Tunable ultra-broadband full-visible-spectral emission of Bi3+-doped aluminate phosphors enabled by structure transformation and site occupancy engineering

Abstract

Inorganic phosphors with tunable broadband emission have important applications in solid-state lighting and security anti-counterfeiting. Therefore, developing materials with simultaneous requirements of spectral tunability and ultra-broadband emission is significant for artificial lighting applications. In this work, we develop a series of solid-solution phosphors with tunable broadband emission, Na_yCa_9−x−y/2Al₆O₁₈:xBi³⁺ (0.005 ≤ x ≤ 0.04, 0.625 ≤ y ≤ 2). The structure transformation and site occupancy engineering of Bi³⁺ in Na_yCa_9−x−y/2Al₆O₁₈ phosphors are demonstrated. Due to the structural transformation and multi-site occupation of Bi³⁺, an ultra-broad full-visible-spectral emission can be realized in single phased Na₂Ca_7.98Al₆O₁₈:0.02Bi³⁺, which simultaneously exhibits visual spectral tunability through site-selective excitation. A simplified packaging technology is proposed to fabricate a white light emitting diode (WLED) based on only Na₂Ca_7.98Al₆O₁₈:0.02Bi³⁺ phosphor and an ultraviolet LED chip, with a CCT of 5577 K and high color rendering index (R_a = 84.2). Moreover, the optical anti-counterfeiting application is demonstrated by using the screen-printing technique. Our findings not only suggest a novel strategy to develop tunable ultra-broadband full-visible-spectral luminescence phosphors but also pave a new way to explore more efficient ultra-broadband phosphors for multi-functional photonic applications.