Mechanosynthesis of polymer-stabilized lead bromide perovskites: insight into the formation and phase conversion of nanoparticles

Abstract

The application of polymers to replace oleylamine (OLA) and oleic acid (OA) as ligands for perovskite nanocrystals is an effective strategy to improve their stability and durability especially for the solution-based processing. Herein, we report a mechanosynthesis of lead bromide perovskite nanoparticles (NPs) stabilized by partially hydrolyzed poly(methyl methacrylate) (h-PMMA) and high-molecular-weight highly-branched poly(ethylenimine) (PEI-25K). The as-synthesized NP solutions exhibited green emission centered at 516 nm, possessing a narrow full-width at half-maximum of 17 nm and as high photoluminescence quantum yield (PL QY) as 85%, while showing excellent durability and resistance to polar solvents, e.g., methanol. The colloids of polymer-stabilized NPs were directly processable to form stable and strongly-emitting thin films and solids, making them attractive as gain media. Furthermore, the roles of h-PMMA and PEI-25K in the grinding process were studied in depth. The h-PMMA can form micelles in the grinding solvent of dichloromethane to act as size-regulating templates for the growth of NPs. The PEI-25K with large amounts of amino groups induced significant enrichment of PbBr2 in the reaction mixture, which in turn caused the formation of CsPb2Br5-mPbBr2 and CsPbBr3-Cs4PbBr6-nCsBr NPs. The presence of CsPbBr3-Cs4PbBr6-nCsBr NPs was responsible for the high PL QY, as the Cs4PbBr6 phase with a wide energy bandgap can passivate the surface defects of the CsPbBr3 phase. This work describes a direct and facile mechanosynthesis of polymer-coordinated perovskite NPs and promotes in-depth understanding of the formation and phase conversion for perovskite NPs in the grinding process.

Improving the Stability of Ball-Milled Lead Halide Perovskites via Ethanol/Water-Induced Phase Transition

“…Additionally, the CsPbBr 3 MC solution, which was not synthesized with PAA, was degraded by ethanol and water. Generally, the chemical structure of the ligands affects the optical properties and film morphology of the perovskite NCs [40][41][42][43]. Sichert et al reported that the nanoplatelet thickness could be controlled by the amount of OAm, which could affect the quantum size effect in two-dimensional perovskite [40].…”

“…Sichert et al reported that the nanoplatelet thickness could be controlled by the amount of OAm, which could affect the quantum size effect in two-dimensional perovskite [40]. Jiang et al reported various optical properties depending on the amount of polymer, which improved the stability by forming a shell on the perovskite surface [42]. It has also been reported that the optical properties of perovskite can be significantly decreased by side reactions when polymers or monomolecular ligands are used in excess amounts [42,43].…”

“…Jiang et al reported various optical properties depending on the amount of polymer, which improved the stability by forming a shell on the perovskite surface [42]. It has also been reported that the optical properties of perovskite can be significantly decreased by side reactions when polymers or monomolecular ligands are used in excess amounts [42,43]. Inferior optical properties were also observed when 35 mg of PAA was used to make CsPbBr 3 MC solutions, which could be the result of using an excessive amount of polymer ligand.…”

One-pot synthesis of CsPbBr3 nanocrystals in methyl methacrylate: a kinetic study, in situ polymerization, and backlighting applications

“…[7][8][9] Polymethyl methacrylate (PMMA) has been widely explored as a host polymer because of its excellent optical properties, air resistance, and easy processing, [10][11][12] which promoted the development of PNC-PMMA composites for application in liquid crystal display (LCD) backlights, micro-LED displays, and light communication. [13][14][15][16][17][18] Despite enormous progress made in synthesis methods and device fabrication, PNCs-PMMA still show unsatisfactory efficiency and stability that have become the major obstacles to their practical applications. The ionic surface and dynamic ligand binding induce fast degradation and fluorescence quenching of the PNCs upon exposure to polar solvents, humidity, oxygen, and light.…”

Cu substitution boosts self-trapped exciton emission in zinc-based metal halides for sky-blue light-emitting diodes

“…Metal halide perovskites are promising for next-generation display and lighting applications due to their high photoluminescence quantum yield (PLQY), tunable emission wavelength and low cost, and excellent optoelectronic performance. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] Only five years after the first demonstration of room-temperature electroluminescence (EL) from perovskite light-emitting diodes (PeLEDs), lead-based PeLEDs have already achieved an impressive set of achievements, 17 with the highest external quantum efficiency (EQE) of both green and red light-emitting perovskite diodes exceeding 24% to date. 18,19 However, the development of blue LEDs as a key optoelectronic component is lagging far behind that of green and red LEDs.…”