I think as a one off to purely boost the initial charge, would prob be ok .... I'm not the manufacturer n
Sometimes if I've got to be up early, I'll FLASH a torch on my citizen divers watch, for about 2 seconds using a torch, so the glow markers.... GLOW . I've had my watch approx 3 years, and is fully charged but the luminous hands need constant light to stay glowing.
Although I have my phone by the bed, I don't want to burn me eyes turning it on, to time check, but the lil glow from my watch is fine ... I say.lil glow, it's actually quite bright, but not phone bright burning ur eyes! lol