Pulsed DC magnetron sputtering was used to deposit indium tin-oxide (ITO) thin films on glass substrates for application in photovoltaic devices as the final window layer. The evolution of crystal phase, morphology, resistivity and transmittance of the ITO films under different thermal annealing procedure (in-situ annealing versus post-annealing) at relatively low temperatures (up to 300 degrees C) were studied. Fully crystalline ITO films with low sheet resistance of 24 Omega/square and high average transmittance (exclude glass substrate) of 90.10% with a Haacke's figure of merit 1.47 x 10(-2) Omega(-1) were obtained by in-situ annealing at 200 degrees C. In comparison, theminimumtemperature observed to fully crystalize the ITO thin films with competitive crystallinity, electrical and optical properties by post-annealing was 250 degrees C. The corresponding post-annealed 300 nm thick films showed sheet resistance of 49 Omega/square and average transmittance (exclude glass substrate) as high as 91.93% with a Haacke's figure of merit 0.882 x 10(-2) Omega(-1). The surface morphology of the as-deposited ITO films remained homogeneous after post-annealing whereas large particles (up to 100 nm) were observed on the surface of the films deposited by in-situ annealing. The results indicated that different thermal treatment procedures at lower temperatures produce significant effect on the electrical, optical and other physical properties of the ITO thin films which are critical for the window layer in photovoltaics. (C) 2017 Elsevier B.V. All rights reserved.