Dual-Band White Light Emission and Temperature-Dependent Luminescence of Sn2+ in the Metastable Structure of Cs2CaCl4(H2O)2

Abstract

The quest for novel luminescent materials with tunable color emission and temperature-sensing capabilities remains a vibrant field of research, particularly for applications in solid-state lighting and security features. In this study, the as-synthesized a rod-like crystal Cs2CaCl4(H2O)2:Sn2+ (R-CCCH:Sn2+) exhibits dual- band white light emission characterized at 415 nm and 540 nm, which are correspond to the singlet state and triplet state transitions of Sn2+, respectively. Upon heating from 298 to 428 K, an anomalous enhancement in the intensity of the 415 nm emission in R-CCCH:Sn2+ was observed while its 540 nm emission underwent significant thermal quenching. The observation of the temperature-dependent photoluminescence (PL) indicates that R-CCCH:Sn2+ exists in a metastable state. Upon calcinating at 428 K for 20 min, the R-CCCH:Sn2+ changed to the stable state P-CCCH:Sn2+, exhibiting the STEs of CCCH matrix and the 3P1→1S0 transition of Sn2+. The significance of this work lies in the discovery of the metastable state in CCCH and the manipulation of Sn2+ to emit both singlet and triplet transitions, leading to white light emission.