Flexible semiconductors have enough speed to drive OLED pixels
The excellent performance of molybdenum disulfide as a 2D semiconductor material is that they are easily bendable. Electrons can move quickly in such semiconductors. At the same time, such semiconductors are transparent because they are only about one atom thick. These features make them ideal materials for making flexible OLED displays.
There is now a way to apply molybdenum disulfide transistors to flexible OLED displays. They used this transistor to form a simple 6×6 dot matrix on a plastic sheet that was only 7 microns thick. This plastic sheet could be attached to human skin. This simple plastic sheet display is very soft and will not break if bent with a bending radius of less than 1 cm.
A molybdenum disulfide transistor is sandwiched by two layers of aluminum oxide (Al2O3) from above and below. This kind of device has high mobility, and high mobility is very important for the current of the pixels of the OLED display.
The contact resistance between molybdenum disulfide and the transistor electrode is very high, and the high resistance reduces the carrier mobility of the molybdenum disulfide transistor. The key to solving the problem lies in recognizing that 2D semiconductors are very susceptible to the surrounding materials. It is different from the common method of placing transistors on a silicon oxide surface.
The material surface is very smooth and easy to control. They sandwich the transistor in two layers of insulating aluminum oxide. The contact surfaces of Al2O3 and MoS2 increase the electrons in the semiconductor, similar to the doping of chemicals in the silicon material to make it a semiconductor phenomenon. This enhanced effect overcomes the problem of high contact resistance and increases charge carrier mobility. In addition, smooth dielectric materials do not generate spots that can trap charge, further increasing the mobility to 17 to 20 cm2/Vs。