Compositional and Dimensional Control of 2D and Quasi-2D Lead Halide Perovskites in Water

Blue light emitting two dimensional (2D) and quasi-2D layered halide perovskites (LHPs) are gaining attention in solid-state lighting applications but their fragile stability in humid condition is one of the most pressing issues for their practical applications. Though water is much greener and cost effective, organic solvents must be used during synthesis as well as the device fabrication process for these LHPs due to their water-sensitivity/instability and consequently, water-stable blue-light emitting 2D and quasi-2D LHPs have not been documented yet. Here, water-mediated facile and cost-effective syntheses, characterizations, and optical properties of 16 organic–inorganic hybrid compounds are reported including 2D (A′)₂PbX₄ (A′ = butylammonium, X = Cl/Br/I) (8 compounds), 3D perovskites (4), and quasi-2D (A′)_pA_x−1B_xX_3x+1 LHPs (A = methylammonium) (4) in water. Here, both composition and dimension of LHPs are tuned in water, which has never been explored yet. Furthermore, the dual emissive nature is observed in quasi-2D perovskites, where the intensity of two photoluminescence (PL) peaks are governed by 2D and 3D inorganic layers. The Pb(OH)₂-coated 2D and quasi-2D perovskites are highly stable in water even after several months. In addition, single particle imaging is performed to correlate structural–optical property of these LHPs.