A free app for Android, by RADEFFFACTORY.

Double Click Lock – Double Tap is a handy tool to help you to quickly and easily turn off the display of your Android device. It can be used as an alternative to the hardware switch and can be useful when you need to use your phone for a long period of time.

It is a very easy and convenient way to put the device into sleep mode, as it only requires you to double tap the screen.

If you need to use your fingerprint or face to unlock your device, you should not use this app. It is a Android limitation and cannot be avoided at the moment.