All-inorganic tin-doped Cs2BiAgCl6 double perovskites with stable blue photoluminescence for WLEDs

Abstract

Lead-free double perovskites have recently received increasing attention due to their variable band gap. In this work, tin was doped into Cs₂BiAgCl₆ successfully. The doping of Sn²⁺ cations can make the weak white luminescent host to produce pure blue emission peaking at around 464 nm. The internal carrier changes after Sn²⁺ doping and the origin of blue emission in Cs₂BiAgCl₆:Sn²⁺ was analyzed by ultrafast transient absorption (TA) techniques and time-resolved spectra. To further study the substitution feasibility of Sn²⁺–Sn⁴⁺ for Bi³⁺–Bi³⁺ pair cations, Rietveld refinement and density functional theory (DFT) calculations were performed, which proved that the crystal structures of Cs₂BiAgCl₆:Sn²⁺ can exist stably. Based on these observations, we introduced blue-emitting Cs₂BiAgCl₆:Sn²⁺ powder into a white LED fabricated by combining a 340 nm chip to generate stable white light with CIE coordinates of (0.31, 0.34) and a color rendering index value of 83. This work provides the methods to develop environmentally friendly blue emission from lead-free double perovskites at low cost.