Hidden Structural Evolution and Bond Valence Control in Near-Infrared Phosphors for Light-Emitting Diodes

We aim to conduct a complete study on the unexpected structure evolution behavior in Cr3+-doped phosphors. A series of Ga2-xScxO3:Cr3+ phosphors are successfully synthesized and confirmed through structural studies, while the lattice parameters change unexpectedly. The unique partial substitution (similar to 87%) of Sc3+ in the octahedral site is demonstrated via Rietveld refinement. Therefore, the bond valence sum calculation explains the reason for this particular Sc3+ concentration. The photoluminescent bandwidth and electron-lattice coupling energy initially increase and then decrease, implying an inhomogeneous broadening effect. Time-resolved spectra and electron paramagnetic resonance are utilized to further examine the subtle change in the microstructures and the second coordination sphere effect of Cr3+center dot Ga1.594Sc0.4O3:0.006Cr(3+) exhibits high internal quantum efficiency (99%) and high phosphor-converted light-emitting diode output power (66.09 mW), demonstrating its capability as an outstanding infrared phosphor. This work will motivate further research on unexpected partial substitution during the solid solution process.

Automated summary

This study focuses on the unexpected structural evolution behavior in Cr3+-doped phosphors and includes the successful synthesis and confirmation of Ga2-xScxO3:Cr3+ phosphors with unexpected lattice parameter changes. It also explores the unique partial substitution of Sc3+ in the octahedral site, as well as the photoluminescent bandwidth and electron-lattice coupling energy changes. The research demonstrates the high internal quantum efficiency and phosphor-converted LED output power of Cr3+-doped Ga1.594Sc0.4O3, indicating its potential as an outstanding infrared phosphor.