With the development of display technology, flat panel display devices, such as a liquid crystal display (LCD), have advantages of high display quality, low power consumption, small thickness and wide range of applications, etc., and thus have been widely used in mobile phones, televisions, personal digital assistants, digital cameras, notebook computers, desktop computers and other consumptive electronic products, and the LCD has become the mainstream of the flat panel display devices.
A polysilicon (PS) thin film transistor (TFT) LCD is different from a traditional amorphous silicon TFT-LCD. Because lattice arrangement of polysilicon is regular, electron mobility of the polysilicon is over 200 cm2/V-sec. In a case that the polysilicon acts as an active layer of the thin film transistor, area of the thin film transistor is effectively reduced, so that aperture ratio is improved, and whole power consumption is reduced while brightness of the display device is enhanced. In addition, in a case that the active layer of the thin film transistor has high electron mobility, a part of drive circuits may be integrated on a glass substrate of the display device, which reduces a number of drive chips and greatly enhances reliability of the LCD panel. Therefore, the polysilicon TFT-LCD, especially a low temperature polysilicon (LTPS) TFT-LCD, has gradually become a research focus in the display field.