Energy transfer between Sm3+ and Er3+ in orthophosphate YPO4

► Synthesis of YPO4:Sm3+, Er3+ for efficient green/red emitting VUV phosphor. ► Host selected according to the position of the ions d bands. ► The energy transfer at low energy is very efficient, but it leads to IR emission. ► Quantum cutting process expected under VUV excitation does not occur at 300 K.