Lead halide perovskite (LHP) nanomaterials have attracted tremendous attention owing to their remarkable optoelectronic properties. However, they are extremely unstable under moist environments, high temperatures, and light illumination due to their intrinsic structural lability, which has been the critical unsolved problem for practical applications. To address this issue, we propose a facile and environmentally friendly ligand-free approach to design and synthesize rod-like CsPb 2 Br 5 -embedded Pb(OH)Br with excellent stability under various harsh environments such as soaking in water, heating, and ultraviolet (UV) illumination. Plate-like CsPbBr 3 -and Cs 4 PbBr 6 -embedded Pb(OH)Br powders are first formed by evaporating the solvent in a dispersion of ethanol (or methanol, isopropanol), Cs 2 CO 3 , and PbBr 2 . Upon soaking in water, the plate-like sample undergoes phase transformation from CsPbBr 3 and Cs 4 PbBr 6 to CsPb 2 Br 5 and shape conversion from nanoplate to a microrod, leading to the formation of rod-like CsPb 2 Br 5 -embedded Pb(OH)Br. The stable Pb(OH)Br coating effectively prevents the luminescent CsPb 2 Br 5 nanocrystals from reacting with water, leading to extremely high aqueous stability of the CsPb 2 Br 5 -embedded Pb(OH)Br. The photoluminescence (PL) intensity of the representative CsPb 2 Br 5 -embedded Pb(OH)Br sample can maintain 92.2% of the initial PL intensity value even after soaking in room-temperature water for 165 days; in the meantime, the phase and shape are preserved. The typical sample also shows outstanding stability under hot water, UV illumination, and annealing conditions. The ultrahigh aqueous stability, thermal stability, and photostability of the CsPb 2 Br 5 -embedded Pb(OH)Br nanomaterials suggest an effective, facile, and environmentally friendly technique to grow perovskite-based nanomaterials for promising practical applications in the optoelectronic field.
Lead halide perovskite nanocrystals are extremely promising for photoelectronic application. However, maximizing their stability toward water, UV irradiation, or heat is yet a great challenge for the commercialization process. Herein, we develop a novel and facile surface functionalization approach that combined coating by the SiO 2 layer with surface modification by intrinsically hydrophobic methyl groups for the fabrication of superhydrophobic SiO 2 -coated CsPbBr 3 (referred as SH-CsPbBr 3 @SiO 2 ) nanoparticle films. The SiO 2 coating is realized by the hydrolysis of tetramethyl orthosilicate in the presence of ammonia. Hexamethyldisilazane is introduced for nanoparticle surface modification and thus offers the nanoparticle films' superhydrophobic performances. By optimizing the surface coating and modification, the static water contact angle and sliding angle on the representative SH-CsPbBr 3 @SiO 2 core−shell nanoparticle film can reach 160 and 3°, respectively. As a synergetic contribution from SiO 2 coating and modification by methyl groups, the as-fabricated green-emissive SH-CsPbBr 3 @SiO 2 films exhibit excellent water repellency, self-cleaning, and ultrahigh stability toward water, heat, and UV illumination. It is of great interest that the photoluminescence (PL) intensity of the SH-CsPbBr 3 @SiO 2 sample increases by 46% after 180 days under ambient conditions due to the phase transformation from CsPbBr 3 to CsPb 2 Br 5 and Pb(OH)Br. The resulting CsPb 2 Br 5 -based luminescent film shows excellent aqueous stability with remaining 75% of its initial PL intensity after soaking in water for 10 days. The white-light-emitting diode device fabricated using the green-emissive nanoparticles reports more than 20% external quantum efficiency (EQE), and no noticeable decrease in EQE is observed even after 2 weeks. This work elucidates a facile surface engineering strategy to prepare luminescent films with ultrahigh stability.
Deposition of covellite CuS nanocrystals on the multilayered MXene and few-layered MXene by a facile reaction of S2− with Cu2+ precursors to obtain 0D/2D nanocomposites.
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