1. Press the power button. Sometimes, a screen may simply go black because the device has entered a power-saving mode. Pressing and holding the power button for a few seconds should turn the screen back on.
2. Check the screen protector. If your phone has a screen protector, make sure that it is properly applied and that there are no air bubbles or dirt particles between the protector and the screen. A screen protector that is not properly applied can cause the screen to appear black even when the device is turned on.
3. Connect your phone to a charger. If your phone's battery is low, the screen may go black to conserve power. Connect your phone to a charger and let it charge for a few minutes to see if the screen turns back on.
4. Restart your phone. A simple restart can often fix a variety of issues with your phone, including a black screen. To restart your phone, press and hold the power button for a few seconds until the power menu appears, then tap on "Restart".
5. Check for updates. If there is an update available for your phone, installing it may fix the black screen issue. To check for updates, go to the Settings app and tap on "Software Update".
6. Remove the battery. If your phone has a removable battery, try removing the battery and then reinserting it. This can sometimes fix a black screen issue.
7. Try using the Safe Mode. Safe Mode is a diagnostic mode that allows you to boot your phone with only the essential apps and services running. If the black screen issue does not occur in Safe Mode, it is likely caused by a third-party app. To boot your phone in Safe Mode, press and hold the power button until the power menu appears, then tap and hold on the "Power off" option until the Safe Mode option appears.
8. Factory reset your phone. A factory reset will erase all your data and reset your phone to its original settings. This should be a last resort, as it will delete all your photos, videos, contacts, and apps. To factory reset your phone, go to the Settings app and tap on "General Management", then tap on "Reset" and "Factory data reset".
If none of these steps work, it is likely that your phone's display is damaged and will need to be repaired or replaced.