Exploring the potential use of Ca[LiAl3N4]:Eu2+ as phosphor-LED material: Ab-initio calculations

Many materials have emerged recently to replace the non rare-earth red phosphors in aim to achieve high efficiency in converting blue light into white light and replace the old incandescent light bulbs by new light-emitting diodes (LEDs). Nitridolithoaluminate, Ca[LiAl3N4]:Eu2+ has shown to be a narrow band red-emitting phosphor compound with possibility to be used as a high-power phosphor-converted LEDs (pc-LEDs). In this study we were interested in fundamental understanding of the origin of pc-LED activity by a comparative calculation of the optoelectronic properties of Ca[LiAl3N4] and Ca[LiAl3N4]:Eu2+ compounds. We applied the state of art of density functional theory (DFT) to calculate the band gap values. For the parent compound (Ca [LiAl3N4]), we used the modified Becke-Johnson (mBJ) potential with the generalized gradient approximation (GGA). For the doped compound (Ca[LiAl3N4]:Eu2+), we have considered the strong correlation of Eu-f orbitals with GGA + U approach. Throughout the work, we compared the electronic structures and the optical responses for both compounds. Doping with europium leads to a band gap reduction of the parent compound and a strong absorption in higher energy regions (blue to green), which confirm the potential use of doped Nitridolithoaluminate for pc-LEDs.