Switchable Anion Exchange in Polymer-Encapsulated APbX₃ Nanocrystals Delivers Stable All-Perovskite White Emitters

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, PbBr 2 , 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/cm 2 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.

Highly Emitting Perovskite Nanocrystals with 2-Year Stability in Water through an Automated Polymer Encapsulation for Bioimaging

“…Examples are polymer-SiO 2 shelling, 12 amphiphilic polymer or solid–lipid encapsulation, 13 , 14 synthesis of structures with reduced dimensionality, 15 doping, 16 use of bulky ligands, 17 − 22 incorporation of NCs in a polymeric matrix, 23 − 27 or their preparation within polymeric nanoreactors, 28 , 29 which had recently allowed reversible halide exchange. 30 While all these techniques have clear advantages, it remains a challenge to simultaneously preserve the high PLQY and synthetic flexibility of the original colloidal NCs while also providing a stable dispersion in water over long times. Moreover, current protocols require a long preparation time, multiple encapsulation steps in different materials, and their scalability has not yet been proved.…”

Polyacrylic acid-b-polystyrene-passivated CsPbBr3 perovskite quantum dots with high photoluminescence quantum yield for light-emitting diodes

“…When CsPbBr 3 @PAA- b -PS PQDs were suspended in toluene, the polymer PS maintained the coil state, and the larger the ratio of –COOH, the stronger the force between the block polymer and the PQDs, making the PL strength stronger. 27 Therefore, we selected PAA 24 - b -PS 206 as the ligand with a concentration of 5 mg mL −1 and a reaction time of 24 h as the optimal process for the preparation of CsPbBr 3 @PAA 24 - b -PS 206 PQDs.…”

Polystyrene‐based Macromolecular Ammonium Halides for Tuning Color and Exchange Kinetics of Perovskite Nanocrystals

“…Simple, solution methods to control exchange would have advantages over other useful methods, such as capping NCs with lead sulfate [28] or confinement in porous silica [29] . Prior studies using copolymer encapsulation to arrest halide migration [30] utilized precipitation into non‐solvents followed by ball milling of the mixture.…”