iPhone case material for best heat dissipation? What case material for iPhone is most effective at dissipating heat. With my current case, my iPhone 11 often feels hot at the bottom of the screen but cools down when I take the case off, so I am confident that the case causes some heat to linger around. I was wondering which material will be best at dissipating heat and if you have any recommendations? TPU, rubber, plastic, metal, silicone, etc?

This is not a shopping recommendation question, rather a material specific question.
You can simply take a physics data book and lookup various materials to see how conductive they are.

Of the ones you list, metal is going to be the most efficient. For example in computers, heat sinks are often made of aluminium.

Note that there usually other properties to take into account when buying a phone case. For example it's hard to find transparent and very flexible metal (i.e. something that will allow you to bend the case slightly to allow you to put in the phone, but won't permanently deform the case).

In some cases those properties can mean that the phone won't be usable for you. For example, I know that you can buy cases with backs made of brushed steel. They are good at heat dissipation, they're flexible for you to put the phone into them easily - but the problem is they also block cell reception and WiFi signals.