A device for dimming a display screen includes a pixel driving circuit including a first Thin-Film Transistor, a second Thin-Film Transistor, a third Thin-Film Transistor, a capacitor and a pixel. Signals received by a gate of the first Thin-Film Transistor and a first electrode of the first Thin-Film Transistor correspond to a scanning signal Vscan and a data signal Vdata, respectively. Signals received by a gate of the third Thin-Film Transistor and a first electrode of the third Thin-Film Transistor correspond to a Vpwm signal and a transmitted signal transmitted from a second electrode of the second Thin-Film Transistor, respectively. A second electrode of the third Thin-Film Transistor is connected to the pixel. The capacitor is connected between the gate of the second Thin-Film Transistor and a power supply.