I'm no expert, but you can certainly work with a mentor for your science project. I had
a "mentor" last year in seventh grade, although my project was relatively simple. Plus,
I had access to a past ISEF winner and his mentor, so I didn't have too much trouble as most
people finding help.
But if you are planning on doing a more advanced and involved project, it will be harder to
find a mentor. The fact that you are a middle-schooler, unfortunately, may make professors
and researchers less willing to help you, but this should not be a deterrent. If you keep trying,
it is likely that you may eventually find a mentor.
Although they aren't any people in your area researching in that specific field, you could look
for people who have a thorough knowledge of a more general field related to your subject.
So if you're interested in Quantum Dot solar cells, maybe you could look for people in chemical
engineering or electrical?
What I did was to try and learn as much about my subject as possible and then send an email to
them that showed that I did know what I was doing (to an extent). The email got a little long,
which could have just deterred some professors from wanting to answer it, but I got a response
eventually, so I guess it worked.
I'm just a beginner so my advice probably isn't the best advice, but things worked out for me
and hopefully they will for you.