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　Bi3+-doped　Cs2ZrCl6　double　perovskites　(Cs2ZrCl6:Bi3+(ILs)),　which　have　a　better　crystallinity　compared　to　the　Cs2ZrCl6:Bi3+　(HCl)　synthesized　by　the　traditional　hydrochloric　acid　method.　Most　interestingly,　the　Cs2ZrCl6:Bi3+(ILs)　exhibits　ultra-high　photoluminescence　quantum　yield　(PLQY)　of　up　to　78.52%,　which　is　about　three　times　higher　than　the　Cs2ZrCl6:Bi3+　(HCl)　prepared　by　the　traditional　method.　In　addition,　the　PLQY　of　this　paper　is　the　highest　in　the　reported　works　for　the　Cs2ZrCl6:Bi3+.　It　has　been　confirmed　that　the　high　PLQY　of　Cs2ZrCl6:Bi3+(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　Cs2ZrCl6:Bi3+(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.　©　2024