Check the following steps to fix black screen error:Pause on the ‘Power’ button
Hold on the ‘Power’ button for at least 30 seconds, after taking out your system’s battery and removing its AC adapter cord.
Reconnect your laptop
Once you hold on the ‘Power’ button for 30 seconds, reconnect your laptop to the wall power as pausing on the power button drains any static electricity causing the black screen.
Replace the battery
Mostly, a worn out battery causes the black screen of your laptop. You should replace it with a newer one.
Get more help to fix dell black screen error:http://supportfordell.iyogi.com/inspiron-15z/black-screen-11.html
Hope this helps you.