Broadband cyan-blue emitting Y4Al2O9:Ce3+phosphor with high quantum efficiency, thermal stability and water resistance for w-LEDs, papiloscopy and fraud prevention systems

In this study, we introduce a novel cyan-blue emitting monoclinic Y4Al2O9:Ce3 << (YAM:Ce3 <<) phosphor, which exhibits exceptional potential for white light emitting diode (w-LEDs) lighting. These phosphors, doped with varying concentrations of Ce3 << (1-5 %), are synthesized via a combustion method, and their structural, photoluminescence (PL), chromatic, and quantum efficiency characteristics are thoroughly analyzed. Under 350 nm excitation, the YAM:Ce3 << phosphor exhibits a robust cyan-blue emission band peaking at 450 nm, attributed to the 5d -> 4f transition of Ce3 << ions. The optimized 3%Ce3 << doped YAM (YAM:3%Ce3 <<) phosphor demonstrated an internal quantum efficiency (IQE) of 76.78 % and an external quantum efficiency (EQE) of 51.76 %, along with excellent thermal stability, retaining 78.87 % of its original emission intensity at 423 K. Remarkably, after 200 days of water immersion, its luminous intensity remained unchanged, confirming its outstanding water resistance. To demonstrate its applicability, a w-LED device is fabricated using a 365 nm near-ultraviolet (n-UV) LED chip combined with YAM:3%Ce3 << (blue), commercial (Ba, Sr)2SiO4:Eu2 << (green) and CaAlSiN3:Eu2 << (red) phosphors. The device exhibited bright warm-white light with an impressive colour rendering index (CRI) of Ra = 95.5 (R9 = 67.2, R12 = 88.7) and a low correlated colour temperature (CCT) of 4043 K. Furthermore, YAM:3% Ce3 << phosphor is utilized for developing latent fingerprints (LFPs), offering high selectivity, contrast, and precise identification of Level I-III fingerprint details. Additionally, its application as a security ink highlights its potential for encryption and anti-counterfeiting (AC) technologies. This study provides valuable insights into designing next-generation broadband blue-emitting phosphors for applications in high CRI w-LEDs, LFPs analysis and AC security measures.