I tend to get better quality sleep when I am exercising in some way, bike commuting included.
I hate waking up, but once up I actually quite enjoy the early start on the day. I find that I really need 8 hours of sleep to feel rested and restored, so for me that means a goal of turning out the light and closing my eyes no later than 10PM. If I want to read, etc, I head to bed around 9-9:30.
This is tough to do in Summer due to the fact that the sun stays up past 9, but I feel so much better when I keep to an earlier evening schedule.
I find that having an evening ritual of packing my next day's clothes, etc, into the panniers and getting my riding clothes ready to wear is a way for me to transition to bedtime with no anxiety about being ready for the next morning's commute.