High concentration quenching, improved PLQY and high color purity of novel Gd2TiO5:Eu3+ triggered by complete solubility of dopant

Abstract

In the surge of new inorganic luminescent host for lanthanide ion for efficient solid-state lighting, Ln2TiO5 comes as a new class of materials with all optically suited properties. Triggered by very high solubility of Eu3+ ion in Gd2TiO5 with minimal lattice strain, negligible doping induced structural distortion and no charge compensating defects; Gd2TiO5:Eu3+ (GTOE) delivered an extraordinary credentials as novel phosphor material. GTOE demonstrated no concentration quenching up to 10 mol % doping; monotonic rise in emission intensity, higher excited state lifetime, high red color purity∼99% and PLQY∼ 14%. Luminescence lifetime spectroscopy suggested stabilization of Eu3+ in both GdO7 with distorted pentagonal bipyramid (DPB) and distorted hexagonal bipyramid (DHB) geometry having similar coordination and symmetry and is well supported by two stark components in 5D0→7F0 transitions. Positron annhilation lifetime spectroscopy (PALS) suggested that average positron lifetime remained constant in all the samples indicating no charge compensating defects formation further justifying occupancy of Eu3+ in isovalent Gd3+ site. Judd-Ofelt analysis suggested that local symmetry around Eu3+ ion and polarizability of Eu–O bonds in GTO host doesn't change throughout the concentration range. This work proposed an excellent candidate for red emitting materials towards phosphor converted white light emitting diodes (pcLEDs) having high dopant solubility, PLQY and color purity.