Try freezing bananas with the peels on, and if you want the peels off try dipping the bananas in diet sprite or sprite zero first before freezing!! If you freeze the bananas with the peels on the peel will turn black but the banana should be fine!
Even if it turns brown a bit they are still good for making smoothies or breads. However you really don't want to eat a banana that has been frozen and thawed. You can get this stuff called FRESH FRUIT that you mix and dip or sprinkle on to keep from browning. I've used bananas that have been in the freezer for 6 months or more for my smoothies. While they were brown they were fine.