(gci C:\Scripts -r | ? {$_.PSIsContainer -eq $True}) | ?{$_.GetFileSystemInfos().Count -eq 0} | select FullName
(replace C:\Scripts with the root directory)
Output example:
FullName
-------
C:\Scripts\Empty
C:\Scripts\Empty Folder 2
C:\Scripts\Empty\Empty Subfolder
C:\Scripts\New Folder\Empty Subfolder Three Levels Deep