Everyone wants that wide/thick back (get your head out the gutter guys) and here is an effective back routine:
-pull ups 3 sets of 10-15 reps (if you can do that easily i would add weight by using a belt or if you cant do pull ups i would go and use the lat pull down machine until you build up enough strength to do pull ups).
-t bar rows 4 sets adding weight each set starting with 12-10-8-6 reps.
-barbell row 4 sets also adding weight each set starting with 12-10-8-6 reps.
-deadlifts 5 sets of 5 adding weight every set for example i start with 135 then go to 225,315,365,405
-cable row 4 sets of 12-10-8-6 reps adding weight and squeezing the back at the end of the movement.
I put the exercises in the order that i do them but feel free to switch them around and get to it! This is not for everyone so start slowly and work your way up by maybe only doing 3 sets of each exercise or choose at least one row, a pull down and the deadlift.