iPhone6 Screen extreme dark but is still working after overheating

Hi guys,

My sister broke the glass of her screen of her iPhone 6.

I replaced the display by myself. But I couldn't connect one of the connectors well. So I just laid it on the hole. (Later I realised that the connector was broken.)

I powered the phone anyway and it turned VERY hot but the screen stayed black. I couldn't touch it.

So I removed it and connected the display with the broken glass again. It turned on but was very dark. I'm sure it isn't a software problem. I tried an other display and also brought it to a repair shop. But every display stayed dark.

Do you think the temperature sensor is broken? Can it be replaced?