Presently, driver circuits in Active-Matrix Organic Light Emitting Diode (AMOLED) panels are generally manufactured using a low temperature poly-silicon process. The currently prevail low temperature poly-silicon process usually uses Excimer Laser Anneal (ELA). ELA refers to performing ELA on an a-Si thin film deposited on glass to make the a-Si thin film converted into a p-Si thin film, i.e., changing from amorphous silicon to poly-silicon. Thus, the field effect mobility of the electrons (i.e., the moving speed of the electrons) is increased by hundreds of times.
Organic Light Emitting Diodes (OLED) are current-driven elements, which means that even a small current variation can result in changes in luminance of the OLEDs, and such changes are reflected as uneven brightness. Taking an AMOLED panel constructed using PMOS transistors as an example, FIG. 1 is a schematic diagram showing a pixel compensation circuit in an OLED driver circuit in related arts. When the OLED emits light, the current IOLED flowing through the OLED is calculated based on the following equation:IOLED=½Coxu W/L(VGS−Vth)2 
where Cox is capacitance of gate oxide layer per unit area of the transistor, u is a channel carrier mobility of the transistor, W/L is a ratio between a width and a length of the channel of the transistor, VGS is a voltage between a gate and a source of the transistor, and Vth is a threshold voltage which enables a driving transistor for driving the OLED to be conducted.
If low temperature poly-silicon is manufactured using ELA, uneven energy control may occur during the ELA process. Thus, the thin film formed by the amorphous silicon is uneven, and the resulted poly-silicon grains are not of uniform size. Consequently, the threshold voltages Vth for enabling the products to be conducted are not uniform. As can be seen from the above equation for calculating IOLED, the light emitting current of OLED is sensitive to the threshold voltage Vth of the driving transistor, and if the Vth is shifted, the current flowing through the OLED will change exponentially. Also, since the light emitting current of the OLED directly influences the luminance of the OLED, the luminance of the AMOLED panel becomes uneven and thereby display defects occur.