Embodiments of the disclosure provide a thin-film transistor, an array substrate, a display panel and a display device. The thin-film transistor includes a current enhancement portion, and the current enhancement portion is provided between a drain and a source. The current enhancement portion may include at least one protrusion portion, and the protrusion portion is provided on the drain and/or the source and faces a channel. The current enhancement portion may include an island portion provided between the drain and the source, and the island portion is separate from the drain and the source. The island portion may include at least one protrusion end, and the at least one protrusion end faces the drain and/or the source.