Ultra-high photoluminescence quantum yield of Bi3+-doped Cs2ZrCl6 double perovskite micro-crystallites by thermal precipitation in ionic liquids

All-inorganic lead-containing perovskites have shown strong luminescence, but the use of lead has hindered their commercial development due to its stability and toxicity. In this paper, we propose thermal precipitation in ionic liquids (ILs) for synthesizing Bi 3+ -doped Cs 2 ZrCl 6 double perovskites (Cs 2 ZrCl 6 :Bi 3+ (ILs)), which have a better crystallinity compared to the Cs 2 ZrCl 6 :Bi 3+ (HCl) synthesized by the traditional hydrochloric acid method. Most interestingly, the Cs 2 ZrCl 6 :Bi 3+ (ILs) exhibits ultra-high photoluminescence quantum yield (PLQY) of up to 78.52%, which is about three times higher than the Cs 2 ZrCl 6 :Bi 3+ (HCl) prepared by the traditional method. In addition, the PLQY of this paper is the highest in the reported works for the Cs 2 ZrCl 6 :Bi 3+ . It has been confirmed that the high PLQY of Cs 2 ZrCl 6 :Bi 3+ (ILs) is due to the interaction force between N atoms and perovskites in ionic liquid cations, and the cations in ionic liquids can improve the crystallinity of Cs 2 ZrCl 6 :Bi 3+ (ILs) double perovskite crystallites by passivating shallow defects. The research provides an alternative and efficient method for synthesizing stable lead-free double perovskites with good optical properties.