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Perovskite Quantum Dots


Product Code M2124A1
Price $60.00 ex. VAT

High purity, high PLQY Perovskite Quantum Dots

Caesium lead perovskite quantum dots of chloride/bromide, bromide, and iodide available from £45.00


Perovskite quantum dots are semiconducting nanocrystals. Compared to metal chalcogenide quantum dots, perovskite quantum dots are more tolerant to defects and have excellent photoluminescence quantum yields and high colour purity. These properties are highly desirable for electronic and optoelectronic applications and hence perovskite quantum dots have huge potential for real world applications including LED displays and quantum dot solar cells.

Caesium lead perovskite quantum dots of chloride/bromide (450 nm, blue), bromide (520-530 nm nm, green) and iodide (685 nm, red) are now available.

Full spectrum perovskite quantum dots
Full spectrum range of perovskite quantum dots coming soon
Perovskite Quantum Dot Photoluminescence Spectra
The photoluminescence emission wavelength can be tuned by varying the ratio of halides present within the quantum dot, by careful selection the emission can be varied from 400 nm to 700 nm - measurable with an optical spectrometer (see spectrometer application notes)

What is a Perovskite Quantum Dot?


A new class of quantum dot is emerging based on perovskites. These have already been shown to have properties rivalling or exceeding those of metal chalcogenide QDs.

Due to their outstanding photovoltaic performance, perovskites are receiving significant attention from the research community. Recently, has been shown that reducing the dimensions of a perovskite crystal down to a few nanometres results in the creation of quantum dots with very high photoluminescence quantum yields and excellent colour purity (i.e. narrow emission linewidths of ~10 nm for blue emitters and 40 nm for red emitters [1]).

These quantum dots are highly tolerant to defects, as they require no passivation of the surface to retain their high PLQY. Although defect and trap sites are present, their energies are positioned outside the bandgap and are either located within the conduction or valence bands [2]. Such perovskite nanocrystals are simple to synthesise in a colloidal suspension and are easily integrated into optoelectronic devices using readily available processing techniques, making them a strong contender for future technologies.

Applications of Perovskite Quantum Dots

Perovskite quantum dots have huge potential for a range of applications in electronics, optoelectronics and nanotechnology. Currently, the field is not well researched, but initial results are extremely promising. Details on a selection of the applications that have been investigated are given below.

Quantum Dot Solar Cells

Currently, reports of perovskite quantum dot solar cells are still limited, especially when compared to bulk and 2-dimensional perovskites. This is likely due to the limited time that such materials have been available. However, recent results  suggest that perovskite quantum dots could play a role in future photovoltaic devices.

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Light-Emitting Diodes (LEDs)

Metal chalcogenide quantum dots already play a role in consumer display products - so the increased PLQY, ease of synthesis, excellent colour purity, and wide colour tunability of perovskite quantum dots suggest that they should be well-suited to such applications. However, charge injection and transport in nanocrystal films must be optimised in order to achieve high-efficiency devices.

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Lasers

Amplified spontaneous emission (ASE) has been observed in drop cast films of CsPbBr3, and mixed CsPb(Br/I)3 and CsPb(Cl/Br)3 nanocrystals. Pump thresholds can be as low as 5 µJ cm-2 [13]; a value that compares very favourably with other colloidal QD systems (e.g. an order of magnitude lower than spectrally similar CdSe QDs). The ASE emission intensity is extremely stable in air, dropping by only 10% after several hours of irradiation and ~107 shots in ambient conditions. This performance also compares extremely well to chalcogenide QDs [14]. The stimulated emission has been identified as resulting from the recombination of biexcitons (which are more stable at room temperature than excitons), with red-shifted emission leading to reduced self-absorption (and hence low lasing thresholds). The ASE wavelength can also be tuned throughout the entire visible spectrum via mixing the halide composition.

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Singler Photo Sources

Single photon sources are required for new light-based quantum information systems. Here, current efforts mainly focus on the use of epitaxially-grown quantum dots, diamond colour centers and colloidal nanocrystals. Of these, colloidal NCs are the most promising for room-temperature visible operation [20].

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Photodetectors

The high absorption coefficient of perovskite QDs over a wide spectral range may make them suitable candidates for use in light-detection devices. Pan et al. have reported the fabrication of a phototransistor based on FAPbBr3 quantum dots and graphene [22]. The QDs which act as the light absorber, are deposited onto a monolayer of graphene that transports photoexcited charges to the source/drain. Such phototransistors have a broad response spanning the visible spectrum, although they have reduced response to photons having energies below the semiconductor bandgap (540 nm). Here, a photoresponsivity of 1.15×105 AW-1 was observed at 520 nm; a value that is amongst the highest of any graphene-based photodetectors.

Perovskite Quantum Dot Structure

Halide perovskite nanocrystals have a cubic crystal structure with the chemical formula A+Pb2+X-3. They can be classed as an organic-inorganic hybrid, where A is an organic cation such as methylammonium (MA) or formamidinium (FA), or fully inorganic (A=Cs), and where X is a halogen (Cl, Br or I). Due to the lack of volatile organics, fully-inorganic nanocrystals tend to have better stability and higher PLQY (>90%) than hybrid organic-inorganic materials [3]. Mixed halide perovskites can also be produced where X is a mixture of Cl/Br or Br/I.

For visible optoelectronic applications, the nanocrystals are generally synthesised to have a size of 4 - 15 nm (dependent on the halogen atom and the required optical properties). The emission wavelength can be tuned through the entire visible spectrum (400 - 700nm [4]) by changing either the nanocrystal size or halide ratio (for mixed halide systems).

Perovskite quantum dot structure
Figure 1: Lead halide perovskite quantum dots have a cubic structure and are often synthesised with organic ligands.

Perovskite Quantum Dot Synthesis

The first hybrid organic-inorganic perovskite quantum dot colloidal synthesis of MAPbBr3 was reported by Schmidt et al. using a hot injection method (similar to that used to synthesise metal chalcogenide QDs [4]). A mixture of methylamine bromide and lead bromide was injected into an octadecene solution containing oleic acid and a long chain alkyl ammonium bromide. The PLQY of the resulting QDs was ~20%, and was stable for several months due to the stabilising and capping effects of the ammonium bromide and oleic acid. By optimisation of the reactant molar ratios, the PLQY was increased to over 80% [5], and later to ~100% by changing the capping ligand [6].

Perovskite quantum dot ink synthesis
Figure 2: The synthesis of perovskite quantum dots involves injecting Cs-oleate into a lead precursor.

Hot injection was again used for the colloidal synthesis of inorganic metal-halide perovskite quantum dots, first reported by Protesescu et al [1]. That recipe developed was as follows:

  1. The caesium precursor Cs-oleate is first prepared by mixing caesium carbonate (Cs2CO3) and oleic acid (OA) in octadecene (ODE), and heating under nitrogen until the Cs2CO3 has reacted with the OA. This solution must be kept above 100°C to prevent precipitation of the Cs-oleate.
  2. A lead halide precursor is prepared by mixing a lead halide (PbCl2, PbI2, PbBr2 or a mixture of these) in ODE at 120°C under nitrogen, along with OA and oleylamine (OLA) that act as stabilising agents. Once the lead halide has dissolved, the temperature is increased to between 140-200°C (depending on the required nanocrystal size).
  3. The caesium precursor is then injected. After 5 seconds, the mixture is rapidly cooled in an ice bath, with the quantum dots being isolated through centrifuging.

The resulting nanocrystals have surface ligands comprised of OA and OLA [3]. Such nanocrystals were found to have PLQYs up to ~90%, with the smallest crystals (4 nm diameter) having an emission linewidth (full width half maximum) of 12 nm at an emission wavelength of 410 nm, with the largest quantum dots (15 nm diameter) having a linewidth of 42 nm at 700 nm.

Video by Ossila

During the production process the reaction mixture is quenched by cooling in an ice-water bath.

Mixed-Halide Perovskite Quantum Dots

An advantage that perovskite quantum dots have over their metal chalcogenide counterparts is the simplicity by which their emission properties can be modified. In addition to tuning the emission wavelength during synthesis through reaction temperature (and ultimately, nanocrystal size), it can also be changed post-synthesis through an anion-exchange reaction [7,8]. By mixing a donor halide source such as octadecylammonium (ODA-Y), chloro-oleyalmine-oleylammonium chloride (OLAM-Y) or tetrabutylammonium (TBA-Y) halide (where Y is Cl, Br or I) with a solution of CsPbX3 nanocrystals, the chemical composition of the nanocrystals can be tuned continuously over the range CsPb(X1-Z:YZ), where 0≤Z≤1.

Anion exchange in perovskite quantum dots
A possible mechanism for anion exchange in perovskite quantum dots.

Anion exchange is followed by lattice reconfiguration, giving a mixed halide structure. This results in a single emission peak at an energy somewhere in between those of the constituent nanocrystals, thereby retaining the narrow linewidth needed for color purity. However it has been found that direct conversion between CsPbI3 and CsPbCl3 is not possible because of the large mismatch in the size of the halide ions.

It has also been demonstrated that this anion exchange process can be easily accomplished by simply mixing different stock solutions of the nanocrystal constituents at different volume ratios (e.g. CsPbBr3 and CsPbI3 to obtain CsPb(Br1-Z:IZ)3 [7,9]). Both methods allow the nanocrystal emission to be tuned over the entire visible range while retaining a high PLQY and color purity. The anion exchange process can however be suppressed by adding polyhedral oligomeric silsesquioxane (POSS) to the solution. This creates a protective cage around the nanocrystals, and allows mixing of different halide compositions while retaining the photoluminescent properties of the constituent nanocrystals. It also has the added effect of protecting the nanocrystals from water [10].

Perovskite quantum dot ink
Figure 3: A CsPbBr perovskite quantum dot ink under normal illumination (left) and ultraviolet illumination (right).

Literature

References

Technical Data

CsPbBr3 Perovskite Quantum Dots

CAS Number 15243-48-8
Chemical Formula CsPbBr3
Molecular Weight 579.82 g/mol
Full Name Caesium lead tribromide quantum dots
Synonyms Caesium lead bromide quantum dots
Classification / Family Perovskite quantum dots, Perovskite nanocrystal solutions, Cadmium-free quantum dots, Quantum dot solutions, Green emitter, Quantum dot LEDs (QDLEDs), Perovskite LEDs (PeLEDs), Perovskite solar cells (PvSCs)
Purity 99%
Appearance Yellow Liquid
Emission Peak 520-530 nm
Emission Linewidth (FWHM) 21 nm
Photoluminescence Quantum Yield ~77%

CsPbCl1.5Br1.5 Perovskite Quantum Dots

CAS Number Not available
Chemical Formula CsPbCl1.5Br1.5
Molecular Weight 513.14 g/mol
Full Name Caesium lead chloride bromide quantum dots
Synonyms Caesium lead chloride bromide quantum dots
Classification / Family Perovskite quantum dots, Perovskite nanocrystal solutions, Cadmium-free quantum dots, Quantum dot solutions, Green emitter, Quantum dot LEDs (QDLEDs), Perovskite LEDs (PeLEDs), Perovskite solar cells (PvSCs)
Purity 99%
Appearance Clear Liquid
Emission Peak 450 nm
Emission Linewidth (FWHM) 20 nm
Photoluminescence Quantum Yield 30 - 40%

CsPbI3 Perovskite Quantum Dots

CAS Number 18041-25-3
Chemical Formula CsPbI3
Molecular Weight 720.82 g/mol
Full Name Caesium lead triiodide quantum dots
Synonyms Caesium lead iodide quantum dots
Classification / Family Perovskite quantum dots, Perovskite nanocrystal solutions, Cadmium-free quantum dots, Quantum dot solutions, Green emitter, Quantum dot LEDs (QDLEDs), Perovskite LEDs (PeLEDs), Perovskite solar cells (PvSCs)
Purity 99%
Appearance Dark Red Liquid
Emission Peak 688 nm
Emission Linewidth (FWHM) 39 nm
Photoluminescence Quantum Yield 60 - 70%

Perovskite Quantum Dot Spectral Data

CsPbBr3 Perovskite Quantum Dots Absorption SpectraCsPbBr3 Perovskite Quantum Dots Absorption Spectra

CsPbBr3 Perovskite Quantum Dots Photoluminescence SpectraCsPbBr3 Perovskite Quantum Dots Photoluminescence Spectra

CsPbCl1.5Br1.5 Perovskite Quantum Dots Photoluminescence SpectraCsPbCl1.5Br1.5 Perovskite Quantum Dots Photoluminescence Spectra

CsPbI3 Perovskite Quantum Dots Photoluminescence SpectraCsPbI3 Perovskite Quantum Dots Photoluminescence Spectra

MSDS Documents

Toluene Dispersed CsPbBr3 Perovskite Quantum Dots MSDSCsPbBr3 Perovskite Quantum Dots in Toluene

Octane Dispersed CsPbBr3 Perovskite Quantum Dots MSDSCsPbBr3 Perovskite Quantum Dots in Octane

Pricing Table

Perovskite Solvent Concentration Volume Product Code Price
CsPbX3 Toluene 10 mg.ml-1 1 ml M2124 £45.00
CsPbX3 Toluene 10 mg.ml-1 5 ml M2124 £200.00
CsPbX3 Toluene 10 mg.ml-1 10 ml M2124 £350.00
CsPbX3 Toluene 10 mg.ml-1 25 ml M2124 £700.00
CsPbX3 Octane 10 mg.ml-1 1 ml M2124 £45.00
CsPbX3 Octane 10 mg.ml-1 5 ml M2124 £200.00
CsPbBr3 Octane 10 mg.ml-1 10 ml M2124 £350.00
CsPbX3 Octane 10 mg.ml-1 25 ml M2124 £700.00

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To the best of our knowledge the information provided here is accurate. However, Ossila assume no liability for the accuracy of this page. The values provided are typical at the time of manufacture and may vary over time and from batch to batch. All products are for laboratory and research and development use only, and may not be used for any other purpose including health care, pharmaceuticals, cosmetics, food or commercial applications.

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