Enhanced Photoluminescence Performance of La (P0.5V0.5) O4: 2 at. % Tm3+ Blue-Emitting Phosphors Tailored through Strategic Al3+ Ion Doping

This study presents a comprehensive investigation into the synthesis, structural modulation, and luminescence enhancement of Al3+ co-doped La (P0.5V0.5) O4:2 at. %Tm3+ phosphors, fabricated via a high-temperature solid-state reaction method and subjected to calcination at 1000 °C for 5 hours. These phosphors exhibit prominent blue light emission, with an intense and uniform luminescence peak centered at approximately 459 nm when excited at 359 nm. The observed emission originates predominantly from the characteristic 1D4→3H6 electronic transition of Tm3+ ions, implying their preferential occupancy in highly symmetric sites within the host lattice, optimizing their radiative transition efficiency. To systematically enhance the luminescent performance of La (P0.5V0.5) O4:2 at. %Tm3+, we explored the Al3+ doping impact on the crystallographic structure and optical properties. The experimental results reveal that Al3+ incorporation induces a substantial increase in emission intensity, which follows a concentration-dependent trend initially strengthening with increasing Al3+ content before reaching an optimum level and subsequently declining. The maximum luminescence enhancement was achieved at an Al3+ doping ratio of x = 0.02 in La0.96(P0.5V0.5)Al0.02O₄:2 at.%Tm3+, where the emission intensity was elevated by a factor of 2.05 compared to the undoped La(P0.5V0.5)O4:2 at.%Tm3+ counterpart. Furthermore, these phosphors exhibit highly favorable Commission Internationale de l’Éclairage (CIE) chromaticity coordinates, well-balanced colorimetric parameters, and superior color purity, making them competitive with other reported blue-emitting rare-earth (RE)-doped phosphors. The findings highlight the potential of these phosphors for advanced applications in white light-emitting diodes (WLEDs) and next-generation optoelectronic devices, particularly in enhancing the rendering of blue-hued images in display technologies.