I agree with deadlifts completely but since I do them on leg day I will suggest something else. The two next best exercises would be chins [ either close grip with palms parallel to each other ( if you can't do wide grip ) or wide grip chins ] and t-bar rows / barbell rows.
If you do deads, chins and rows every back workout I guarantee some nice width and thickness. Keep the form strict and lift heavy and you will grow.