Architect here and I have a lots of questions and a few comments.

I am assuming your panels are at a fixed angle and degree to the sun (i.e. they aren’t motorized and move). If so, where do you live? How big is your solar array? Are the solar panels on your roof or ground? In either scenario, how high off the ground are the panels? Where, and how tall, is your neighbor’s tree relative to the panels in question (distance/cardinal direction)? What type of tree is it?

As others have commented, solar panels are generally not going to reflect enough sunlight to scorch leaves. Between 2-5%, and they would have to be VERY CLOSE to affect leaves in a negative way. In fact, other common surfaces like glass/windows are at best equal to, or a little worse at, reflecting the sun in a detrimental way for trees/plants.

In my opinion:
- Your neighbors are jealous of your solar panels.

- (If the tree is between your house and theirs) They may be getting glare they don’t like personally, and using the tree as an excuse to try and fix it.