Multicolor light emission and multifunctional applications in double perovskite-Cs₂NaInCl₆ by Cu⁺/Sb³⁺ co-doping

Halide double perovskites managed by metal doping approach can exhibit dual emission colors, which have been considered as promising multicolor luminescent materials. However, an independent and stable emission at yellow region is missing owing to limited doping candidates, hindering the further commercialization of multicolor luminescence applications in double perovskites. In this work, we successfully obtain stable multicolor emission with PLQE (photoluminescence quantum yield) as high as 78% through developing the Cu^I doping strategy in Sb-Cs₂NaInCl₆. By introducing a high Cu^I feed ratio in airtight autoclave to compete the oxidization effect, the oxidization of Cu^I into Cu^II (detrimental factor for high PLQE due to serious quenching effect) is largely suppressed. With changing the Cu^I feed ratio, at least four distinct emission colors ranging from blue, purple, pink to yellow can be realized via changing the excitation wavelength. Depending on tunable multicolor emission, we further demonstrate the promise of our co-doped double perovskites in anti-counterfeiting technology and multicolor lighting devices. Our results open the way for enriching the optical applications of double perovskites based on multicolor emission.