Near infrared long-persistent luminescence phosphors are promising for applications ranging from night-vision surveillance to in vivo bioimaging. Here, the authors show that the emission profiles of the near infrared persistent phosphors of Cr³⁺-activated spinel zinc gallogermanate (emission at 650-850 nm) can be significantly improved through incorporation of non-luminescent, divalent calcium into the host lattice. See Xu and Chen, Opt. Mater. Express 7, 2783-2792 (2017).