Recent progress has been made on the synthesis and characterization of metal halide perovskite magic-sized clusters (PMSCs) with ABX 3 composition ( A = C H 3 N H 3 + or Cs + , B = P b 2 + , and X = C l − , Br - , or I - ). However, their mechanism of growth and structure is still not well understood. In our effort to understand their structure and growth, we discovered that a new species can be formed without the CH 3 NH 3 + component, which we name as molecular clusters (MCs). Specifically, CH 3 NH 3 PbBr 3 PMSCs, with a characteristic absorption peak at 424 nm, are synthesized using PbBr 2 and CH 3 NH 3 Br as precursors and butylamine (BTYA) and valeric acid (VA) as ligands, while MCs, with an absorption peak at 402 nm, are synthesized using solely PbBr 2 and BTYA, without CH 3 NH 3 Br. Interestingly, PMSCs are converted spontaneously overtime into MCs. An isosbestic point in their electronic absorption spectra indicates a direct interplay between the PMSCs and MCs. Therefore, we suggest that the MCs are precursors to the PMSCs. From spectroscopic and extendedmore »
Doping and ion substitution in colloidal metal halide perovskite nanocrystals
The past decade has witnessed tremendous advances in synthesis of metal halide perovskites and their use for a rich variety of optoelectronics applications. Metal halide perovskite has the general formula ABX 3 , where A is a monovalent cation (which can be either organic ( e.g. , CH 3 NH 3 + (MA), CH(NH 2 ) 2 + (FA)) or inorganic ( e.g. , Cs + )), B is a divalent metal cation (usually Pb 2+ ), and X is a halogen anion (Cl − , Br − , I − ). Particularly, the photoluminescence (PL) properties of metal halide perovskites have garnered much attention due to the recent rapid development of perovskite nanocrystals. The introduction of capping ligands enables the synthesis of colloidal perovskite nanocrystals which offer new insight into dimension-dependent physical properties compared to their bulk counterparts. It is notable that doping and ion substitution represent effective strategies for tailoring the optoelectronic properties ( e.g. , absorption band gap, PL emission, and quantum yield (QY)) and stabilities of perovskite nanocrystals. The doping and ion substitution processes can be performed during or after the synthesis of colloidal nanocrystals by incorporating new A′, B′, or X′ site ions into the more »
- Award ID(s):
- 1914713
- Publication Date:
- NSF-PAR ID:
- 10226170
- Journal Name:
- Chemical Society Reviews
- Volume:
- 49
- Issue:
- 14
- Page Range or eLocation-ID:
- 4953 to 5007
- ISSN:
- 0306-0012
- Sponsoring Org:
- National Science Foundation
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All-inorganic lead halide perovskite (CsPbX3) nanocrystals (NCs) have emerged as a highly promising new generation of light emitters due to their extraordinary photophysical properties. However, the performance of these semiconducting NCs is undermined due to the inherent toxicity of lead and long-term environmental stability. Here, we report the addition of B-site cation and X-site anion (pseudo-halide) concurrently using Ba(SCN)2 (≤50%) in CsPbX3 NCs to reduce the lead and improve the photophysical properties and stability. The as-grown particles demonstrated an analogous structure with an almost identical lattice constant and a fluctuation of particle size without altering the morphology of particles. Photoluminescence quantum yield is enhanced up to near unity (~98%) by taking advantage of concomitant doping at the B- and X-site of the structure. Benefitted from the defect reductions and stronger bonding interaction between Pb2+ and SCN− ions, Ba(SCN)2-based NCs exhibit improved stability towards air and moisture compared to the host NCs. The doped NCs retain higher PLQY (as high as seven times) compared to the host NCs) when stored in an ambient atmosphere for more than 176 days. A novel 3D-printed multiplex color conversion layer was used to fabricate a white light-emitting diode (LED). The obtained white light shows amore »
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All-inorganic halide perovskite nanocrystals (NCs) offer impressive optoelectronic properties for light harvesting, energy conversion, and photoredox applications, with two-dimensional (2D) perovskite NCs further increasing these prospects due to their improved photoluminescence (PL) tuneability, impressive color purity, high in-plane charge transport, and large lateral dimensions which is advantageous for device integration. However, the synthesis of 2D perovskites is still challenging, especially toward large-scale applications. In this study, through the control of surface ligand composition and concentration of a mixture of short (octanoic acid and octylamine, 8-carbon chain) and long (oleic acid and oleylamine, 18-carbon chain) ligands, we have developed an extremely facile ligand-mediated synthesis of 2D CsPbX 3 (X = Cl, Br, or mixture thereof) nanoplatelets (NPLs) at room temperature in an open vessel. In addition, the developed method is highly versatile and can be applied to synthesize Mn-doped CsPbX 3 NPLs, showing a systematic increase in the total PL quantum yield (QY) and the Mn-dopant emission around 600 nm with increasing Mn and Cl concentrations. The reaction occurs in toluene by the introduction of CsX, PbX 2 , and MnX 2 precursors under ambient conditions, which requires no harsh acids, avoids excessive lead waste, little thermal energy input, and ismore »
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Control over the nucleation and growth of lead-halide perovskite crystals is critical to obtain semiconductor films with high quantum yields in optoelectronic devices. In this report, we use the change in fluorescence brightness to image the transformation of individual lead bromide (PbBr 2 ) nanocrystals to methylammonium lead bromide (CH 3 NH 3 PbBr 3 ) via intercalation of CH 3 NH 3 Br. Analyzing this reaction one nanocrystal at a time reveals information that is masked when the fluorescence intensity is averaged over many particles. Sharp rises in the intensity of single nanocrystals indicate they transform much faster than the time it takes for the ensemble average to transform. While the ensemble reaction rate increases with increasing CH 3 NH 3 Br concentration, the intensity rises for individual nanocrystals are insensitive to the CH 3 NH 3 Br concentration. To explain these observations, we propose a phase-transformation model in which the reconstructive transitions necessary to convert a PbBr 2 nanocrystal into CH 3 NH 3 PbBr 3 initially create a high energy barrier for ion intercalation. A critical point in the transformation occurs when the crystal adopts the perovskite phase, at which point the activation energy for further ionmore »
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Accepted Manuscript1.0
- Publisher's Version of Record
- https://doi.org/10.1039/C9CS00790C
