See Why You Should Never Sleep With TV or Dim Lights On

Scientists are unanimous and say that sleeping
should take place in total darkness. When the sun
rises and daylight appears, our light receptors send
a clear message to the brain that it is time to wake
up. When darkness falls, the brain receives a signal
that it is time to sleep, so sleep hormone is
released. If during sleep you are exposed to a light
source, you will have a restless sleep.
This is because light significantly affects bodily
functions and rhythm of sleep and wakefulness.
Restless sleep, which occurs from sleeping under
light, can result in bad mood, sleepiness, and
difficulty in waking up.
Neurological studies have shown that sleep with
turned on PC or TV or any other light leads to bad
mood.
Therefore, if you have a habit of sleeping with the
TV or computer turned on, you need to try to get
rid of this bad habit as quickly as possible.
If you cannot sleep without a TV, then set the timer
on in order to reduce the consequences of poor
sleep.