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

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, NayCa9-x-y/2-Al6O18:xBi(3+) (0.005 <= x <= 0.04, 0.625 <= y <= 2). The structure transformation and site occupancy engineering of Bi3+ in NayCa9-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 Na2Ca7.98Al6O18:0.02Bi(3+), 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 Na2Ca7.98Al6O18:0.02Bi(3+) 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.