Enhanced photoluminescence efficiency and stability of CsAgCl2 by a NaCl-assisted synthesis

Abstract

Abstract Here, a NaCl (x = Na/Ag = 0.5) assisted strategy was used to synthesize pure phase CsAgCl2 micro-crystals (MCs) with enhanced photoluminescence (PL) efficiency and stability. Adding a certain amount of NaCl during the preparation could result in high purity of final CsAgCl2 products and higher photoluminescence quantum yield (PLQY), better heat, UV light irradiation, and moisture stability. The CsAgCl2 MCs synthesized in this study displayed a wide PL spectrum spanning from 350 to 750 nm, featuring a peak emission at 544 nm and achieving a remarkable peak PL quantum yield (PLQY) of 73%. The extensive PL spectrum and a substantial Stokes shift of 260 nm provide evidence for the emission mechanism attributed to self-trapped excitons (STEs) within the CsAgCl2 MCs. The dual STE emission originated from two emitting triplet excited states and was observed in the low-temperature PL spectra. A thermal-assisted energy transfer happened with the temperature increase (10~300K), contributing to the efficient STE emission of CsAgCl2 MCs. In conclusion, the pristine CsAgCl2 MCs were employed as a sole phosphor material for encapsulating a 270 nm UV chip for white light-emitting diode (WLED) applications. Despite exhibiting a half-lifetime of 35 minutes under a continuous driving current of 10 mA, the WLED demonstrated notable stability in CCT, CRI, and CIE color coordinates. The resulting device emitted warm white light, characterized by Commission Internationale de l’Éclairage (CIE) color coordinates of (0.48, 0.45), a low correlated color temperature (CCT) of 2734 K, and a high color rendering index (CRI) of 81.9. These results demonstrated the unique advantages of CsAgCl2 MCs in high-performance single-phosphor WLEDs.