Distortion and energy transfer assisted tunability in garnet phosphors

Solid state lighting based on energy efficient phosphors have never ending demand in the present scenario of high energy consumption of which garnet-based phosphors offer superior advantages owing to the unique structural framework. This review comprehensively examines the advances of photoluminescence and it's tuning through structural modifications and energy transfer (ET) in garnet-based phosphors which includes both self-activated and rare-earth activated compounds. Herein, a very detailed description on the intricacies of the garnet structure composed by the symmetry and the polyhedral representation is included. Regarding structural modifications; which is one of the salient features of this review, first, the tetrahedral distortion assisted luminescence behavior in vanadate garnets is explained in detail. Further, the strong dependence of dipole transitions of Eu3+ with the change in inversion symmetry followed by dodecahedral distortion of various garnet types is elucidated. These findings substantiate the existence of robust interconnection between structural properties and the tunability of luminescence properties in garnet-based phosphor systems. Second, we describe the principles and progress of multicolor garnet phosphors based on single as well as co-doping mechanism and the corresponding ET process through which tuning of white-light emission can be easily realized. In combination of these two methods, systematic tuning of the luminescence can be done through which high efficiency, enhanced thermal stability, true color rendering can be easily attained for garnet phosphors. Accordingly, this comprehensive coverage for understanding the peculiarities of garnets in photoluminescence tuning would promote research on the discovery as well as accelerate further developments in designing garnet phosphors with superior qualities.