Enhancing dual emission in double perovskites Sb3+-doped Cs2Na0.6Ag0.4InCl6 through structural and energy level modulations for near-solar broad spectrum white LED

Lead-free perovskites that exhibit exceptional stable, effective, and non-toxic have generated significant interest. Notably, cesium sodium indium chloride (Cs2NaInCl6) double perovskites possess these desirable properties, yet their restricted optoelectronic performance within the visible spectrum hinders their widespread adoption in emerging solid-state lighting technologies. Solid-state lighting applications stand to gain significant advantages from the white light emission achievable through a single emitter. Through the introduction of Ag+ and Sb3+ in Cs2NaInCl6, we have succeeded in generating dual emission in a composite, resulting in blue and yellow light emission. This was confirmed through analysis using UV-visible absorption spectroscopy, temperature-dependent photoluminescence (PL), and first-principles density-functional theory. The absorption peak of Cs2Na0.6Ag0.4InCl6: x% Sb is a broad peak, unlike that of Cs2Na0.6Ag0.4InCl6, indicating that doping with Ag+ and Sb3+ leads to changes in the energy level structure without causing a distinct phase transition. Cs2Na0.6Ag0.4InCl6 violates the commonly observed forbidden transition rule. Ag+ doping influences the self-trapped exciton luminescence center, leading to the emergence of new yellow emission peaks that do not diminish the blue emission. The Ag+-induced [SbCl6](3-) octahedral Jahn-Teller deformation contributes to the blue emission, which represents the self-trapped exciton emission. Conversely, the yellow emission originates from Ag+ doping's STE emission. By adjusting the Sb3+ doping ratio, it is possible to optimize the blue, yellow, and white light emissions for high-performance near-solar broad-spectrum white LED devices.