Abstract
We report a one-step synthesis of halide perovskite nanocrystals embedded in amphiphilic polymer (poly(acrylic acid)-block-poly(styrene), PAA-b-PS) micelles, based on injecting a dimethylformamide solution of PAA-b-PS, PbBr2, ABr (A = Cs, formamidinium, or both) and “additive” molecules in toluene. These bifunctional or trifunctional short chain organic molecules improve the nanocrystal–polymer compatibility, increasing the nanocrystal stability against polar solvents and high flux irradiation (the nanocrystals retain almost 80% of their photoluminescence after 1 h of 3.2 w/cm2 irradiation). If the nanocrystals are suspended in toluene, the coil state of the polymer allows the nanocrystals to undergo halide exchange, enabling emission color tunability. If the nanocrystals are suspended in methanol, or dried as powders, the polymer is in the globule state, and they are inert to halide exchange. By mixing three primary colors we could prepare stable, multicolor emissive samples (for example, white emitting powders) and a UV-to-white color converting layer for light-emitting diodes entirely made of perovskite nanocrystals.
Highlights
We report a one-step synthesis of halide perovskite nanocrystals embedded in amphiphilic polymer (poly(acrylic acid)block-poly(styrene), PAA-b-PS) micelles, based on injecting a dimethylformamide solution of PAA-b-PS, PbBr2, ABr (A = Cs, formamidinium, or both) and “additive” molecules in toluene
= Cl, Br, color is tunable across the ultraviolet−visible spectrum and beyond, by alloying, doping, or anion/cation exchange.[6,8,11−14] These NCs are coated with surfactant molecules that stabilize them in nonpolar or moderately polar organic solvents.[15−18] Yet, the
Polymeric micelles have been used as templates to synthesize inorganic NCs with low polydispersity and a stable surface coating.[47−50] Polymers with hydrophobic characteristics are ideal choices to protect MHP NCs from polar solvents and have been widely tested in this regard.[51−57] For example, previous studies have shown that embedding CsPbBr3 NCs in different polymeric matrices significantly improves the stability of such NCs.[58]
Summary
When protected from anion exchange (for example, when dispersed in polar solvents, or as dried powders), nanocrystals emitting at different colors can be mixed together and the resulting sample preserves the multicolor emission over time Such color stable samples were further used to prepare fully halide perovskitebased nearly white emitters (and a white light emitting device based on UV-to-white color converting layer) by mixing three primary colors. Materials and methods, extended literature review, table of comparison of key features, TEM, DLS, XRD, and NMR analyses, role of various additives on the stability of perovskite NCs in polar solvents, optical absorption and table of optical properties, PL lifetimes, and PL decay curves, switchable halide exchange reactions, aging tests, synthesis and photographs of PAA-b-PS-encapsulated FAPbBr3 NCs, additional data on emitting powders and on the white light emitting layer preparation (PDF).
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