From the photos I've seen, no, they are not using triple junction GaAs cells. Boeing/spectrolab cells are incredibly expensive. They used high efficiency 156mm monocrystalline silicon cells. Just not in a glass + aluminum frame like you'd see on a roof.

edit: at least in 2013 they were using thin film amorphous silicon, or what appears to be CdTe thin film flexible, not rigid cells encapsulated in clear lightweight membrane.

https://www.wired.com/images_blogs/business/2013/06/20130609...