An improved analysis of the low frequency noise in polycrystalline silicon thin-film transistors (polysilicon TFTs) is presented. The analysis takes into account an exponential energy distribution for the density of states and the flat-band voltage fluctuations for the origin of the drain current noise. Analysis of the drain current spectral density enables the characterization of the gate oxide/polysilicon interface and the active polysilicon layer quality. (C) 2004 Elsevier Ltd. All rights reserved.