Display panel, array substrate, and fabrication method thereof

A display panel, comprising:

• a counter substrate;
• and
• an array substrate, comprising:
• a first substrate;
• and
• a plurality of first thin film transistors and a plurality of second thin film transistors on the first substrate, wherein:
• each of the plurality of first thin film transistors includes a first oxide semiconductor layer formed over a first gate electrode, and a first etch stop layer and a second etch stop layer together formed over the first oxide semiconductor layer, wherein the first etch stop layer partially covers the first oxide semiconductor layer, the second etch stop layer encapsulates the first etch stop layer and partially covers the first oxide semiconductor layer, with a surface of the first oxide semiconductor layer located on two sides of the second etch stop layer exposed,
• each of the plurality of second thin film transistors includes a second oxide semiconductor layer formed over a second gate electrode, and another second etch stop layer formed over the second oxide semiconductor layer, wherein the another second etch stop layer partially covers the second oxide semiconductor layer, with a surface of the second oxide semiconductor layer located on two sides of the another second etch stop layer exposed,
• the second etch stop layer and the another second etch stop layer are different from the first etch stop layer, and
• a threshold voltage of the second thin film transistor is higher than a threshold voltage of the first thin film transistor.