A thin film transistor, an array substrate and a display device are disclosed, the thin film transistor comprises a gate electrode, an active layer located on the gate electrode, and a source electrode and a drain electrode respectively located at opposite sides of the active layer and both partially overlapped with the active layer; the active layer includes at least one first structure part and at least one second structure part, a material for the first structure part is semiconductor, and a material for the second structure part is predetermined conductor, and the predetermined conductor has better conductivity than the conductivity of the conducted semiconductor, and in response to that a turn-on voltage is applied to the gate electrode, a conductive passage located between the source electrode and the drain electrode includes the first structure part and the second structure part.