Stabilizing Cesium Lead Halide Perovskite Lattice through Mn (II)- Substitution for Air-Stable Light-Emitting Diodes

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1 Supporting Information Stabilizing Cesium Lead Halide Perovskite Lattice through Mn (II)- Substitution for Air-Stable Light-Emitting Diodes Shenghan Zou,,,,# Yongsheng Liu, *, Jianhai Li, Caiping Liu, Rui Feng, Feilong Jiang, Yongxiang Li, # Jizhong Song, Haibo Zeng, *, Maochun Hong, *, and Xueyuan Chen *, CAS Key Laboratory of Design and Assembly of Functional Nanostructures, CAS Key Laboratory of Optoelectronic Materials Chemistry and Physics, and State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian , China. Institute of Optoelectronics and Nanomaterials, School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing , China Testing Center, Fuzhou University, Fuzhou, Fujian , China University of the Chinese Academy of Sciences, Beijing, , China School of Physical Science and Technology, ShanghaiTech University, Shanghai , China # Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai , China *To whom correspondence should be addressed, liuysh@fjirsm.ac.cn, zeng.haibo@njust.edu.cn, hmc@fjirsm.ac.cn, and xchen@fjirsm.ac.cn Experimental Section Chemicals and Materials. Cesium carbonate (Cs 2 CO 3, 99.9%), lead (II) bromide (PbBr 2, 98%), lead (II) chloride (PbCl 2, %), lead (II) iodide (PbI 2, %), manganese (II) chloride tetrahydrate (MnCl 2 4H 2 O, 99.99%), manganese (II) bromide (MnBr 2, 98%), manganese (II) iodide (MnI 2, 98%), oleic acid (OA, technical grade 90%), oleylamine (OAm, 80-90%), 1-octadecene (ODE, 90%) were purchased from Sigma-Aldrich. Acetone, cyclohexane, N, N-Dimethylformamide (DMF) and ethanol were purchased from Sinopharm Chemical Reagent Co., China. All chemicals were used without purification unless otherwise noted. Preparation of Cs-Oleate Precursor. In a typical procedure, a mixture of 0.4 g Cs 2 CO 3, 1.5 ml OA and 15 ml ODE was added to a 100 ml two-neck flask and degassed under N 2 flow at room temperature for 20 min, and then heated to 150 o C and kept at this temperature under N 2 flow until all Cs 2 CO 3 was dissolved. After cooling to room temperature naturally, the obtained Cs-oleate precursor in ODE was stored in a glovebox under argon protection. S1

2 General Procedure for the Synthesis of CsMnX 3 Nanocrystals (NCs): In brief, mmol MnX 2 (X = Cl, Br, I) was first added to a 50 ml two-neck flask containing 5 ml ODE, 0.5 ml OA and 0.5 ml OAm and degassed under N 2 flow at room temperature for 20 min, and then heated at 120 C under N 2 flow with constant stirring for 60 min to remove the moisture from raw materials. Thereafter, the mixture was heated to 150 C under N 2 flow with constant stirring, followed by a rapid injection of 0.4 ml Cs-oleate precursor abovementioned (0.125 M in ODE). After reacting for 60 min, the reaction mixture was cooled down to room temperature naturally to obtain CsMnX 3 NCs. The obtained CsMnX 3 NCs were collected by centrifugation at rpm for 5 min and stored in a glovebox under argon protection. General Procedure for the Synthesis of CsPbX 3 Quantum Dots (QDs) with Mn 2+ Adsorbed on the Surface: In brief, mmol MnX 2 was first added to a 50 ml two-neck flask containing 5 ml ODE, 0.5 ml OA and 0.5 ml OAm and degassed under N 2 flow at room temperature for 20 min, and then heated at 120 C under N 2 flow with constant stirring for 60 min to remove the moisture from raw materials. Thereafter, the mixture was cooled down to room temperature naturally, followed by a rapid injection of pure CsPbX 3 QDs abovementioned under N 2 flow with constant stirring. After reacting for 24 h, the reaction mixture was centrifugated at rpm for 5 min to obtain CsPbX 3 QDs with Mn 2+ ion adsorbed on their surfaces. S2

3 Supplementary Figures Figure S1. Size distribution for (a) Mn 2+ -doped CsPbCl 3 and (b) pure CsPbCl 3 QDs obtained from typical transmission electron microscopy (TEM) images of 200 QDs. The average size for CsPbCl 3 :Mn QDs was determined be 8.6 ± 0.5 nm, which is slightly larger than their pure counterparts with an average size of 7.9 ± 0.5 nm, indicating that Mn 2+ doping can promote the growth of CsPbX 3 QDs. S3

4 Figure S2. Typical TEM and high-resolution TEM images for (a, b) pure and (c, d) Mn2+-doped CsPbBr3 QDs. It can be seen clearly that both the pure and Mn2+-doped CsPbBr3 QDs have a nearly cubic morphology, and the average sizes for pure and Mn2+-doped CsPbBr3 QDs can be determined to be 8.2 ± 0.5 and 8.7 ± 0.5 nm, respectively. Similar to the case of pure CsPbBr3 QDs, clear lattice fringes ascribed to the (110) facet of orthorhombic perovskite CsPbBr3 crystal were also observed for Mn2+-doped CsPbBr3:Mn QDs, indicating that the crystallinity for CsPbX3:Mn QDs is comparable to their pure counterparts. S4

5 Figure S3. Powder X-ray diffraction (XRD) patterns for as-synthesized (a) CsPbCl 3 :Mn and (b) CsPbBr 3 :Mn QDs doped with different Mn 2+ contents, showing that almost all XRD peaks for CsPbCl 3 :Mn and CsPbBr 3 :Mn QDs can be well indexed in accordance with orthorhombic perovskite structures of CsPbCl 3 (JCPDS No ) and CsPbBr 3 (JCPDS No ) crystals. (c) XRD patterns for as-synthesized CsPbI 3 :Mn QDs doped with different Mn 2+ contents, revealing that almost all the XRD peaks for CsPbI 3 :Mn QDs can be well indexed as a cubic perovskite CsPbI 3 structure (ICSD, No ) as previously reported. 1 Note that high-resolution XRD patterns for CsPbCl 3 :Mn and CsPbBr 3 :Mn QDs are needed to exactly discriminate their orthorhombic crystal structures from the cubic ones, in view of the slight difference in the crystal lattice parameters and standard XRD patterns for orthorhombic and cubic S5

6 perovskite CsPbCl 3 (Cubic phase: a = b = c = 5.60 Å; Orthorhombic phase: a = b = 5.58 Å, c = 5.62 Å) and CsPbBr 3 (Cubic phase: a = b = c = 5.83 Å; Orthorhombic phase: a = b = 5.83 Å, c = 5.89 Å) crystals. As shown in Figure S3a, two adjacent XRD peaks centered at 31.8 o (marked by the star sign) and 32.0 o were detected in the XRD pattern of CsPbCl 3 :Mn QDs we synthesized, which can be readily assigned to the (002) and (200) facets of orthorhombic perovskite CsPbCl 3 crystal structure (JCPDS No ), indicating that the CsPbCl 3 :Mn QDs we synthesized crystallize in the orthorhombic phase instead of cubic phase. For the CsPbBr 3 :Mn QDs doped with different Mn 2+ contents, weak XRD peaks centered at 24.1 o (marked by the pound sign) can be detected in Figure S3b, which is unique for the orthorhombic perovskite CsPbBr 3 crystal but missing in the cubic perovskite CsPbBr 3 crystal, thereby providing solid evidence to confirm the formation of orthorhombic perovskite crystal structure of CsPbBr 3 :Mn QDs we synthesized. As for CsPbI 3 :Mn QDs doped with different Mn 2+ contents, we would like to emphasize that the whole XRD patterns are dominated by the XRD peaks originating from the cubic perovskite CsPbI 3 crystal (ICSD, No ). S6

7 Figure S4. Comparison of photoluminescence (PL) emission spectra for (a) CsPbCl 3 :Mn, (b) CsPbBr 3 :Mn and (c) CsPbI 3 :Mn QDs doped with different Mn 2+ contents. Note that all the PL emission spectra were measured under identical experimental conditions upon a 362-nm UV lamp excitation. All the integrated PL intensities for excitonic luminescence of CsPbCl 3 :Mn, CsPbBr 3 :Mn and CsPbI 3 :Mn QDs were observed to rise first and then decrease with increasing the doping concentration of Mn 2+ ion, which suggests that the Mn 2+ ion has a significant impact on the optical properties of CsPbX 3 :Mn QDs. S7

8 Figure S5. PL decays for (a) Mn 2+ -related and (b) excitonic emissions of CsPbCl 3 :Mn QDs centered at 600 and 404 nm upon 397-nm (or 375-nm) pulsed laser excitation, and their corresponding (c, d) PL lifetimes as a function of the nominal doping content of Mn 2+ ion. Note that the nominal Mn 2+ doping concentration was used herein for clarity. By using a single exponential function fitting, the PL lifetime for Mn 2+ -related emission of CsPbCl 3 :Mn QDs was determined to be about 1.2 ms (c), which is approximately six orders of magnitude longer than that of excitonic emission of CsPbCl 3 :Mn QDs in the range of ns determined from double exponential function fitting (d). Such much prolonged lifetimes clearly demonstrate that the broad emission centered at 600 nm for CsPbCl 3 :Mn QDs indeed originates form Mn 2+ ion doped into the lattice of CsPbCl 3 QDs. S8

9 Figure S6. Absolute PL quantum yields (QYs) for CsPbCl 3 :Mn QDs doped with different nominal Mn 2+ contents ranging from 0 to 80 mol%. Note that the nominal Mn 2+ doping concentration was used herein for clarity. The absolute PL QY was observed to increase markedly from 0.6% for pure QDs to 12.7% for CsPbCl 3 :Mn QDs (60 mol% ) upon 362-nm UV lamp excitation, due to the stepwise increased orange-red luminescence of Mn 2+ centered at 600 nm. S9

10 Figure S7. PL decay curves (left) and lifetimes (right) for excitonic luminescence of CsPbBr 3 :Mn QDs upon excitation by a 397-nm pulsed laser. Note that the nominal Mn 2+ doping concentration was used herein for clarity. All the PL decay curves were fitted by using double exponential function, and the PL lifetime for excitonic luminescence of CsPbBr 3 :Mn QDs was determined to decrease from 20.8 to 6.3 ns with increased nominal Mn 2+ doping concentration. Such step-bystep shortened PL lifetime for CsPbBr 3 :Mn QDs with increased Mn 2+ content is understandable due to the fact the doping of Mn 2+ ion in the lattice of CsPbX 3 QDs can act as an additional nonradiative relaxation channels of the excited CsPbBr 3 QDs and thereby result in the decreased PL lifetime. This result provides another solid evidence to manifest the successful doping of Mn 2+ ion in the lattices of CsPbX 3 QDs particularly for CsPbBr 3 QDs. S10

11 Figure S8. Absolute PL QYs for CsPbBr 3 :Mn and CsPbI 3 :Mn QDs doped with different nominal Mn 2+ contents ranging from 0 to 60 mol%. Note that the nominal Mn 2+ doping concentration was used herein for clarity. The PL QYs for both the CsPbBr 3 :Mn and CsPbI 3 :Mn QDs were observed to increase first and then decrease with increasing the nominal Mn 2+ doping concentration from 0 to 60 mol%, yielding the highest PL QYs of 57.1% and 89.6% for CsPbBr 3 :Mn and CsPbI 3 :Mn QDs at a nominal Mn 2+ doping concentration of 20 mol%, respectively, which are about 1.1 and 1.4 times higher than those of pure CsPbBr 3 (53.3 %) and CsPbI 3 (65.1%) QDs synthesized under otherwise identical experimental conditions, demonstrating that the Mn 2+ ion has a significant impact on the optical properties of CsPbBr 3 :Mn and CsPbI 3 :Mn QDs. S11

12 Figure S9. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) image of single randomly selected CsPbI 3 :Mn (7.9 mol%) QD and its corresponding energy dispersive X-ray spectroscopy (EDS) elemental mapping images of Mn, Cs, Pb and I. It can be seen clearly that Mn 2+ ions are homogeneously distributed among the whole QD, which reveals that Mn 2+ ion can be successfully doped into the lattice of CsPbI 3 QDs. S12

13 Figure S10. Photographs for pure CsPbBr3, CsPbBr3:Mn (2.6 mol%) and CsPbBr3:Mn (4.3 mol%) QDs dispersed in cyclohexane taken at (a) daylight or (b) upon 365-nm UV irradiation. It can be seen clearly that the CsPbBr3:Mn (2.6 mol%) QDs remain essentially unchanged within 40 days, which differs markedly from pure CsPbBr3 and CsPbBr3:Mn (4.3 mol%) QDs that undergo a rapid degradation in term of PL brightness and solution color. These results indicate that the CsPbBr3:Mn QDs with Mn2+ doping content of 2.6 mol% are much more stable than pure CsPbBr3 or CsPbBr3:Mn (4.3 mol%) QDs, in line with our first-principle calculation that shows a decline trend after initial ascent of formation energy with increased Mn2+ doping concentration. S13

14 Figure S11. Typical high-resolution TEM images for (a) CsPbBr 3 :Mn and (b) pure CsPbBr 3 QDs, demonstrating the presence of lattice contractions (marked by dotted blue square) induced by Mn 2+ doping in CsPbBr 3 QDs. It was found that lattice defects or distortions different from their normal lattice arrangement can be occasionally detected in Mn 2+ - doped CsPbBr 3 QDs, while such lattice defects or distortions are hardly detectable in pure CsPbBr 3 QDs. S14

15 Figure S12. Temperature-dependent PL intensities for excitonic luminescence of CsPbI 3 :Mn (7.9 mol%) and pure CsPbI 3 QDs measured under identical experimental conditions via three heating and cooling cycles at 100, 150 and 200 C, respectively. Note that all the samples were first heated from room temperature to high temperature ( C) and then cooled down to room temperature with a temperature interval of 10 C. For the most unstable CsPbI 3 :Mn (7.9 mol%) QDs, their PL intensity can be retained about 20% of their original initial intensity after three heating and cooling cycles at 100, 150 and 200 C. By contrast, the PL emission for pure CsPbI 3 QDs was hardly detectable when heating to 150 C. These results reveal that the CsPbX 3 :Mn QDs possess much better thermal stability than those of pure CsPbX 3 QDs without Mn 2+ ion doping. S15

16 Figure S13. Temperature-dependent PL intensities of Mn 2+ -related emission centered at 600 nm for CsPbCl 3 :Mn (5.8 mol%) QDs via three heating and cooling cycles at 100, 150 and 200 C, respectively. It can be seen clearly that the integrated intensities for Mn 2+ -related emission of CsPbCl 3 :Mn (5.8 mol%) QDs decrease step-by-step after undergoing three heating and cooling cycles at 100, 150 and 200 C, which reveals that excess Mn 2+ ions doped into the lattices of CsPbCl 3 QDs beyond their optimal doping concentration can be gradually excluded from the lattices of perovskite CsPbX 3 QDs when heated at high temperature to yield the most thermodynamically stable ones. S16

17 Figure S14. (a) HAADF-STEM image of one single randomly selected CsPbBr3:Sn (4.3 mol%) QD and (b-f) its corresponding EDS elemental mapping images of Sn, Cs, Pb and Br. It can be seen clearly that Sn2+ ions are homogeneously distributed among the whole QD, indicative of the successful doping of Sn2+ ion in CsPbBr3 QDs. S17

18 Figure S15. Temperature-dependent PL intensities for excitonic luminescence of CsPbBr 3 :Sn QDs with a Sn 2+ ion doping concentration of 4.3 mol% via three heating and cooling cycles at 100, 150 and 200 C, respectively. Note that all the samples were first heated from room temperature to high temperature ( C) and then cooled down to room temperature with a temperature interval of 10 C. It was found that the PL intensity for excitonic luminescence of CsPbBr 3 :Sn QDs was greatly enhanced by a factor of ~1.5 as compared to their initial intensity after three heating and cooling cycles at 100, 150 and 200 C, respectively, which is even better than the increased value of ~1.2 for CsPbBr 3 :Mn QDs undergoing the same heating and cooling cycles. These results unambiguously reconfirm that the much improved thermal stability for CsPbX 3 :Mn 2+ QDs as compared to their pure counterparts indeed originates from the enhanced formation energies of CsPbX 3 QDs. S18

19 Figure S16. Temperature-dependent PL intensities for excitonic luminescence of Cd 2+, Co 2+, Zn 2+ and Sr 2+ doped CsPbBr 3 QDs with a nominal divalent ion doping concentration of 40 mol% via three heating and cooling cycles at 100, 150 and 200 C, respectively. The PL intensities for excitonic luminescence of Cd 2+, Co 2+, Zn 2+ and Sr 2+ doped CsPbBr 3 QDs can be retained about 55%, 75%, 76% and 67% of their original initial intensity after undergoing three heating and cooling cycles at 100, 150 and 200 C, which was quite different from the case of pure CsPbBr 3 QDs whose PL emission degraded to less than 26 % of its original intensity. These experimental results are basically consistent with our theoretical calculations showing that the absolute values for formation energies of Cd 2+, Co 2+, Zn 2+ and Sr 2+ doped CsPbBr 3 QDs are increased as compared to their pure counterparts (Table S5). Taken together, we can deduce that the increased formation energies of CsPbX 3 QDs through such divalent cation doping strategy will certainly improve the thermal stability of CsPbX 3 QDs. Although the absolute values for calculated formation energies of Cd 2+ (-6.84 ev), Co 2+ (-6.81 ev), Zn 2+ (-6.86 ev) and Sr 2+ (-6.84 ev) doped CsPbBr 3 QDs are calculated to be higher than those of CsPbBr 3 :Mn 2+ and CsPbBr 3 :Sn 2+ QDs, their enhanced PL intensities for excitonic luminescence are lower relative to those of CsPbBr 3 :Mn 2+ (~1.2 times) and CsPbBr 3 :Sn 2+ (~1.5 times) QDs. This observation may be caused by the facts that the Cd 2+, Co 2+, Zn 2+ and Sr 2+ ions usually crystallize into different types of crystal structures of Cs 3 CdBr 5 (Space group: I4/mcm), Cs 3 CoBr 5 (Space group: I4/mcm), Cs 2 ZnBr 4 (Space group: I4/mcm) and CsSrBr 3 (Space group: P6 3 /mmc) with different space groups, which S19

20 makes the substitution of Pb 2+ in the lattices of CsPbBr 3 (Space group: Pm-3m) QDs more difficult than Sn 2+ or Mn 2+ ions possessing the same octahedral coordination environment of host cations. As a result, the actual doping concentrations for Ca 2+, Co 2+, Zn 2+ and Sr 2+ doped CsPbBr 3 QDs is much lower than those of CsPbBr 3 :Mn 2+ and CsPbBr 3 :Sn 2+ QDs regardless of their identical nominal doping concentration of 40 mol% (Table S4), thereby resulting in weak excitonic luminescence than those of CsPbBr 3 :Mn 2+ and CsPbBr 3 :Sn 2+ QDs S20

21 Figure S17. Red PL emission photographs for CsPbI 3 :Mn QDs with different nominal Mn 2+ doping concentrations of 0, 20, 40, 50, 60, 80, 100 mol% from left to right respectively, taken at daylight or under UV irradiation at indicated time period. Their red PL brightness can be detected within 3-5 days, which is in stark contrast to the complete degradation of pure CsPbI 3 QDs within 2 days, thereby providing solid evidence that the Mn 2+ dopants also play a very important role in enhancing the air stability of CsPbX 3 QDs. S21

22 Figure S18. (a) Schematic illustration of typical multilayer-structured perovskite light-emitting diode (PLED) device by using pure CsPbI 3, CsPbI 3 :Mn (7.9 mol%) and CsPbI 3 :Mn (21.6 mol%) QDs as red light emitters (hereafter referred to as PLED-pure, PLED-Mn7.9, and PLED-Mn21.6, respectively). (b) Comparison of normalized electroluminescence (EL) spectra at an applied voltage of 6 V and their corresponding PL emission spectra for CsPbI 3, CsPbI 3 :Mn (7.9 mol%) and CsPbI 3 :Mn (21.6 mol%) QDs when dispersed in cyclohexane solution. Current density (c) and luminance (d) versus driving voltage characteristics for PLED-pure, PLED-Mn7.9, and PLED-Mn21.6 devices. (e) External quantum efficiency (EQE) of these devices as a function of luminance. (f) Current efficiency (CE) of these devices as a function of current density. As compared in Figure 6b, all the red-emitting PLED devices produce red EL centered at nm with narrow full-width at half-maximum (FWHM) of ~42 nm, which can be readily attributed to the band-edge emission of CsPbI 3 QDs with only ~5 nm blue shift relative to their PL emission peak acquired from the corresponding QDs, indicating that these PLEDs based on the CsPbI 3 :Mn QDs have inherited the PL color purity of pure CsPbI 3 QDs. Similar to the cases of green-emitting PLEDs we fabricated, much more improved luminance, EQE and CE were also achieved in these PLEDs by using Mn 2+ -doped CsPbI 3 red emitters. For example, the maximum EQE was determined to significantly increase from 0.41% for PLED-pure device to 1.04 % for the PLED-Mn21.6 device. These results further confirm the significant advantages of Mn-doped CsPbX 3 QDs against the undoped counterparts for the fabrication of high-performance optoelectronic devices. Furthermore, we would like to emphasize that all the measurements for the performance of these red-emitting PLED devices were carried out under ambient air conditions without any encapsulation or protection, indicative of the good air-stability of the PLED devices we fabricated. S22

23 Supplementary Tables Table S1. Calculated formation energies ( E form ) for the unit cells of CsPbX 3 (X = Cl, Br, I) and CsMnX 3 crystals by using first-principle calculation based on the density functional theory (DFT). Generally speaking, the larger absolute value of E form, the more stable is the crystal. Crystal CsPbCl 3 CsPbBr 3 CsPbI 3 CsMnCl 3 CsMnBr 3 CsMnI 3 Formation Energy (ev) S23

24 Table S2. Comparison of nominal Mn 2+ doping content and actual Mn 2+ doping content determined from inductively coupled plasma atomic emission spectroscopy (ICP-AES) for Mn 2+ -doped CsPbX 3 QDs. Note that the actual Mn 2+ doping contents were observed to deviate considerably from their nominal ones as previously reported. 2 Sample Nominal Mn 2+ doping content (mol%) Actual Mn 2+ doping content from ICP-AES (mol%) CsPbCl CsPbCl 3 :Mn CsPbCl 3 :Mn CsPbCl 3 :Mn CsPbCl 3 :Mn CsPbCl 3 :Mn CsPbCl 3 :Mn CsPbCl 3 :Mn CsPbCl 3 :Mn CsPbBr CsPbBr 3 :Mn CsPbBr 3 :Mn CsPbBr 3 :Mn CsPbBr 3 :Mn CsPbBr 3 :Mn CsPbBr 3 :Mn CsPbBr 3 :Mn CsPbBr 3 :Mn CsPbI CsPbI 3 :Mn CsPbI 3 :Mn CsPbI 3 :Mn CsPbI 3 :Mn CsPbI 3 :Mn CsPbI 3 :Mn S24

25 Table S3. Calculated bond lengths for perovskite CsPbBr 3 QDs doped with different Mn 2+ contents by using the firstprinciple calculation based on DFT. Crystals Mn / mol% Br-Mn / Å Br-Pb / Å a) Br-Pb / Å b) CsPbBr / / c) Cs 64 Mn 1 Pb 63 Br Cs 48 Mn 1 Pb 47 Br Cs 32 Mn 1 Pb 31 Br Cs 27 Mn 1 Pb 26 Br Cs 18 Mn 1 Pb 17 Br Cs 16 Mn 1 Pb 15 Br Cs 12 Mn 1 Pb 11 Br Cs 10 Mn 1 Pb 9 Br Cs 8 Mn 1 Pb 7 Br Cs 4 Mn 1 Pb 3 Br CsMnBr c) / / a) The average bond lengths of the Br-Pb bonds adjacent to the Br-Mn bonds; b) The average bond lengths of Br-Pb bonds far from Br-Mn bonds; c) The calculated bond lengths for CsMnBr 3 and CsPbBr 3 crystals are well consistent with values of (No. 9703) and (No ) from ICSD database, thereby demonstrating the reliability of our first-principle calculation. S25

26 Table S4. Actual divalent ion doping content determined form ICP-AES for Sn 2+, Cd 2+, Co 2+, Zn 2+ and Sr 2+ doped CsPbBr 3 QDs with a nominal doping content of 40 mol%. Sample Nominal divalent ion doping content (mol%) Actual divalent ion doping content from ICP-AES (mol%) CsPbBr 3 :Sn CsPbBr 3 :Co CsPbBr 3 :Cd CsPbBr 3 :Zn CsPbBr 3 :Sr S26

27 Table S5. Calculated formation energies for cubic perovskite CsPbBr 3 QDs doped with different divalent dopants by using the first-principle calculation based on DFT. Crystal Divalent dopant content (mol%) E form (Per divalent dopant, ev) CsPbBr Cs 48 Mn 1 Pb 47 Br Cs 48 Sn 1 Pb 47 Br Cs 48 Cd 1 Pb 47 Br Cs 48 Co 1 Pb 47 Br Cs 48 Zn 1 Pb 47 Br Cs 48 Sr 1 Pb 47 Br S27

28 Table S6. Summary of the performance of the perovskite-based LEDs. Emitters Structure EL max. (nm) V on (V) Max. EQE (%) Max. CE (cd A -1 ) Max. PE (lm W -1 ) Max. L (Cd m -2 ) CsPbBr 3 QDs CsPbBr 3 :Mn 2.6 mol% QDs CsPbBr 3 :Mn 3.8 mol% QDs CsPbI 3 QDs / 64 CsPbI 3 :Mn 7.9 mol% QDs / 157 CsPbI 3 :Mn 21.6 mol% QDs / 132 CsPbBr 3 QDs CsPbBr 3 QDs / CsPbBr 3 QDs / / CsPbBr 3 QDs CsPbBr 3 Films / / CsPbBr 3 Films / Ref. This work References (1) Swarnkar, A.; Marshall, A. R.; Sanehira, E. M.; Chernomordik, B. D.; Moore, D. T.; Christians, J. A.; Chakrabarti, T.; Luther, J. M. Science 2016, 354, 92. (2) Parobek, D.; Roman, B. J.; Dong, Y.; Jin, H.; Lee, E.; Sheldon, M.; Son, D. H. Nano Lett 2016, 16, (3) Li, J. H.; Xu, L. M.; Wang, T.; Song, J. Z.; Chen, J. W.; Xue, J.; Dong, Y. H.; Cai, B.; Shan, Q. S.; Han, B. N.; Zeng, H. B. Adv. Mater. 2017, 29, (4) Zhang, X.; Lin, H.; Huang, H.; Reckmeier, C.; Zhang, Y.; Choy, W. C. H.; Rogach, A. L. Nano Lett 2016, 16, (5) Li, G.; Rivarola, F. W. R.; Davis, N. J. L. K.; Bai, S.; Jellicoe, T. C.; de la Peña, F.; Hou, S.; Ducati, C.; Gao, F.; Friend, R. H.; Greenham, N. C.; Tan, Z.-K. Adv. Mater. 2016, 28, (6) Zhang, X.; Xu, B.; Zhang, J.; Gao, Y.; Zheng, Y.; Wang, K.; Sun, X. W. Adv. Funct. Mater. 2016, 26, (7) Yantara, N.; Bhaumik, S.; Yan, F.; Sabba, D.; Dewi, H. A.; Mathews, N.; Boix, P. P.; Demir, H. V.; Mhaisalkar, S. J. Phys. Chem. Lett. 2015, 6, (8) Ling, Y.; Tian, Y.; Wang, X.; Wang, J. C.; Knox, J. M.; Perez-Orive, F.; Du, Y.; Tan, L.; Hanson, K.; Ma, B.; Gao, H. Adv. Mater. 2016, 28, S28