transistors shows that the field effect mobility and threshold voltage were in the range of 0.12-0.16 cm(2)V(-1)s(-1) and 8.8-25 V. respectively, depending on the channel length. The device performance was improved considerably after thermal annealing in forming gas at 250 degrees C for 1 h. The mobility of the annealed devices increased to 4.8-8.8 cm(2)V(-1) s the threshold voltage decreased to 8.4-12 V. I(on)/I(off) for the annealed devices was approximately 10(5)-10(6). (C) 2010 Elsevier B.V. All rights reserved.