Why would a materials researcher use a particle accelerator?

Good question!

While you may have heard that particle accelerators smash particles together, they also release radiation that can be used to study materials. When a charged particle (see What is an electron? What is charge?) is accelerated (it's path is bent along a curve or its speed changes), it releases radiation. This radiation tends to be very bright in a synchrotron and it can be of high energies. This radiation can be passed through a monochromator, which can select out light having only a single energy (only one color). This light can then be used in experiments to image, diffract off of, scatter off of, or be absorbed by samples. We use light diffracted from our sample to determine which crystal structures (phases) are present in our samples. By understanding the conditions under which certain phases are present in our samples and the ways in which different phases transform into one another, we should be able to design more-efficient and less-expensive solar cells, cutting down on unwanted phases in our samples.