Blue light from smart phones and computers can dramatically affect sleep quality, by effecting your circadian rhythm (sleep/wake cycle). Thus using computers and smartphones in the evening, can negatively affect your ability to fall asleep and your overall sleep quality.
Here is the solution: Download Flux – Its Free! Flux automatically shifts the colour spectrum of your computer in accordance with the time of day. This simple change can have a dramatic effect on sleep quality, for example when you have to work on your computer in the evenings (which I often do). I have been using it for years and it is something that I always recommend to clients.
In terms of your mobile that is a little trickier, you can get glasses that block the blue light spectrum and as a means to combat this (just google).