Array substrate, method for fabricating the same, display panel, and display device

A method for fabricating an array substrate, the method comprising:

• forming an active layer on a substrate;
• forming a gate electrode and a first electrode on the active layer;
• forming a first insulating layer on the gate electrode and the first electrode;
• forming a barrier material layer on the first insulating layer;
• performing one patterning process on the barrier material layer to form a barrier and a second electrode, wherein a projection of the second electrode on the substrate at least partially overlaps a projection of the first electrode on the substrate, and wherein a projection of a portion of the barrier extending outward from a side of the gate electrode on the substrate is within a projection of a portion of the active layer extending outward from a side of the active layer on the substrate;
• and
• performing a first doping on the active layer by using the barrier as a mask to form source/drain regions on both sides of the channel region of the active layer and a lightly doped drain region between the channel region and the source/drain regions.