Is PE Cy7 photosensitive?

Yes, PE-Cy7 is highly photosensitive.  

PE-Cy7 is a tandem fluorochrome composed of R-phycoerythrin (PE) and cyanine dye Cy7. This bright dye is often used as a fluorescence-based indicator in flow cytometry for detecting low-abundance antigens. Its use is immunofluorescence microscopy is limited due to its rapid photobleaching property. The dye degrades rapidly when exposed to photobleaching, higher temperatures and paraformaldehyde fixation.