The Sony PlayStation 3 makes use of either a Sixaxis or a Dualshock 3 controller via a Bluetooth connection. By design, both the Sixaxis and the Dualshock 3 are almost identical to earlier PlayStation controllers, including the original Dualshock for the PlayStation and the Dualshock 2 for the PlayStation 2, with the addition of a "PS" button used to bring up the Cross Media Bar. This "PS" button is key to turning the controller on and off.
Turning Off the Controller
Press and hold the "PS" button on the controller for a few seconds. An Options menu will pop up.
Select “Turn Off Controller” and press the "X" button.
The controller will then shut off, saving battery life while you take advantage of the PS3s other media capabilities such as watching a movie or listening to music.