Fig. 2: Photoluminescence excitation spectra.
From: Broadband infrared LEDs based on europium-to-terbium charge transfer luminescence
Photoluminescence excitation spectra of Eu2+- and Tb3+-codoped CaS phosphors. Spectra were collected for the Tb3+ 4f–4f emission (545 nm, green solid lines), the Eu2+ 5d–4f emission (650 nm, red and gold solid lines) and the Eu–Tb metal-to-metal charge transfer (MMCT) emission (790 nm, dashed line). The estimated spectral profile of the Eu–Tb MMCT excitation band is highlighted in yellow. The Eu2+ 5d–4f and Eu-Tb MMCT emission spectral profiles are shown in addition (gray dotted lines). All spectra were measured at room temperature.
