Black Lines on iPhone screen

Please Someone help me about my iPhone screen

Horizontal Black lines are appearing on screen. This happens once in a 3 months and gone to normal after couple of days, sometimes I use some tricks to make it normal, like flashing RGB colours on screen or reducing White Point. But Today its not working.

I want to know exact cause and solution for this.

I observe following things

• Usually this happens after using phone on full brightness for very longtime (Watching 4 movies back to back)
• Or after using phone on full brightness while changing
• Or after Keeping stationary image on screen for long time (Chating for long time keeps keyboard ON screen this affects bottom part, and start showing keyboard impressions on black image in green lines)

Photos

1. Shows black lines on screen
2. Shows how pure black image look like
3. Shows how pure black image look like