You're acting all surprised, but it's not like this is something new. This is very basic electronics engineering stuff.

A car is also designed to run most efficiently at around 92 degrees C engine temperature. Fuel efficiency goes down if you deviate too much from that, and by a lot more than 25%. Surprised too?

The reason solar panels are optimized for the temperatures they are, is exactly because, guess what, that's the temperature range they function in most of the time.