FET-based charge carrier mobility measurements in low-conductivity materials, as well as semiconductor materials with a high density of trapping states, such as nanocrystals and polycrystalline films, are highly distorted due to charge accumulation in the transistor structure. In this work, a comparative study of the measurement of the mobility of charge carrier in conductive polymers, nanocrystals and polycrystalline films, using the analysis of output and transfer characteristics, was carried out. It is shown that using output characteristics instead of transfer characteristics for calculating the charge carrier mobility helps to avoid a systematic error in the measurement.