Technical Data

CsPbBr₃ Perovskite Quantum Dots

CsPbCl_1.5Br_1.5 Perovskite Quantum Dots

CsPbI₃ Perovskite Quantum Dots

Perovskite Quantum Dot Spectral Data

CsPbBr₃ Perovskite Quantum Dots Absorption Spectra

CsPbBr₃ Perovskite Quantum Dots Photoluminescence Spectra

CsPbCl_1.5Br_1.5 Perovskite Quantum Dots Photoluminescence Spectra

CsPbI₃ Perovskite Quantum Dots Photoluminescence Spectra

MSDS Documents

CsPbBr₃ Perovskite Quantum Dots in Toluene

CsPbBr₃ Perovskite Quantum Dots in Octane

Properties of Perovskite Quantum Dots

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 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].

 

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.

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(X_1-Z:Y_Z), where 0≤Z≤1.

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(Br_1-Z:I_Z)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].

 

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.

Pricing Table

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Literature

References

1. Nanocrystals of Cesium Lead Halide Perovskites (CsPbX₃, X = Cl, Br, and I): Novel Optoelectronic Materials Showing Bright Emission with Wide Color Gamut, L. Protesescu et al., Nano Lett., 15 (6), 3692–3696 (2015)
2. Lead Halide Perovskite Nanocrystals in the Research Spotlight: Stability and Defect Tolerance, Huang et al., ACS Energy Lett., 2 (9), 2071–2083 (2017)
3. 50‐Fold EQE Improvement up to 6.27% of Solution‐Processed All‐Inorganic Perovskite CsPbBr₃ QLEDs via Surface Ligand Density Control, Li et al., Adv. Mater., 29 (5), 1603885 (2017)
4. Nontemplate Synthesis of CH₃NH₃PbBr₃ Perovskite Nanoparticles, L. Schmidt et al., Am. Chem. Soc., 136 (3), 850–853 (2014)
5. Maximizing the emissive properties of CH₃NH₃PbBr₃ perovskite nanoparticles, S. Gonzalex-Carrero et al., J. Mater. Chem. A, 3, 9187-9193 (2015)
6. The Luminescence of CH₃NH₃PbBr₃ Perovskite Nanoparticles Crests the Summit and Their Photostability under Wet Conditions is Enhanced, Gonzalex-Carrero et al., Small, 12 (38), 5245-5250 (2016)
7. Fast Anion-Exchange in Highly Luminescent Nanocrystals of Cesium Lead Halide Perovskites (CsPbX₃, X = Cl, Br, I), N. Nedelcu et al., Nano Lett., 15 (8), 5635–5640 (2015)
8. Tuning the Optical Properties of Cesium Lead Halide Perovskite Nanocrystals by Anion Exchange Reactions, Akkerman et al., J. Am. Chem. Soc., 137 (32), 10276–10281 (2015)
9. Room-Temperature Construction of Mixed-Halide Perovskite Quantum Dots with High Photoluminescence Quantum Yield, C. Bi et al., J. Phys. Chem. C, 122 (9), 5151–5160 (2018)
10. Water resistant CsPbX₃ nanocrystals coated with polyhedral oligomeric silsesquioxane and their use as solid state luminophores in all-perovskite white light-emitting devices, H. Huang et al., Chem Sci., 7 (9), 5699–5703 (2016)
11. Quantum dot light-emitting diodes based on inorganic perovskite cesium lead halides (CsPbX₃), J. Song et al., Adv. Mater., 27, 7162-7167 (2015)
12. Perovskite Crystals for Tunable White Light Emission, S. Pathak et al., Chem. Mater., 27 (23), 8066–8075 (2015)
13. Low-threshold amplified spontaneous emission and lasing from colloidal nanocrystals of caesium lead halide perovskites, S. Yakunin et al., Nat. Comm., 6, 8056 (2015)
14. All‐Inorganic Colloidal Perovskite Quantum Dots: A New Class of Lasing Materials with Favorable Characteristics, Y. Wang et al., Adv. Mater., 27 (44), 7101-7108 (2015)
15. Nonlinear Absorption and Low-Threshold Multiphoton Pumped Stimulated Emission from All-Inorganic Perovskite Nanocrystals, Wang et al., Nano Lett., 16 (1), 448–453 (2016)
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19. Perovskite Quantum Dots: A New Absorber for Perovskite-Perovskite Tandem Solar Cells: Preprint, J. Christians et al., National Renewable Energy Laboratory. NREL/CP-5900-71593 (2018)
20. Superior Optical Properties of Perovskite Nanocrystals as Single Photon Emitters, F. Hu et al., ACS Nano, 9 (12), 12410–12416 (2015)
21. Room Temperature Single-Photon Emission from Individual Perovskite Quantum Dots, YS. Park et al., ACS Nano, 9(10), 10386–10393 (2015)
22. Photodetectors: High‐Responsivity Photodetectors Based on Formamidinium Lead Halide Perovskite Quantum Dot–Graphene Hybrid, R. Pan et al., Particle, 35 (4), 1700304 (2018)