How to choose phone case material if heat is the primary criteria?

I have recently purchased an oppo k13 5g and I'm using the case that came with the box. It is an opaque purple case. It was nice but it has started turning yellow which means it's tpu so it's good for heat retention. But it looks awful with all the yellowness. Are all tpu cases like these?

The other option i find are silicone cases which again will cause heat retention and damage the battery. Are there no tpu cases that do not turn yellow?