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. 2021 Jan 21;6(2):581–587. doi: 10.1021/acsenergylett.0c02448

Exploiting the Lability of Metal Halide Perovskites for Doping Semiconductor Nanocomposites

Mariano Calcabrini †, Aziz Genç ‡,§, Yu Liu †, Tobias Kleinhanns †, Seungho Lee †, Dmitry N Dirin ∥,⊥, Quinten A Akkerman ∥,⊥, Maksym V Kovalenko ∥,⊥, Jordi Arbiol ‡,#, Maria Ibáñez †,*
PMCID: PMC7887873  PMID: 33614964

Abstract

graphic file with name nz0c02448_0006.jpg

Cesium lead halides have intrinsically unstable crystal lattices and easily transform within perovskite and nonperovskite structures. In this work, we explore the conversion of the perovskite CsPbBr3 into Cs4PbBr6 in the presence of PbS at 450 °C to produce doped nanocrystal-based composites with embedded Cs4PbBr6 nanoprecipitates. We show that PbBr2 is extracted from CsPbBr3 and diffuses into the PbS lattice with a consequent increase in the concentration of free charge carriers. This new doping strategy enables the adjustment of the density of charge carriers between 1019 and 1020 cm–3, and it may serve as a general strategy for doping other nanocrystal-based semiconductors.

Research on metal halide perovskites is advancing rapidly, owing to the compelling electronic, optical and structural properties of these ionic semiconductors, such as long diffusion lengths and carrier lifetimes,1−3 low exciton binding energies,4 low number of trap states despite the high concentration of vacancies,1,5 composition-tunable bandgap,6,7 and ease of processability.8−11 Because of the relatively labile crystal structure of metal halide perovskites, the understanding and control of the chemical and structural transformations that these compounds readily undergo are some of the most pressing questions.12

Cesium lead halides can adopt perovskite and nonperovskite structures with different dimensionalities. Perovskites are composed of Cs+ cations stabilizing [PbX6]4– octahedra in a cubic or, upon slight distortion, tetragonal or orthorhombic phases, where all the corners of the [PbX6]4– octahedra are shared.13 All these compounds adopt regular CsPbX3 stoichiometry (3D). Nonperovskite structures include polymorphs with various stoichiometries, but all of them lose the corner-sharing motif in the lattice. The first example of these structures is a polymorph that despite having the same CsPbX3 stoichiometry crystallizes in an orthorhombic phase (δ-phase) with chains of edge-sharing octahedra (1D).14 Another example is the lead-depleted Cs4PbX6 structure where the [PbX6]4– octahedra are isolated (0D).13,15−17 A third closely related nonperovskite structure that has lower Cs+ content and does not contain [PbX6]4– octahedra, CsPb2X5, can be described as layers (2D) of [Pb2X5] ® clusters separated by Cs+ ions.13,15−17 Because of the large difference in the involved atoms’ electronegativities, all these cesium lead halides exhibit mixed bonding nature. The lead halide framework is dominated by covalent bonds and balanced by ionically bound Cs+ cations. The lack of covalency between Cs+ and the anionic units enables crystal lability.18 As a direct consequence, the ions move easily and allow transformation between the different structures—provided that the stoichiometry is compensated.

Very common are the transformations between CsPbBr3 and Cs4PbBr6 structures especially in nanocrystals (NCs). The transformation of Cs4PbBr6 into CsPbBr3 is achieved by adding PbBr2 to the structure,19 extracting CsBr by chemical complexation or intercalation,20 or diffusion and dissolution of CsBr in water.21 The chemical transformation from CsPbBr3 to Cs4PbBr6 can be induced by removing PbBr2 from the crystal lattice by its complexation with thiols or amines.22−24 In all these reactions purification of the NCs is required to separate the undesired byproducts: either CsBr or PbBr2.

PbS NC-based solids find application in various fields including transistors,25−28 solar cells,29−32 photodetectors,31,33,34 and thermoelectrics.35−37 In most of these applications adjusting the number of free charge carriers to control charge transport is crucial. The conventional n-type dopants for bulk lead chalcogenides are halides. Incorporation of halide ions (X= Cl–, Br–, I–) in the chalcogenide (Y= S2–, Se2–, Te2–) sublattice results in the addition of one electron in the conduction band per halide to compensate for the different valency of halides and chalcogenides.38 Strategies to dope bulk semiconductors require control over the composition at the impurity level; the straightforward translation into doping bottom-up assembled NC solids is to use doped NCs. However, impurity doping of NCs is energetically39 and kinetically unfavorable, because the diffusion path of impurity atoms to the surface is short.40 Although tuning NCs composition has been attempted,26,41 the introduction of a controlled amount of impurities in small structures is problematic for the preparation of heavily doped semiconductors.42−44 Alternative approaches to dope NC-based solids have focused on changing the NC surface chemistry,30,36,38,45−48 inducing partial cation exchange,49,50 and blending with other NCs.35,51,52

PbY–perovskite nanocomposites have been used in photodetectors,53,54 LEDs,55,56 and photovoltaics.57,58 Remarkably, PbS NC inclusions can provide stability to the cubic phase of perovskites suppressing the cubic–orthorhombic phase transition,59 and perovskite passivation layers enhance charge carrier separation in PbS NCs by providing adequate energy alignment.60 Furthermore, PbY nanocomposites with secondary phases might be of great importance for thermoelectrics.35,61

Herein we propose a strategy to produce doped PbS nanocomposites that makes use of the byproduct of the transformation of CsPbBr3 into Cs4PbBr6 and PbBr2, upon heating a mixture of CsPbBr3 and PbS NCs (Scheme 1). Our approach simultaneously introduces dopant ions (Br ®) and a secondary phase (Cs4PbBr6) in PbS nanocomposites (Figure 1).

Scheme 1. Chemical Transformation of CsPbBr3 into Cs4PbBr6 Triggered by the Dissolution of PbBr2 in PbS.

Scheme 1

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Figure 1.

Figure 1

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TEM images of the used NCs and scheme of the bottom-up assembly process to produce doped PbS–Cs4PbBr6 nanocomposites. The nanocomposites are prepared by blending the NCs in solution, annealing the dried NCs at 450 °C to remove the organic ligands and induce the chemical transformation between CsPbBr3 and Cs4PbBr6, and finally pressing the annealed powder at 45 MPa and 500 °C for 5 min to produce the pellets.

We prepared nanocomposites by mixing PbS NCs with a controlled amount of CsPbBr3 NCs in toluene. This NCs blend was dried under vacuum and annealed with forming gas (5% H2 in N2, 1 bar) to yield a powder that was then pressed into pellets with relative densities of ∼92% (Table S1) using spark plasma sintering (Figure 1).

To follow the chemical transformation of the perovskites, we performed in situ temperature-dependent X-ray diffraction (XRD) measurements of a mixture of PbS NCs and 30% wt. CsPbBr3 NCs (Figures 2 and S1). This mixture was heated to 450 °C and kept at that temperature for 60 min, mimicking the annealing step. Upon heating to 150 °C, CsPbBr3 NCs show strong sharpening of the reflections explained by accelerated ion migration between particles causing grain growth.62−64 After reaching 450 °C, CsPbBr3 reflections progressively lose intensity, and peaks corresponding to Cs4PbBr6 become visible, shifted to lower angles because of thermal expansion of the lattice. This experiment demonstrates that CsPbBr3 converts to Cs4PbBr6, necessarily releasing PbBr2. This reaction could be enhanced by the binding affinity of PbBr2 to PbS surface dangling bonds.65,66 Control experiments with CsPbBr3 and Cs4PbBr6 pure phases showed that both phases are recovered after heating to 500 °C and cooling to room temperature and do not undergo any transformation on their own (Figures S9 and S10). Besides, annealing induces crystal grain growth in pure PbS NCs, evidenced by the narrowing of the XRD reflections and scanning electron microscopy (SEM) images (Figures S2 and S5). The addition of CsPbBr3 enhances the growth of the PbS crystal domains leading to even narrower reflections (Figures S3 and S4 and Tables S3 and S4). This enhancement can be explained by the presence of PbBr2, a phase with high solubility in PbS67 and a large difference in melting point, which lowers the activation energy for diffusion.68−70 Because no reflections associated with PbBr2 are visible, we considered the possibility of other phases in the PbS–PbBr2 phase diagram being formed. Still, Pb7S2Br10, the only stable phase, was not observed in the diffraction patterns.67 Recently, the metastable phase Pb4S3Br2 was reported in NCs; this phase is not present in the XRD patterns, and we disregarded it because of the high temperature and long reaction time, which are not compatible with such a kinetically stabilized phase.71 Previous studies showed pure CsPbBr3 NCs undergo partial transformation to the lead-rich CsPb2Br5; this phase is not present in our experiments.64 These observations suggest that bromide substitutes sulfide in PbS, doping the matrix as expressed in the chemical reactions in Scheme 1.

Figure 2.

Figure 2

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X-ray diffraction patterns of a mixture of PbS NCs and CsPbBr3 NCs at different temperatures together with the reference patterns for the different crystal phases. In the 450 °C patterns, t indicates the time held at 450 °C before measurement. The patterns are overlapped with a 2D intensity plot to help to identify low intensity reflections (PbS PDF 00-002-0699, CsPbBr3 PDF 00-054-0753, Cs4PbBr6 PDF 01-075-0412).

To test the doping efficiency, we prepared pellets with the proper nominal CsPbBr3 concentrations to achieve charge carrier concentrations between 1019 and 1020 cm–3, which is close to the optimal charge carrier concentration for thermoelectrics.72,73 The molar amount of Br introduced is referred to the amount of S, X% = 0.25, 0.50, 1, 2, 3 (see the Supporting Information, page S1).

Panels a and b of Figure 3 show the electrical conductivity and Seebeck coefficient of the samples between room temperature and 900 K, respectively. At low temperatures, the absolute value of the Seebeck coefficient decreases and the electrical conductivity increases with the starting concentration of CsPbBr3, proving the doping effect of the transformation (Supporting Information, page S8).72 Besides, the negative sign of the Seebeck coefficient confirms the n-type character of the obtained nanocomposites. These results are consistent with the charge carrier concentrations measured by Hall effect (Table S2), which correspond exactly to one-half of the total Br concentration, as expected from the reaction in Scheme 1. The doping effect of CsPbBr3 is independent of the use of NCs; ground perovskite crystals react with PbS in the same way. However, NCs provide a much shorter ion diffusion path and better mixing with PbS, which lead to faster kinetics (Supporting Information, page S10).

Figure 3.

Figure 3

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(a) Electrical conductivity and (b) Seebeck coefficient of the nanocomposites with increasing starting CsPbBr3 concentration: 0% (black squares), 0.25% (red circles), 0.5% (blue triangles), 1% (purple triangles), 2% (green triangles), and 3% (dark blue triangles).

The observed tendencies in the electrical conductivity of nanostructured materials are a trade-off between many effects. On the one hand, the thermal excitation of carriers through energy barriers (grain boundaries) leads to an increase of the conductivity with temperature. This effect dominates at low temperatures in samples with smaller grains. On the other hand, an increase in temperature enhances charge carrier scattering. This is the typical behavior of heavily doped semiconductors and metals. Additionally, as the temperature increases, thermal excitation of minority carriers (bipolar effect) occurs. Consequently, the absolute value of the Seebeck coefficient starts decreasing. The higher the doping level, the higher the temperature at which this effect is perceptible.61

The XRD patterns of the produced pellets show neither CsPbBr3 nor Cs4PbBr6 reflections (Figure S6), which we associate with the low content of perovskite required for the doping level targeted. To demonstrate that the pelletized material contains Cs4PbBr6, we evaluated the microscopic structure of the bulk nanocomposites (Figure 4) by high-resolution transmission electron microscopy (HRTEM). A 0.5% pellet was thinned to electron transparency by Ar+ polishing to produce a self-suspended lamella. Figure 4d shows an HRTEM micrograph obtained from a large PbS grain (defined as the matrix) containing multiple precipitates. The power spectrum of the highlighted area shows diffraction spots of the matrix and the precipitates, along with satellite spots of the Moiré fringes, which are formed because of orientation differences between the matrix and precipitates. Inverse Fourier (frequency) filtering of the power spectrum allowed mapping the matrix and the nanodomains. The matrix phase (in red) is identified as FCC PbS (space group Fm3̅m) with a lattice parameter a = 0.5936 nm visualized along its [011] axis. The nanodomain (in green) corresponds to the same PbS phase visualized along the [001] zone axis. We performed the same analysis on the precipitate marked in Figure 4e. The diffraction spots observed in the power spectrum correspond to the matrix phase (in red) visualized along its [011] axis. The spots of the precipitate correspond to the hexagonal Cs4PbBr6 phase (space group R3̅c:H) with lattice parameters a = 1.373 nm and c = 1.732 nm, which is visualized along the [11̅02] zone axis. Because of the difficulty in analyzing all the precipitates crystallographically, to evaluate their nature we performed energy dispersion X-ray line scans across many precipitates. We found that they show no difference in composition with the matrix (Figure S7), proving that the vast majority of precipitates are PbS. The scans also show a small content of Br evenly distributed through the nanocomposites as expected in its role as a dopant. In short, HRTEM revealed that the doped samples are composed of a PbS matrix with a large amount of PbS nanodomains and randomly distributed Cs4PbBr6 nanoprecipitates (Figure 4), confirming the chemical transformation observed by XRD.

Figure 4.

Figure 4

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Structural analysis of a PbS–Cs4PbBr6 nanocomposite. The TEM sample is a self-suspended lamella prepared by Ar+ ion milling. (a) Photograph of the pellets used to measure the electrical conductivity and the Seebeck coefficient; (b) HRTEM micrograph and (c) low-magnification high-angle annular dark field scanning transmission microscopy (HAADF-STEM) micrograph revealing the presence of small precipitates along the grains; (d) PbS nanodomains, detail of the white squared area and its corresponding power spectrum and structural maps of the PbS matrix (in red) and nanodomains (in green) along with the applied maps for inverse Fourier filtering; (e) detail of a Cs4PbBr6 nanoprecipitate and its corresponding power spectrum and structural maps of the PbS matrix (in red) and a Cs4PbBr6 precipitate (in green) are shown along with the applied maps for inverse Fourier filtering.

In summary, we showed that CsPbBr3 and PbS react to give the lead depleted Cs4PbBr6 phase. The byproduct of the transformation, PbBr2, dissolves in the PbS matrix, leading to doped nanocomposites and inducing grain growth while Cs4PbBr6 forms nanoprecipitates. We made use of this transformation to simultaneously dope and introduce a secondary phase in n-type PbS nanocomposites. These results validate this new doping strategy for nanocomposites based on NC blending that involves the reaction of one of the components. This approach is not limited to the preparation of bulk samples at high pressures but could also be applied to the preparation of films or other nanocomposites because the reaction that leads to doping is also demonstrated at ambient pressure. Finally, our results reassess the intrinsic instability of metal halide perovskites and are therefore of high relevance for applications where these materials are exposed to high energy densities.

Acknowledgments

M.C. has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie Grant Agreement No. 665385. ICN2 acknowledges funding from Generalitat de Catalunya 2017 SGR 327. ICN2 is supported by the Severo Ochoa program from Spanish MINECO (Grant No. SEV-2017-0706) and is funded by the CERCA Programme/Generalitat de Catalunya. This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 823717 – ESTEEM3. M.V.K. acknowledges the support by the European Research Council under the Horizon 2020 Framework Program (ERC Consolidator Grant SCALE-HALO Grant Agreement No. 819740) and by FET-OPEN project no. 862656 (DROP-IT).

Supporting Information Available

The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsenergylett.0c02448.

  • Chemicals, syntheses and preparation of the pellets. Details on the structural characterization and transport measurements (PDF)

The authors declare no competing financial interest.

Supplementary Material

nz0c02448_si_001.pdf (2.1MB, pdf)

References

  1. Shi D.; Adinolfi V.; Comin R.; Yuan M.; Alarousu E.; Buin A.; Chen Y.; Hoogland S.; Rothenberger A.; Katsiev K.; Losovyj Y.; Zhang X.; Dowben P. A.; Mohammed O. F.; Sargent E. H.; Bakr O. M. Low Trap-State Density and Long Carrier Diffusion in Organolead Trihalide Perovskite Single Crystals. Science 2015, 347 (6221), 519–522. 10.1126/science.aaa2725. [DOI] [PubMed] [Google Scholar]
  2. Maculan G.; Sheikh A. D.; Abdelhady A. L.; Saidaminov M. I.; Haque M. A.; Murali B.; Alarousu E.; Mohammed O. F.; Wu T.; Bakr O. M. CH3NH3PbCl3 Single Crystals: Inverse Temperature Crystallization and Visible-Blind UV-Photodetector. J. Phys. Chem. Lett. 2015, 6 (19), 3781–3786. 10.1021/acs.jpclett.5b01666. [DOI] [PubMed] [Google Scholar]
  3. Saidaminov M. I.; Abdelhady A. L.; Murali B.; Alarousu E.; Burlakov V. M.; Peng W.; Dursun I.; Wang L.; He Y.; MacUlan G.; Goriely A.; Wu T.; Mohammed O. F.; Bakr O. M. High-Quality Bulk Hybrid Perovskite Single Crystals within Minutes by Inverse Temperature Crystallization. Nat. Commun. 2015, 6 (1), 7586. 10.1038/ncomms8586. [DOI] [PMC free article] [PubMed] [Google Scholar]
  4. Manser J. S.; Christians J. A.; Kamat P. V. Intriguing Optoelectronic Properties of Metal Halide Perovskites. Chem. Rev. 2016, 116 (21), 12956–13008. 10.1021/acs.chemrev.6b00136. [DOI] [PubMed] [Google Scholar]
  5. Fang H. H.; Adjokatse S.; Wei H.; Yang J.; Blake G. R.; Huang J.; Even J.; Loi M. A. Ultrahigh Sensitivity of Methylammonium Lead Tribromide Perovskite Single Crystals to Environmental Gases. Sci. Adv. 2016, 2 (7), e1600534. 10.1126/sciadv.1600534. [DOI] [PMC free article] [PubMed] [Google Scholar]
  6. Sutton R. J.; Eperon G. E.; Miranda L.; Parrott E. S.; Kamino B. A.; Patel J. B.; Hörantner M. T.; Johnston M. B.; Haghighirad A. A.; Moore D. T.; Snaith H. J. Bandgap-Tunable Cesium Lead Halide Perovskites with High Thermal Stability for Efficient Solar Cells. Adv. Energy Mater. 2016, 6 (8), 1502458. 10.1002/aenm.201502458. [DOI] [Google Scholar]
  7. McMeekin D. P.; Sadoughi G.; Rehman W.; Eperon G. E.; Saliba M.; Hörantner M. T.; Haghighirad A.; Sakai N.; Korte L.; Rech B.; Johnston M. B.; Herz L. M.; Snaith H. J. A Mixed-Cation Lead Mixed-Halide Perovskite Absorber for Tandem Solar Cells. Science 2016, 351 (6269), 151–155. 10.1126/science.aad5845. [DOI] [PubMed] [Google Scholar]
  8. Liu X. K.; Xu W.; Bai S.; Jin Y.; Wang J.; Friend R. H.; Gao F. Metal Halide Perovskites for Light-Emitting Diodes. Nat. Mater. 2021, 20, 10–21. 10.1038/s41563-020-0784-7. [DOI] [PubMed] [Google Scholar]
  9. Noculak A.; Noculak A.; Morad V.; Morad V.; McCall K. M.; Yakunin S.; Shynkarenko Y.; Yakunin S.; Shynkarenko Y.; Wörle M.; Kovalenko M. V. Bright Blue and Green Luminescence of Sb(III) in Double Perovskite Cs2MInCl6 (M = Na, K) Matrices. Chem. Mater. 2020, 32 (12), 5118–5124. 10.1021/acs.chemmater.0c01004. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Jena A. K.; Kulkarni A.; Miyasaka T. Halide Perovskite Photovoltaics: Background, Status, and Future Prospects. Chem. Rev. 2019, 119 (5), 3036–3103. 10.1021/acs.chemrev.8b00539. [DOI] [PubMed] [Google Scholar]
  11. Brenner P.; Bar-On O.; Jakoby M.; Allegro I.; Richards B. S.; Paetzold U. W.; Howard I. A.; Scheuer J.; Lemmer U. Continuous Wave Amplified Spontaneous Emission in Phase-Stable Lead Halide Perovskites. Nat. Commun. 2019, 10 (1), 1–7. 10.1109/CLEOE-EQEC.2019.8871688. [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. Akkerman Q. A.; Rainò G.; Kovalenko M. V.; Manna L. Genesis, Challenges and Opportunities for Colloidal Lead Halide Perovskite Nanocrystals. Nat. Mater. 2018, 17 (5), 394–405. 10.1038/s41563-018-0018-4. [DOI] [PubMed] [Google Scholar]
  13. Bertolotti F.; Protesescu L.; Kovalenko M. V.; Yakunin S.; Cervellino A.; Billinge S. J. L.; Terban M. W.; Pedersen J. S.; Masciocchi N.; Guagliardi A. Coherent Nanotwins and Dynamic Disorder in Cesium Lead Halide Perovskite Nanocrystals. ACS Nano 2017, 11 (4), 3819–3831. 10.1021/acsnano.7b00017. [DOI] [PMC free article] [PubMed] [Google Scholar]
  14. Aebli M.; Benin B. M.; McCall K. M.; Morad V.; Thöny D.; Grützmacher H.; Kovalenko M. V. White CsPbBr3: Characterizing the One-Dimensional Cesium Lead Bromide Polymorph. Helv. Chim. Acta 2020, 103 (7), e2000080. 10.1002/hlca.202000080. [DOI] [Google Scholar]
  15. Piveteau L.; Aebli M.; Yazdani N.; Millen M.; Korosec L.; Krieg F.; Benin B. M.; Morad V.; Piveteau C.; Shiroka T.; Comas-Vives A.; Copéret C.; Lindenberg A. M.; Wood V.; Verel R.; Kovalenko M. V. Bulk and Nanocrystalline Cesium Lead-Halide Perovskites as Seen by Halide Magnetic Resonance. ACS Cent. Sci. 2020, 6 (7), 1138–1149. 10.1021/acscentsci.0c00587. [DOI] [PMC free article] [PubMed] [Google Scholar]
  16. Yin J.; Maity P.; De Bastiani M.; Dursun I.; Bakr O. M.; Brédas J. L.; Mohammed O. F. Molecular Behavior of Zero-Dimensional Perovskites. Sci. Adv. 2017, 3 (12), e1701793. 10.1126/sciadv.1701793. [DOI] [PMC free article] [PubMed] [Google Scholar]
  17. Akkerman Q. A.; Manna L. What Defines a Halide Perovskite?. ACS Energy Lett. 2020, 5 (2), 604–610. 10.1021/acsenergylett.0c00039. [DOI] [PMC free article] [PubMed] [Google Scholar]
  18. Kovalenko M. V.; Protesescu L.; Bodnarchuk M. I. Properties and Potential Optoelectronic Applications of Lead Halide Perovskite Nanocrystals. Science 2017, 358 (6364), 745–750. 10.1126/science.aam7093. [DOI] [PubMed] [Google Scholar]
  19. Li Y.; Huang H.; Xiong Y.; Kershaw S. V.; Rogach A. L. Reversible Transformation between CsPbBr3 and Cs4PbBr6 Nanocrystals. CrystEngComm 2018, 20 (34), 4900–4904. 10.1039/C8CE00911B. [DOI] [Google Scholar]
  20. Palazon F.; Urso C.; De Trizio L.; Akkerman Q.; Marras S.; Locardi F.; Nelli I.; Ferretti M.; Prato M.; Manna L. Postsynthesis Transformation of Insulating Cs4PbBr6 Nanocrystals into Bright Perovskite CsPbBr3 through Physical and Chemical Extraction of CsBr. ACS Energy Lett. 2017, 2 (10), 2445–2448. 10.1021/acsenergylett.7b00842. [DOI] [PMC free article] [PubMed] [Google Scholar]
  21. Wu L.; Hu H.; Xu Y.; Jiang S.; Chen M.; Zhong Q.; Yang D.; Liu Q.; Zhao Y.; Sun B.; Zhang Q.; Yin Y. From Nonluminescent Cs4PbX6 (X = Cl, Br, I) Nanocrystals to Highly Luminescent CsPbX3 Nanocrystals: Water-Triggered Transformation through a CsX-Stripping Mechanism. Nano Lett. 2017, 17 (9), 5799–5804. 10.1021/acs.nanolett.7b02896. [DOI] [PubMed] [Google Scholar]
  22. Palazon F.; Almeida G.; Akkerman Q. A.; De Trizio L.; Dang Z.; Prato M.; Manna L. Changing the Dimensionality of Cesium Lead Bromide Nanocrystals by Reversible Postsynthesis Transformations with Amines. Chem. Mater. 2017, 29 (10), 4167–4171. 10.1021/acs.chemmater.7b00895. [DOI] [PMC free article] [PubMed] [Google Scholar]
  23. Liu Z.; Bekenstein Y.; Ye X.; Nguyen S. C.; Swabeck J.; Zhang D.; Lee S. T.; Yang P.; Ma W.; Alivisatos A. P. Ligand Mediated Transformation of Cesium Lead Bromide Perovskite Nanocrystals to Lead Depleted Cs4PbBr6 Nanocrystals. J. Am. Chem. Soc. 2017, 139 (15), 5309–5312. 10.1021/jacs.7b01409. [DOI] [PubMed] [Google Scholar]
  24. Zhang X.; Wu X.; Liu X.; Chen G.; Wang Y.; Bao J.; Xu X.; Liu X.; Zhang Q.; Yu K.; Wei W.; Liu J.; Xu J.; Jiang H.; Wang P.; Wang X. Heterostructural CsPbX3-PbS (X = Cl, Br, I) Quantum Dots with Tunable Vis-NIR Dual Emission. J. Am. Chem. Soc. 2020, 142 (9), 4464–4471. 10.1021/jacs.9b13681. [DOI] [PubMed] [Google Scholar]
  25. Miranti R.; Shin D.; Septianto R. D.; Ibáñez M.; Kovalenko M. V.; Matsushita N.; Iwasa Y.; Bisri S. Z. Exclusive Electron Transport in Core@Shell PbTe@PbS Colloidal Semiconductor Nanocrystal Assemblies. ACS Nano 2020, 14 (3), 3242–3250. 10.1021/acsnano.9b08687. [DOI] [PubMed] [Google Scholar]
  26. Balazs D. M.; Bijlsma K. I.; Fang H.-H. H.; Dirin D. N.; Döbeli M.; Kovalenko M. V.; Loi M. A. Stoichiometric Control of the Density of States in PbS Colloidal Quantum Dot Solids. Sci. Adv. 2017, 3 (9), eaao1558. 10.1126/sciadv.aao1558. [DOI] [PMC free article] [PubMed] [Google Scholar]
  27. Gilmore R. H.; Lee E. M. Y.; Weidman M. C.; Willard A. P.; Tisdale W. A. Charge Carrier Hopping Dynamics in Homogeneously Broadened PbS Quantum Dot Solids. Nano Lett. 2017, 17 (2), 893–901. 10.1021/acs.nanolett.6b04201. [DOI] [PubMed] [Google Scholar]
  28. Shulga A. G.; Kahmann S.; Dirin D. N.; Graf A.; Zaumseil J.; Kovalenko M. V.; Loi M. A. Electroluminescence Generation in PbS Quantum Dot Light-Emitting Field-Effect Transistors with Solid-State Gating. ACS Nano 2018, 12 (12), 12805–12813. 10.1021/acsnano.8b07938. [DOI] [PMC free article] [PubMed] [Google Scholar]
  29. Speirs M. J.; Balazs D. M.; Dirin D. N.; Kovalenko M. V.; Loi M. A. Increased Efficiency in Pn-Junction PbS QD Solar Cells via NaHS Treatment of the p-Type Layer. Appl. Phys. Lett. 2017, 110 (10), 103904. 10.1063/1.4978444. [DOI] [Google Scholar]
  30. Stavrinadis A.; Pradhan S.; Papagiorgis P.; Itskos G.; Konstantatos G. Suppressing Deep Traps in PbS Colloidal Quantum Dots via Facile Iodide Substitutional Doping for Solar Cells with Efficiency > 10%. ACS Energy Lett. 2017, 2 (4), 739–744. 10.1021/acsenergylett.7b00091. [DOI] [Google Scholar]
  31. Wang Y.; Liu Z.; Huo N.; Li F.; Gu M.; Ling X.; Zhang Y.; Lu K.; Han L.; Fang H.; Shulga A. G.; Xue Y.; Zhou S.; Yang F.; Tang X.; Zheng J.; Antonietta Loi M.; Konstantatos G.; Ma W. Room-Temperature Direct Synthesis of Semi-Conductive PbS Nanocrystal Inks for Optoelectronic Applications. Nat. Commun. 2019, 10 (1), 5136. 10.1038/s41467-019-13158-6. [DOI] [PMC free article] [PubMed] [Google Scholar]
  32. Nienhaus L.; Wu M.; Geva N.; Shepherd J. J.; Wilson M. W. B.; Bulović V.; Van Voorhis T.; Baldo M. A.; Bawendi M. G. Speed Limit for Triplet-Exciton Transfer in Solid-State PbS Nanocrystal-Sensitized Photon Upconversion. ACS Nano 2017, 11 (8), 7848. 10.1021/acsnano.7b02024. [DOI] [PubMed] [Google Scholar]
  33. Saran R.; Curry R. J. Lead Sulphide Nanocrystal Photodetector Technologies. Nat. Photonics 2016, 10 (2), 81–92. 10.1038/nphoton.2015.280. [DOI] [Google Scholar]
  34. Tang H.; Zhong J.; Chen W.; Shi K.; Mei G.; Zhang Y.; Wen Z.; Müller-Buschbaum P.; Wu D.; Wang K.; Sun X. W. Lead Sulfide Quantum Dot Photodetector with Enhanced Responsivity through a Two-Step Ligand-Exchange Method. ACS Appl. Nano Mater. 2019, 2 (10), 6135–6143. 10.1021/acsanm.9b00889. [DOI] [Google Scholar]
  35. Ibáñez M.; Luo Z.; Genç A.; Piveteau L.; Ortega S.; Cadavid D.; Dobrozhan O.; Liu Y.; Nachtegaal M.; Zebarjadi M.; Arbiol J.; Kovalenko M. V.; Cabot A. High-Performance Thermoelectric Nanocomposites from Nanocrystal Building Blocks. Nat. Commun. 2016, 7 (1), 10766. 10.1038/ncomms10766. [DOI] [PMC free article] [PubMed] [Google Scholar]
  36. Ibáñez M.; Korkosz R. J.; Luo Z.; Riba P.; Cadavid D.; Ortega S.; Cabot A.; Kanatzidis M. G. Electron Doping in Bottom-up Engineered Thermoelectric Nanomaterials through HCl-Mediated Ligand Displacement. J. Am. Chem. Soc. 2015, 137 (12), 4046–4049. 10.1021/jacs.5b00091. [DOI] [PubMed] [Google Scholar]
  37. Xu B.; Feng T.; Li Z.; Pantelides S. T.; Wu Y. Constructing Highly Porous Thermoelectric Monoliths with High-Performance and Improved Portability from Solution-Synthesized Shape-Controlled Nanocrystals. Nano Lett. 2018, 18 (6), 4034–4039. 10.1021/acs.nanolett.8b01691. [DOI] [PubMed] [Google Scholar]
  38. Ibáñez M.; Hasler R.; Liu Y.; Dobrozhan O.; Nazarenko O.; Cadavid D.; Cabot A.; Kovalenko M. V. Tuning P-Type Transport in Bottom-Up-Engineered Nanocrystalline Pb Chalcogenides Using Alkali Metal Chalcogenides as Capping Ligands. Chem. Mater. 2017, 29 (17), 7093–7097. 10.1021/acs.chemmater.7b02967. [DOI] [PMC free article] [PubMed] [Google Scholar]
  39. Dalpian G. M.; Chelikowsky J. R. Self-Purification in Semiconductor Nanocrystals. Phys. Rev. Lett. 2006, 96 (22), 226802. 10.1103/PhysRevLett.96.226802. [DOI] [PubMed] [Google Scholar]
  40. Norris D. J.; Efros A. L.; Erwin S. C. Doped Nanocrystals. Science 2008, 319 (5871), 1776–1779. 10.1126/science.1143802. [DOI] [PubMed] [Google Scholar]
  41. Oh S. J.; Berry N. E.; Choi J.-H. H.; Gaulding E. A.; Paik T.; Hong S.-H. H.; Murray C. B.; Kagan C. R. Stoichiometric Control of Lead Chalcogenide Nanocrystal Solids to Enhance Their Electronic and Optoelectronic Device Performance. ACS Nano 2013, 7 (3), 2413–2421. 10.1021/nn3057356. [DOI] [PubMed] [Google Scholar]
  42. Buonsanti R.; Milliron D. J. Chemistry of Doped Colloidal Nanocrystals. Chem. Mater. 2013, 25 (8), 1305–1317. 10.1021/cm304104m. [DOI] [Google Scholar]
  43. Du M. H.; Erwin S. C.; Efros A. L. Trapped-Dopant Model of Doping in Semiconductor Nanocrystals. Nano Lett. 2008, 8 (9), 2878–2882. 10.1021/nl8016169. [DOI] [PubMed] [Google Scholar]
  44. Yazdani N.; Andermatt S.; Yarema M.; Farto V.; Bani-Hashemian M. H.; Volk S.; Lin W. M. M.; Yarema O.; Luisier M.; Wood V. Charge Transport in Semiconductors Assembled from Nanocrystal Quantum Dots. Nat. Commun. 2020, 11 (1), 2852. 10.1038/s41467-020-16560-7. [DOI] [PMC free article] [PubMed] [Google Scholar]
  45. Ning Z.; Voznyy O.; Pan J.; Hoogland S.; Adinolfi V.; Xu J.; Li M.; Kirmani A. R.; Sun J. P.; Minor J.; Kemp K. W.; Dong H.; Rollny L.; Labelle A.; Carey G.; Sutherland B.; Hill I.; Amassian A.; Liu H.; Tang J.; Bakr O. M.; Sargent E. H. Air-Stable n-Type Colloidal Quantum Dot Solids. Nat. Mater. 2014, 13 (8), 822–828. 10.1038/nmat4007. [DOI] [PubMed] [Google Scholar]
  46. Nugraha M. I.; Kumagai S.; Watanabe S.; Sytnyk M.; Heiss W.; Loi M. A.; Takeya J. Enabling Ambipolar to Heavy N-Type Transport in PbS Quantum Dot Solids through Doping with Organic Molecules. ACS Appl. Mater. Interfaces 2017, 9 (21), 18039–18045. 10.1021/acsami.7b02867. [DOI] [PMC free article] [PubMed] [Google Scholar]
  47. Robin A.; Livache C.; Ithurria S.; Lacaze E.; Dubertret B.; Lhuillier E. Surface Control of Doping in Self-Doped Nanocrystals. ACS Appl. Mater. Interfaces 2016, 8 (40), 27122–27128. 10.1021/acsami.6b09530. [DOI] [PubMed] [Google Scholar]
  48. Choi M. J.; García de Arquer F. P.; Proppe A. H.; Seifitokaldani A.; Choi J.; Kim J.; Baek S. W.; Liu M.; Sun B.; Biondi M.; Scheffel B.; Walters G.; Nam D. H.; Jo J. W.; Ouellette O.; Voznyy O.; Hoogland S.; Kelley S. O.; Jung Y. S.; Sargent E. H. Cascade Surface Modification of Colloidal Quantum Dot Inks Enables Efficient Bulk Homojunction Photovoltaics. Nat. Commun. 2020, 11 (1), 103. 10.1038/s41467-019-13437-2. [DOI] [PMC free article] [PubMed] [Google Scholar]
  49. Wang H.; Butler D. J.; Straus D. B.; Oh N.; Wu F.; Guo J.; Xue K.; Lee J. D.; Murray C. B.; Kagan C. R. Air-Stable CuInSe2 Nanocrystal Transistors and Circuits via Post-Deposition Cation Exchange. ACS Nano 2019, 13 (2), 2324–2333. 10.1021/acsnano.8b09055. [DOI] [PubMed] [Google Scholar]
  50. Chakraborty P.; Jin Y.; Barrows C. J.; Dunham S. T.; Gamelin D. R. Kinetics of Isovalent (Cd2+) and Aliovalent (In3+) Cation Exchange in Cd1-xMnxSe Nanocrystals. J. Am. Chem. Soc. 2016, 138 (39), 12885–12893. 10.1021/jacs.6b05949. [DOI] [PubMed] [Google Scholar]
  51. Liu Y.; Cadavid D.; Ibáñez M.; Ortega S.; Martí-Sánchez S.; Dobrozhan O.; Kovalenko M. V.; Arbiol J.; Cabot A. Thermoelectric Properties of Semiconductor-Metal Composites Produced by Particle Blending. APL Mater. 2016, 4 (10), 104813. 10.1063/1.4961679. [DOI] [Google Scholar]
  52. Urban J. J.; Talapin D. V.; Shevchenko E. V.; Kagan C. R.; Murray C. B. Synergism in Binary Nanocrystal Superlattices Leads to Enhanced P-Type Conductivity in Self-Assembled PbTe/Ag2Te Thin Films. Nat. Mater. 2007, 6 (2), 115–121. 10.1038/nmat1826. [DOI] [PubMed] [Google Scholar]
  53. Zhao D.; Huang J.; Qin R.; Yang G.; Yu J. Perovskite Photodetectors: Efficient Visible–Near-Infrared Hybrid Perovskite:PbS Quantum Dot Photodetectors Fabricated Using an Antisolvent Additive Solution Process. Adv. Opt. Mater. 2018, 6 (23), 1870090. 10.1002/adom.201870090. [DOI] [Google Scholar]
  54. Liu C.; Peng H.; Wang K.; Wei C.; Wang Z.; Gong X. PbS Quantum Dots-Induced Trap-Assisted Charge Injection in Perovskite Photodetectors. Nano Energy 2016, 30, 27–35. 10.1016/j.nanoen.2016.09.035. [DOI] [Google Scholar]
  55. Piatkowski P.; Masi S.; Galar P.; Gutiérrez M.; Ngo T. T.; Mora-Seró I.; Douhal A. Deciphering the Role of Quantum Dot Size in the Ultrafast Charge Carrier Dynamics at the Perovskite-Quantum Dot Interface. J. Mater. Chem. C 2020, 8 (42), 14834–14844. 10.1039/D0TC03835K. [DOI] [Google Scholar]
  56. Gong X.; Yang Z.; Walters G.; Comin R.; Ning Z.; Beauregard E.; Adinolfi V.; Voznyy O.; Sargent E. H. Highly Efficient Quantum Dot Near-Infrared Light-Emitting Diodes. Nat. Photonics 2016, 10 (4), 253–257. 10.1038/nphoton.2016.11. [DOI] [Google Scholar]
  57. Ning Z.; Gong X.; Comin R.; Walters G.; Fan F.; Voznyy O.; Yassitepe E.; Buin A.; Hoogland S.; Sargent E. H. Quantum-Dot-in-Perovskite Solids. Nature 2015, 523 (7560), 324–328. 10.1038/nature14563. [DOI] [PubMed] [Google Scholar]
  58. Yang Z.; Janmohamed A.; Lan X.; García De Arquer F. P.; Voznyy O.; Yassitepe E.; Kim G.-H.; Ning Z.; Gong X.; Comin R.; Sargent E. H. Colloidal Quantum Dot Photovoltaics Enhanced by Perovskite Shelling. Nano Lett. 2015, 15, 7539. 10.1021/acs.nanolett.5b03271. [DOI] [PubMed] [Google Scholar]
  59. Liu M.; Chen Y.; Tan C. S.; Quintero-Bermudez R.; Proppe A. H.; Munir R.; Tan H.; Voznyy O.; Scheffel B.; Walters G.; Kam A. P. T.; Sun B.; Choi M. J.; Hoogland S.; Amassian A.; Kelley S. O.; García de Arquer F. P.; Sargent E. H. Lattice Anchoring Stabilizes Solution-Processed Semiconductors. Nature 2019, 570 (7759), 96–101. 10.1038/s41586-019-1239-7. [DOI] [PubMed] [Google Scholar]
  60. Sytnyk M.; Yakunin S.; Schöfberger W.; Lechner R. T.; Burian M.; Ludescher L.; Killilea N. A.; Yousefiamin A.; Kriegner D.; Stangl J.; Groiss H.; Heiss W. Quasi-Epitaxial Metal-Halide Perovskite Ligand Shells on PbS Nanocrystals. ACS Nano 2017, 11 (2), 1246–1256. 10.1021/acsnano.6b04721. [DOI] [PubMed] [Google Scholar]
  61. Wang H.; Schechtel E.; Pei Y.; Snyder G. J. High Thermoelectric Effinciency of N-Type PbS. Adv. Energy Mater. 2013, 3 (4), 488–495. 10.1002/aenm.201200683. [DOI] [Google Scholar]
  62. Zhang Q.; Wang B.; Zheng W.; Kong L.; Wan Q.; Zhang C.; Li Z.; Cao X.; Liu M.; Li L. Ceramic-like Stable CsPbBr3 Nanocrystals Encapsulated in Silica Derived from Molecular Sieve Templates. Nat. Commun. 2020, 11 (1), 31. 10.1038/s41467-019-13881-0. [DOI] [PMC free article] [PubMed] [Google Scholar]
  63. Palazon F.; Di Stasio F.; Lauciello S.; Krahne R.; Prato M.; Manna L. Evolution of CsPbBr3 Nanocrystals upon Post-Synthesis Annealing under an Inert Atmosphere. J. Mater. Chem. C 2016, 4 (39), 9179–9182. 10.1039/C6TC03342C. [DOI] [Google Scholar]
  64. Palazon F.; Dogan S.; Marras S.; Locardi F.; Nelli I.; Rastogi P.; Ferretti M.; Prato M.; Krahne R.; Manna L. From CsPbBr3 Nano-Inks to Sintered CsPbBr3-CsPb2Br5 Films via Thermal Annealing: Implications on Optoelectronic Properties. J. Phys. Chem. C 2017, 121 (21), 11956–11961. 10.1021/acs.jpcc.7b03389. [DOI] [PMC free article] [PubMed] [Google Scholar]
  65. Tang J.; Kemp K. W.; Hoogland S.; Jeong K. S.; Liu H.; Levina L.; Furukawa M.; Wang X.; Debnath R.; Cha D.; Chou K. W.; Fischer A.; Amassian A.; Asbury J. B.; Sargent E. H. Colloidal-Quantum-Dot Photovoltaics Using Atomic-Ligand Passivation. Nat. Mater. 2011, 10 (10), 765–771. 10.1038/nmat3118. [DOI] [PubMed] [Google Scholar]
  66. Tang J.; Brzozowski L.; Barkhouse D. A. R.; Wang X.; Debnath R.; Wolowiec R.; Palmiano E.; Levina L.; Pattantyus-Abraham A. G.; Jamakosmanovic D.; Sargent E. H. Quantum Dot Photovoltaics in the Extreme Quantum Confinement Regime: The Surface-Chemical Origins of Exceptional Air- and Light-Stability. ACS Nano 2010, 4 (2), 869–878. 10.1021/nn901564q. [DOI] [PubMed] [Google Scholar]
  67. Rabenau A.; Rau H. Über Sulfidhalogenide Des Bleis Und Das Pb4SeBr6. Z. Anorg. Allg. Chem. 1969, 369 (3–6), 295–305. 10.1002/zaac.19693690319. [DOI] [Google Scholar]
  68. German R. M.; Rabin B. H. Enhanced Sintering through Second Phase Additions. Powder Metall. 1985, 28 (1), 7–12. 10.1179/pom.1985.28.1.7. [DOI] [Google Scholar]
  69. Zovas P. E.; German R. M.; Hwang K. S.; Li C. J. Activated and Liquid-Phase Sintering—Progress and Problems. J. Met. 1983, 35 (1), 28–33. 10.1007/BF03338181. [DOI] [Google Scholar]
  70. Zhang H.; Dasbiswas K.; Ludwig N. B.; Han G.; Lee B.; Vaikuntanathan S.; Talapin D. V. Stable Colloids in Molten Inorganic Salts. Nature 2017, 542 (7641), 328–331. 10.1038/nature21041. [DOI] [PubMed] [Google Scholar]
  71. Toso S.; Akkerman Q. A.; Martín-García B.; Prato M.; Zito J.; Infante I.; Dang Z.; Moliterni A.; Giannini C.; Bladt E.; Lobato I.; Ramade J.; Bals S.; Buha J.; Spirito D.; Mugnaioli E.; Gemmi M.; Manna L. Nanocrystals of Lead Chalcohalides: A Series of Kinetically Trapped Metastable Nanostructures. J. Am. Chem. Soc. 2020, 142 (22), 10198–10211. 10.1021/jacs.0c03577. [DOI] [PMC free article] [PubMed] [Google Scholar]
  72. Snyder G. J.; Toberer E. S. Complex Thermoelectric Materials. Nat. Mater. 2008, 7 (2), 105–114. 10.1038/nmat2090. [DOI] [PubMed] [Google Scholar]
  73. Ortega S.; Ibáñez M.; Liu Y.; Zhang Y.; Kovalenko M. V.; Cadavid D.; Cabot A. Bottom-up Engineering of Thermoelectric Nanomaterials and Devices from Solution-Processed Nanoparticle Building Blocks. Chem. Soc. Rev. 2017, 46 (12), 3510–3528. 10.1039/C6CS00567E. [DOI] [PubMed] [Google Scholar]

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