Previous works on the study of the state creation under gate-bias stress in polysilicon thin film transistors (TFTs) are extended here by some measurements of the transfer characteristics in the temperature range from 90 to 400 K. Using two different qualities of the active layer polysilicon material, the analysis gives evidence of this state creation. Moreover, and surprisingly, the measurements show a nearly constant on-current at temperature lower than 300 K. So, the field effect mobility is nearly constant from 300 to 90 K and, due to the decrease of the off-current, the I-on/I-off ratio increases from 10(7) at 300 K to 10(9) at 90 K. The density of states (DOS) is calculated assuming polycrystalline silicon as a spatially homogeneous material with a uniform distribution of the DOS in the bulk. Using the transconductance of the TFTs at different temperatures, we can check a wide region of the band-gap. The calculation gives a nearly constant DOS in a large part of the gap and very low extended band-tails. A bump, more important with the lower quality material, appears in the DOS after negative gate bias stress.