CsPbBr3@SiO2 Core–Shell Nanoparticle Films for Superhydrophobic Coatings

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 SiO2 layer with surface modification by intrinsically hydrophobic methyl groups for the fabrication of superhydrophobic SiO2-coated CsPbBr3 (referred as SH-CsPbBr3@SiO2) nanoparticle films. The SiO2 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-CsPbBr3@SiO2 core–shell nanoparticle film can reach 160 and 3°, respectively. As a synergetic contribution from SiO2 coating and modification by methyl groups, the as-fabricated green-emissive SH-CsPbBr3@SiO2 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-CsPbBr3@SiO2 sample increases by 46% after 180 days under ambient conditions due to the phase transformation from CsPbBr3 to CsPb2Br5 and Pb(OH)Br. The resulting CsPb2Br5-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.