Biceps are one of your smaller muscles so they don't need as much work to respond. Also, since they're one of the smaller muscles, gains in strength usually come slower just because when you work biceps, you're working mostly biceps as opposed to doing compound movements where multiple muscle groups are involved. So at some point strength gains are going to slow down.
I will recommend first off that you don't try to drastically increase work volume because I doubt this would help you out towards your goal. Might even be counterproductive. I recommend keeping your total work volume low. I know that working out is entertainment in itself but sometimes you have to do less to get more.
I work biceps along with my back twice per week at low volumes; usually 2-3 total sets for biceps each workout, so that's usually around 5-6 total sets for biceps per week. If you work biceps once per week, I'd recommend no more than 5-6 total sets. You could do more but 5-6 good sets would provide enough stimulus.
Also keep in mind that the biceps do a lot of work when you exercise your back. Almost every back movement involves forcefull contractions of the biceps so working the back hard usually means you've hit your biceps hard. What you don't get during back training is full range of motion contraction, which is why some isolation work is a good idea if you're intersted in physique asthetics.
Getting to the main point: If you want stronger biceps, concentrate on your back work. If your back strength increases your biceps usually follow suit. Just keep hammering away with your biceps specific training as supplemental work, but just make sure not to overdo it.
If strength is your main goal for biceps, concentrate on the lifts that allow you to use the most weight: heavy barbell curls and weighted close-grip chins. Usually out of my 5-6 sets per week, at least 4 come from heavy barbell curls (6-8 full reps with slow negatives) and the other sets come from exercises such as incline DB curls, alternating DB curls or preacher curls.
Strong back, strong biceps. When you're doing your full range of motion work, make sure you're going through the fullest range of motion. If you add extra weight and can't get the full range of motion you're just selling yourself short.
I've used cheat curls before as well. You can do a set of barbell curls to the point where you can't do any more full range of motion reps, add some weight (5-10 extra pounds) and do a few more reps where you deliberately cheat to curl the bar up. You don't want to cheat a lot, but just enough to curl the bar. Other muscles will be helping you lift the bar but the biceps are still going to be working hard (so other muscles are allowing the biceps to continue to work). You'd still want to lower the weight slowly and under control.
That's about all I can think of for biceps. Biceps are a fairly simple muscle and the ways in which you train it are also simple. A lot of people treat biceps like abs and tend to overanalyze them.
Good luck, bro.