Improvement in optical properties of Cs₄PbBr₆ nanocrystals using aprotic polar purification solvent

Abstract

We demonstrate the influence mechanism on the optical properties of Cs4PbBr6 during purification of solutions with different protonated levels and polarities.

Electrochemically Quantifying the Phase Transition of Cesium Lead Halide Perovskite Quantum Dots in Purification

“…Regarding the PeQDs, a rigorous purification is required after synthesis to remove unreacted precursors and excess ligands, since their existence results in poor film quality and hence inferior performance in optoelectronic devices. , This process involves the use of polar solvent to precipitate PeQDs and is crucial for obtaining PeQD ink of good quality. Specifically, it has been demonstrated that the polarity and amount of the polar solvent used in purification process have an effect on the size, morphology, and degree of crystallization of PeQDs. Polar solvents such as ethyl acetate (EtOAc) and methyl acetate (MeOAc) can etch organic groups on the surface of nanocrystals, increase the surface energy, and cause surface reconstruction.…”

Solvent Evaporation Induced Large-Scale Synthesis of Cs4PbBr6 and CsPbBr3 Microcrystals: Optical Properties and Backlight Application for LEDs

“…The comparison PL substantiates that the 3D counterpart exhibits low PL due to lower exciton binding energy (19–60 meV) causing the free charge carriers to dissociate and travel all through the octahedra which are corner shared thereby reducing the probability of fast radiative recombination. ,, The PL spectra at different excitation wavelengths (Figure S5b) imply that the maximum emission intensity occurs at 365 nm compared to all other wavelengths showing its wavelength dependence. It is clear that Cs 4 PbBr 6 is a direct band gap material with its intrinsic band gap ranging from 3.2 to 3.9 eV . But due to the existence of Br vacancy, Cs 4 PbBr 6 portrays two band gaps of (i) ∼2.34 eV associated with the defect state sub band gap and (ii) 3.6 eV attributed to its intrinsic band gap (Figure d) calculated as per Cs 4 PbBr 6 by Kubelka Munk theory. ,, The inset of Figure d shows the sub band gap plot arising due to Br vacancies corresponding to the band gap of 2.34 eV.…”

“…or involves complex procedures . Also, most of the synthesis methods are focused on developing fluorescent perovskite quantum dots rather than in the bulk perovskite microcrystal form which is non-fluorescent in most cases. , Though perovskite quantum dots are highly luminescent in nature, the stability of these structures is often threatened due to their hydrophobicity, fragility against moisture, and easily strayed halide atoms . Encapsulating perovskite solids with polymer matrices, various inorganic salts, zeolite-Y, and forming core–shell structures are efficient ways to enhance water, thermal, and light stability.…”

“…19,20 Though perovskite quantum dots are highly luminescent in nature, the stability of these structures is often threatened due to their hydrophobicity, fragility against moisture, and easily strayed halide atoms. 6 Encapsulating perovskite solids with polymer matrices, 21 various inorganic salts, 22 zeolite-Y, 10 and forming core−shell structures are efficient ways to enhance water, thermal, and light stability. Qingyun He et al reported a novel strategy by coating halide perovskites on polyvinyl butyral (PVB) and forming an HPSs@PVB composite membrane which was applied in backlight displays owing to its excellent optical properties, flexibility, high water, and thermal stability.…”

“…The magnificent optical propertiesessentially, long carrier diffusion length, tunable band gap, defect tolerance capability, high quantum yield, efficient photoluminescence (PL), and tunable emission over a broad spectrum of all cesium lead halide perovskites have marked its applicability and pertinence in optoelectronic applications, for instance, light emitting diodes (LEDs), solar cells, photodetectors, color converters lasers, and others. − The general formula for perovskites can be depicted as ABX 3 , where A is a monovalent cation such as Cs + , CH 3 NH 3 + , B is any divalent metal, normally Pb 2+ , Sb 2+ , Sn 2+ , and X is a halogen anion (X = Cl, Br, I). − All cesium lead bromide perovskites have acquired considerable attention all over owing to their aforementioned properties and facile synthesis procedure . Based on how the [PbX 6 ] 4– [X = Cl, Br, I] octahedra are connected, they can form different structures including corner shared octahedra (for 3D), layered networks (2D), long chains­(1D), and isolated dots (0D). , It is well evident that each of these crystalline structures exhibits versatile physical and chemical properties …”