If you have Bluetooth enabled try to disable it and see if anything changes?
Also take a look at this,
If none of these help try to intentionally put it to sleep and powercycle your laptop when it blackscreens. On next boot up provide the output of
journalctl -r -n 500 -b -1
Maybe the journal contains something useful?
To intentionally put your system to sleep try,
systemctl suspend
or just use the GUI buttons provided by KDE.