Thin film transistor and method of manufacturing the same

A thin film transistor comprising

• a gate electrode,
• a semiconductor layer overlapping with the gate electrode, the semiconductor layer including a first semiconductor layer and a second semiconductor layer, the first semiconductor layer including a first organic semiconductor material, the second semiconductor layer being farther spaced apart from the gate electrode than the first semiconductor layer, the second semiconductor layer including a second organic semiconductor material, and
• a HOMO energy level of the second organic semiconductor material being different from a HOMO energy level of the first organic semiconductor material;
• and
• a source electrode and a drain electrode that are electrically connected to the semiconductor layer, the semiconductor layer being entirely between the source electrode and the drain electrode, and the first semiconductor layer and the second semiconductor layer both directly contacting the source electrode and the drain electrode.