Synthesis and warm-white LED applications of an efficient narrow-band red emitting phosphor, Rb2ZrF6:Mn4+

Abstract

Synthesis with low HF concentration or without HF is all along a fundamental challenge in the field of Mn⁴⁺-doped fluoride phosphors for warm-white light emitting diodes (WLEDs). We attempted here to synthesize a red emitting phosphor, Rb₂ZrF₆:Mn⁴⁺, through a two-step co-precipitation method by using H₂O as a solvent instead of the highly toxic HF at room temperature. The structure, morphology and the formation mechanism as well as the effect of dopant concentration on the photoluminescence properties have been investigated systematically. The obtained Rb₂ZrF₆:Mn⁴⁺ phosphor shows intense blue absorption and presents satisfactory red emission with high color purity. The exploration of temperature-dependent luminescence reveals that the resultant sample exhibits preferable anti-thermal quenching behavior (∼103.3% of emission intensity at 120 °C relative to 20 °C) along with excellent color stability in the temperature range of 20–160 °C. Thereafter, the reliability examination in a HTHH (85 °C and 85% high humidity) environment indicates that Rb₂ZrF₆:Mn⁴⁺ exhibits favorable longevity. The device featuring the Rb₂ZrF₆:Mn⁴⁺ red phosphor displays good performance (CCT = 3569 K, R_a = 85.5, LE = 139.1 lm W⁻¹), showing the great potential of the as-synthesized Rb₂ZrF₆:Mn⁴⁺ for indoor lighting applications.