How do I turn my laptop monitor off when I have an external monitor?

I currently installed an external monitor, which works fine, but I only want my fair to show on the external monitor, not both screens. I cognize I can press Fn + F6 to turn off the laptop screen manually, but the next time I turn my computer on the laptop screen will be back on once more. It's not a major problem, but I was just wondering if there was a way of making it so that the laptop monitor was off when I turned the computer on.