My iPhone screen is dark but work by seeing under a bright light

While I was uploading 3 of the apps at the same time, the screen went black . My phone screen is dark and the only way I can see anything is with a flashlight. Battery life is good. The touch is working. I can answer calls and do everything I normally do on my phone as long as I'm using a flashlight to brighten the screen. Even I can check my emails, can took pictures, can reset everything in the phone by using a strong flash light. The phone is in perfect condition, there's absolutely no physical damage to it and I have never dropped it in water. I have dropped the phone here and there but always with a case on it so there has never been any physical damage. I did the hard reset, factory reset nothing working to get back the bright screen. So far my phone is working normal, only the back light seems to be gone.

Does the LCD screen replacement will solve the problem?

Or

Is it a problem with motherboard so, I may not able to recover normal bright screen of the phone even replacing the LCD screen?

Thanks a lot in advance.