Glad you just didn't say lat's, but total back. That's a good start, and goal, to keep in mind.
Three mass builders for your consideration. All BB'ing reps of 6-10 reps. 2 or 3 sets each. If doing the sets with serious intent, than more sets are not needed...just like everything else in lifting.
DL's are an excellent total back exercise, but perhaps not meant for everyone. Some men are not designed for this exercise (as some are not designed for the squat or bench...truth be told) and sooner or later come up with some unexpected injuries. If using a trap/shrug bar, with the thumbs facing forward and nothing in the way of the knees, than better the chance of getting the most of this total back mass building exercise. And hopefully without injuries. Taller men usually have a problem with a regular straight bar hitting the knees/shines (top DL'ers will usually have skid marks, as some call them, on the shins and knees; bruises, scabs, etc..) Might want to use reps in the range of 6 to 10. At the top standing position of each rep of a DL, shrug the shoulders as high as possible.
BB Rows: A version, which I have seen some very thick & advanced guys doing. is a medium grip row. As the bar raises from the floor, at the same time the upper body begins to straighten up and the exercise becomes more of a combo row and high pull at the finish. A great mass builder for the whole back area. Or the curl grip, medium hand spacing BB row is another effected back builder. Pull the bar to the lower abs as much as you can....pause for 2-3 seconds and lower the bar back to the starting position.
Heavy weighted chins. Medium grip, either curl grip or hammer grip (thumbs back). Alternate grips each workout if you wish. Find one better grip than the other for you, than use it.
Good luck.