monitor

1. Create a batch file named turnoff.bat on your desktop.
2. Open it and add the following line
   powershell (Add-Type '[DllImport(\"user32.dll\")]^public static extern int PostMessage(int hWnd, int hMsg, int wParam, int lParam);' -Name a -Pas)::PostMessage(-1,0x0112,0xF170,2)
3. Save the batch file.
4. Run the file to turn off your screens.There will be a brief command-line window that pops up during execution.

Tested on Windows 10.