Improving LED Efficiency with the New Polymorph β-Ca_1-x Sr_x AlSiN₃ :Eu²

Innovative materials for phosphor-converted white light-emitting diodes (pc-LEDs) are much sought after due to the huge potential of the LED technology to reduce energy consumption worldwide. One of the main levers for further improvements are the conversion phosphors. The system Ca_1-x Sr_x AlSiN₃ :Eu²⁺ currently provides one of the most important red-emitting phosphors for pc-LEDs. We report the discovery of the new polymorph β-Ca_1-x Sr_x AlSiN₃ :Eu²⁺ which allows for significant improvements to LED efficacies. It crystallizes in the orthorhombic space group Pbcn with lattice parameters a=982.43(10) pm, b=575.2(1) pm and c=516.12(5) pm. Compared to α-Ca_1-x Sr_x AlSiN₃ :Eu²⁺ , its emission shows a significantly reduced spectral full-width at half maximum (FWHM). With that, we demonstrated 3 % efficacy increase for white light-emitting pc-LEDs. The new polymorph can easily be industrialised, because the synthesis works on the same equipment as α-Ca_1-x Sr_x AlSiN₃ :Eu²⁺ .