With the screen off, of course.
Leaving the screen on while charging is equivalent to keeping the phone awake, so keeping it awake will consume more power. In this way the charging speed will be much slower. In addition, charging time, playing mobile phones, also have great damage to the battery, wake up state and play mobile phones are about the same, it is equivalent to charging while playing at hand consumption of electricity, that is, for the battery, on the one hand into the power while also out of the power, the service life of the phone battery will be cut short! I have a feeling that when the phone is charging and then wake up the screen, the phone will be more and more hot, the more rushed the hotter, the technology is better to close the screen.
All right, no impact, long time on the screen, slow charging, screen life is short