Doping Mn2+ in Single-Crystalline Layered Perovskite Microcrystals

Dec 26, 2018 - Doping Mn2+ in Single-Crystalline Layered Perovskite Microcrystals. Sumit Kumar Dutta , Anirban Dutta , Samrat Das Adhikari , and Naray...
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Doping Mn2+ in Single-Crystalline Layered Perovskite Microcrystals Sumit Kumar Dutta, Anirban Dutta, Samrat Das Adhikari, and Narayan Pradhan* School of Materials Science, Indian Association for the Cultivation of Science, Kolkata 700032, India

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S Supporting Information *

ABSTRACT: While solution-processed doping of Mn ions in 3D lead halide perovskites is extensively studied, the chemistry for Mn doping in 2D layered perovskites is limited. Following a generic solution-phase colloidal approach in the presence of alkylammonium salts, formation of single-crystalline microcrystals of Mn-doped layered perovskites (L2PbX4, X = Cl, Br, I) is reported. While Mn was present in all microstructures, only L2PbBr4 led to Mn d−d emission with high quantum yield (∼61%). These doped layered structures showed robust stability and even retained the original emission in continuous thermocycling or constant heating at 200 °C in air for more than 24 h. Moreover, these materials also showed solid-state thermal annealinginduced 2D agglomeration leading to a larger structure, which was reflected from optical microscopic images and the enhanced intensity of powder XRD peaks that originated from the layered structure. Apart from the generic synthesis, these results also provided several new fundamental insights on doping and doped 2D perovskites, which were timely required for the advancement of the materials property and understanding the growth mechanism of these materials.

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rise to strongly bound excitons with high binding energies even at room temperature, which is not present in their 3D analogue.54−56 Hence, the advantage of these perovskites on doping might be efficient exciton energy transfer leading to intense dopant emission. Further, doping these materials would shift the new emission away from the absorption band and thereby minimize the self-absorption of the material, enabling these as ideal materials for LEDs, photovoltaics, and solar concentrator applications.57−59 However, the established doping in layered perovskites was mostly restricted to solid-state synthesis and not widely explored in solution phase.23 A recent report has also shown Mn emission from L2PbBr4 in solution-phase synthesis, but this was used as an intermediate to synthesize Mn-doped CsPbBr3. However, details of the crystal structure or doping in these layered structures were not established.22 Because these have the ability to exhibit intense Mn emission, deeper understanding of the synthetic chemistry to dope these materials and dopant-induced change or evolution of new materials properties need to be explored. Following a generic solution-based synthetic approach, herein, single-crystalline microcrystals of layered L2PbX4 (X = Cl, Br, I) were reported, and these were successfully doped with Mn(II). Doping was monitored through elemental

oping has recently emerged as an efficient approach in inducing new materials properties, bringing stability and also enhancing the charge carrier mobility in perovskite nanocrystals.1−11 Extensive research has been carried out targeting the B site doping of cesium lead halide perovskites, and success has also been widely achieved with Mn2+.7,12−19 However, to obtain efficient dopant emission, CsPbCl3 is targeted as the ideal host, whose band positions remained ideal for its exciton energy transfer to dopant Mn dstates.4,5,11,20,21 In addition, doping in CsPbI3 has been carried out to stabilize the cubic phase of the nanocrystals.6 Beyond these 3D nanocrystals, incorporation of Mn has also been reported for 2D layered perovskites, L2PbBr4 (L = organic spacer ligand), though these were less explored in comparison to 3D CsPbX3.22,23 For 2D layered perovskites, instead of Cs + , larger alkylammonium ions typically occupied the A sites in the APbX3 lattice and acted as spacer ligands between two consecutive inorganic layers.24−36 However, this can only be observed when the chain length of the alkyl ammonium ion consists of greater than 3 carbon units.29,37 Therefore, the twodimensional (2D) layered perovskite, L2PbX4, can be thought of as being derived from a 3D APbX3 lattice by slicing the lattice along a particular plane.26,38−53 Being that only A site bondings were replaced with ammonium ions and B sites remained unaltered, doping could be possible in these B sites of the nanostructures similar to 3D CsPbX3 perovskites.7,12−19 Further, the structural characteristics of 2D perovskites give © XXXX American Chemical Society

Received: December 3, 2018 Accepted: December 26, 2018 Published: December 26, 2018 343

DOI: 10.1021/acsenergylett.8b02349 ACS Energy Lett. 2019, 4, 343−351

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Figure 1. (a−c) PL and PLE spectra of L2PbCl4, L2PbBr4, and L2PbI4 microcrystals, respectively. (d−f) Unit cells obtained from singlecrystal X-ray diffraction (XRD) measurements for L2PbCl4, L2PbBr4, and L2PbI4, respectively. L2PbCl4 was viewed along [001], and L2PbBr4 and L2PbI4 were viewed along [100].

analysis, and the position of the dopant ion was verified by electron paramagnetic resonance (EPR) spectroscopy. While L2PbCl4 was observed to be a high-band-gap material with no luminescence property, L2PbI4 was found to be a low-band-gap semiconductor, but L2PbBr4 was observed to be an ideal host for facilitating the exciton energy transfer-induced Mn d−d emission with an unprecedented quantum yield of ∼61% at room temperature. Apart from this, compared to all Mn-doped quantum dot systems (both chalcogenide and perovskite), the Mn-doped L2PbBr4 was observed to be stable during thermocycling (25−200 °C and then again to 25 °C) and thermal annealing in air. The obtained crystals were characterized both optically and microscopically. Single-crystal X-ray diffraction (XRD) measurements for all of these microcrystals were carried out, and simulated XRD patterns were verified with powder XRD patterns. The adopted organic phase approach remained also generic and the first of its kind for 2D perovskites. Single-crystalline microcrystals of doped and undoped layered perovskite, L2PbX4 (L = butylammonium and X = Cl, Br, and I) were synthesized by loading all of the precursors in a three-neck flask along with the required amount of octadecene (ODE), corresponding hydrohalic acid, and preformed butylammonium halide salt. The mixture was then heated to the desired reaction temperature to obtain a clear solution and then cooled naturally to room temperature. The free-standing monomer at high temperature underwent crystallization during cooling, and the solution became turbid, resulting in formation of the required microcrystals. Details of

the synthetic process, purification steps, and optimization processes are provided in the Supporting Information. Optical measurements of the samples could not be carried out in the solution phase because of their large particle size, and hence, measurements were carried out in the film by drop casting these microcrystal solutions on a glass slide. Details of the experiments are presented in the Experimental Section in the SI. Corresponding photoluminescence (PL) and photoluminescence excitation (PLE) spectra of L2PbX4 crystals are shown in Figure 1a−c. The chloride one showed no emission, but the PLE spectra showed a peak at around 334 nm (Figure 1a), which was also in agreement with the literature reports.29,30 Interestingly, L2PbBr4 crystals showed a highly intense emission at around 420 nm with a quantum yield (QY) of 18%, and the PLE spectra showed a band edge at 410 nm (Figure 1b). For iodide crystals, PL spectra showed a less intense peak at ∼560 nm (PLQY ≈ 2%), and from PLE, the band edge was estimated at around 520 nm (Figure 1c). All of the as-synthesized crystals were viewed via an optical microscope, and the images are presented in Figures S1−S3. For all cases, flakes like micron-size crystals were observed. Interestingly, in most cases, the edges of the crystals were observed to be sharp, possibly because of their single-crystal nature. Hence, single-crystal XRD measurements were further carried out for all three L2PbX4 crystals. From the measurements, the crystal phases were obtained and observed to be orthorhombic for all three cases having cell parameters a = b ≠ c and α = β = γ = 90°, but their space groups differed from each other (Tables S1−S3). The chloride system (L2PbCl4) has Cmc21 symmetry (Table S1) with cell parameters a = 344

DOI: 10.1021/acsenergylett.8b02349 ACS Energy Lett. 2019, 4, 343−351

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Figure 2. (a) PL spectra, (b) PLE spectra, and (c) powder XRD patterns of Mn-doped L2PbBr4 microcrystals prepared with different Pb to Mn initial intake ratios. The excitation wavelength for PL measurements was 350 nm, and the emission wavelength for PLE measurements was 600 nm. Pb to Mn ratios mentioned in the insets are the precursor ratios taken during the reaction. However, after purification, Mn present in these samples was 2.3, 3.1, and 4.2% with respect to Pb, respectively. The simulated XRD pattern was obtained from single-crystal XRD analysis. (d) Excited-state decay lifetime plot of Mn-doped L2PbBr4 microcrystals. The excitation wavelength was 350 nm, and the emission wavelength was 600 nm. The inset shows the fitted data of the plot. (e,f) Optical microscopic images in different resolutions of Mndoped L2PbBr4 microcrystals under UV irradiation (λ = 340−380 nm). Microcrystals were prepared with a 1:1 Pb to Mn precursor ratio.

27.780 Å, b = 7.9522 Å, c = 7.7609 Å, and α = β = γ = 90°. The inorganic layers were present along (n00) (n = 1, 2, 3, ...) planes, which were separated by organic spacer ligands (Figures 1d and S4). Especially in this case, pronounced distortion from the octahedral geometry of Pb(II) centers was observed, which was a very common phenomenon for [PbCl6]4− octahedra (Figure S5, Table S1).44,46,60 To further clarify, single octahedral units of three crystals are provided in Figure S5, which clearly shows that the Cl(ter)−Pb−Cl(ter) bond angle deviated from an ideal 180°, and inhomogeneous Pb−Cl, the bond length varied from 2.888 to 2.924 Å (Table S4). The other bromide and iodide systems contained a more regular octahedral geometry of Pb(II) centers; their inorganic layers were along (00n) (n = 1, 2, 3, ...) planes, and both systems acquired the same space group Pbca (Figure 1e,f and Tables S2 and S3) with cell parameters a = 8.235 Å, b = 8.120 Å, c = 27.528 Å, and α = β = γ = 90° for bromide crystals and a = 8.396 Å, b = 8.966 Å, c = 26.188 Å, and α = β = γ = 90° for iodide crystals. The volume of the crystals gradually increased from chloride to bromide to iodide, which was expected as the size of the respective halide ion increases (Tables S1−S3). Models showing the crystal packing of the unit cell from different views are presented in Figure 1d−f (Figures S4 and S6−S7). Single-crystal XRD analysis is a very local study to obtain unit cell information on the materials and was performed on a single crystal only. However, for the bulk crystallinity of the materials, powder XRD measurements were carried out for all samples, and the diffraction patterns are shown in Figure S8a− c. All XRD patterns showed excellent agreement with the

simulated XRD patterns obtained from single-crystal XRD analysis, and this signified that the samples were singlecrystalline in nature. All of the samples showed peaks at regular intervals, 6.45, 6.56, and 6.54° for chloride, bromide, and iodide systems, respectively, which suggested the distance between two inorganic layers separated by a butylammonium ion.29,30,46 Further, these crystals were doped successfully with Mn by taking corresponding Mn halide salts along with the other precursors (details of synthesis processes are in the Supporting Information). Compared with the undoped crystals, doping had hardly any impact on the morphology, unit cell, and powder XRD pattern. Optical microscopic images and a comparison table describing the unit cell parameters of the doped crystals are provided in Figures S9−S11 and Table S5, respectively. In all cases, the Pb to Mn ratio was maintained at 1:1, but less than 10% Mn (with respect to Pb) was observed from EDS measurements in all of these samples (Figures S12− S14). This confirmed that only a small amount of Mn got inside of the crystals. A comparison table (for all three halide systems) with the amounts of initial Mn intake in the reaction flask and incorporated in the crystal is presented in Table S6. Interestingly, though Mn was present in all of the crystals, the Mn d−d emission was observed only in the case of the bromide system (optical data and powder XRD patterns for the Mn-doped chloride and iodide crystals are provided in the Supporting Information, Figures S15 and S16). While the host showed emission at 420 nm, the secondary emission or dopant emission was observed at around 600 nm (Figure 2a). To investigate the origin of the Mn emission, PLE measurement of 345

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Figure 3. (a) EPR spectra of Mn-doped L2PbCl4, L2PbBr4, and L2PbI4 microcrystals. All of these doped microcrystals were prepared with a 2:1 Pb:Mn initial precursor ratio. (b) EPR spectra of Mn-doped L2PbBr4 obtained with different Pb:Mn precursor ratios, right column showing different Mn loading amount and Mn amount inside of the lattice with respect to Pb and (c) Mn PL lifetimes of Mn-doped L2PbBr4 microcrystals. The lifetime was measured at 600 nm, and the excitation wavelength was 350 nm. (d−f) PL spectra of Mn-doped L2PbBr4 microcrystals at cryogenic (−180 °C) and room (25 °C) temperatures prepared with 1:1, 1:2, and 1:4 Pb to Mn precursor ratios, respectively. The excitation wavelength was 350 nm.

flask and inside of the crystal with respective QYs is provided in Table S7. Further, to confirm the coordination environment of the dopant Mn(II) ion in these microcrystals, EPR spectroscopic study was carried out for all of the doped crystals, and corresponding X-band EPR spectra at room temperature are shown in Figure 3a. All spectra for the three crystals showed distinct hyperfine splitting with hyperfine splitting constants (A) of ∼97 G (for L2PbCl4, A = 98.16 G; for L2PbBr4, A = 97.92 G; and for L2PbI4, A = 98.92 G). Comparing the hyperfine splitting constant with the literature reports for Mndoped perovskites, it is confirmed that Mn was present in the +2 oxidation state and it was residing in place of Pb(II), experiencing an octahedral coordination environment around it.8,16 In the case of the bromide system, increasing the Mn intake amount from 25 to 400% with respect to Pb, a change in the EPR spectra was observed (Figure 3b). As the Mn concentration gradually increased, the six distinct peaks gradually merged together to give rise to a single broad peak. This observation follows well with other reports for Mn-doped CsPbCl3 nanocubes.16 Figure 3c shows the PL decay lifetimes for Mn d−d emissions at different Mn concentrations. A small but gradual decrease in the lifetime was observed, which also supported broadening of the EPR spectra due to Mn−Mn coupling at high Mn concentration.16

all of the samples was carried out at Mn emission peak maxima (λem = 600 nm), and these showed a band edge at around 410 nm (Figure 2b). This confirmed that the Mn emissions originated from exciton energy transfer from the host to the Mn d-states (Figure S17). Further, to understand the impact of Mn concentration on the optical property, PL spectra of different Mn-doped L2PbBr4 crystals, prepared with different Pb to Mn precursor ratios, are shown in Figure 2a. As observed, the intensity of the excitonic blue emission slowly diminished with evolution of intense Mn d−d emission at ∼600 nm, though the PLE spectra remained almost unchanged (Figure 2b). Powder XRD patterns of various samples prepared with different Pb to Mn ratios are presented in Figure 2c, suggesting that the crystal phase almost remained unaltered. Moreover, the most intense Mn emission with minimal host emission was obtained from the sample prepared with a precursor ratio of Pb to Mn 1:1, though in the lattice only 4.2% Mn was present with respect to Pb (Figure S13). The absolute QY recorded for this sample was 61%, and the phosphorescence lifetime of the Mn emission was measured to be 0.67 ms (Figure 2d). The millisecond order lifetime further confirmed that the emission at around 600 nm arises due to a spin-forbidden Mn d−d transition.15,48 Optical microscopic images of Mn-doped L2PbBr4 microcrystals in different resolutions are presented in Figure 2e,f. The comparison between the Pb to Mn ratio of initial intake in the reaction 346

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Figure 4. (a) PLQY of the Mn emission plotted against time. The crystals were drop-casted on a glass slide, and PL was measured for the same slide time to time, keeping it in open air. For the stability test, the doped microcrystals were prepared with a 1:1 Pb:Mn precursor ratio. (b) Corresponding PL spectra of respective samples. The excitation wavelength for PL measurements was 350 nm.

Figure 5. (a) Powder XRD patterns of undoped L2PbBr4 microcrystals after and before annealing at 200 °C for 1 h. (b,c) Optical microscopic images of the same sample under UV irradiation (λ = 340−380 nm) after and before annealing at 200 °C for 1 h, respectively, and (d) PL spectra of the corresponding microcrystals. The excitation wavelength for PL measurement was 350 nm. All measurements were carried out at room temperature.

systems, the energy transfer rate (picosecond order) remains always faster than the exciton recombination rate (nanosecond order), and at low temperature, the difference becomes larger as the excitonic recombination rate decreases, resulting in an increase in the Mn emission intensity.61 As the PL dependency of the 2D layered perovskite resided intermediate to these two cases, we assumed that this might be because of the layer structure where Mn ions had limited local environmental impact (only in 2D) and hence behaved like a hybrid structure of both perovskites and chalcogenides under low temperature. Moreover, the impact of low temperature on the Mn emission intensity changes drastically with Mn amount present in the crystals. Figure 3e,f clearly reflected that with an increase of the Mn content in the crystals, (from 4.2 to 6.4% with respect to Pb) the impact of low temperature on the PL intensity is minimized. This observation agrees well with previous reports on Mn-doped CsPbCl3 nanocrystals.61 The most exciting feature observed for these doped materials was their stability in retaining intense emission under drastic conditions. Figure 4a,b shows the stability plot and the corresponding PL spectra of Mn-doped L2PbBr4 microcrystals under ambient conditions. Our first batch of

While all of the above dopant-induced new properties in 2D perovskites were overlapping with those of Mn-doped chalcogenides/perovskites, recently it was established that the temperature-tuned Mn d−d emission of doped CsPbCl3 behaved opposite that for chalcogenides.61 To observe the lowtemperature effect on the PL property, the PL of Mn-doped L2PbBr4 samples was also measured at −180 °C. For comparison, Mn-doped CsPbCl3 nanocubes were also synthesized following the literature method,5 and PL was measured under identical conditions, where a marginal increase of the excitonic emission intensity along with a decrease in the dopant emission intensity was observed for these 2D layered perovskites (Figure 3d). However, the Mn emission intensity was completely quenched accompanied by a ∼5-fold increase in the host emission at low temperature for the 3D Mn-doped CsPbCl3 nanocubes (Figure S18).61 For 3D Mn-doped CsPbCl3 nanocubes, it is reported that the exciton energy transfer rate is slow (nanosecond order), and at low temperature, the exciton recombination rate becomes faster than the energy transfer rate in these perovskite nanoparticles. As a result, the Mn d−d emission intensity is decreased with lowered measuring temperature.61 However, for chalcogenide 347

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Figure 6. (a) Powder XRD patterns of Mn-doped L2PbBr4 microcrystals synthesized with a 2:1 precursor ratio of Pb to Mn after and before annealing at 200 °C for 1 h. (b,c) Optical microscopic images of the microcrystals under UV irradiation (λ = 340−380 nm) after and before annealing at 200 °C for 1 h, respectively, and (d) PL spectra of the corresponding microcrystals. The excitation wavelength for PL measurement was 350 nm. All measurements were carried out at room temperature.

thermally stable even beyond 200 °C. However, the roomtemperature PL of these as-prepared and annealed samples showed almost similar PL intensity (Figure 5d), suggesting that the emissive nature remained the same even after prolonged annealing in air. To observe the effect of solid-state annealing on doped microcrystals, two sets of microcrystal samples having different host to dopant emission intensities were selected. Figure 6a shows the XRD patterns of as-prepared and 1 h-annealed doped L2PbBr4 microcrystal films, where the peak intensities corresponding to (n00) (n = 1, 2, 3, ...) planes were also observed to be remarkably enhanced (∼100 fold). Corresponding optical microscopic images of the sample under UV irradiation after and before annealing were also analyzed and are presented in Figure 6b,c. Interestingly, while the preannealed sample showed both blue and orange emitting crystals, after annealing all of the crystals turned out to be orange, and Figure 6d presents the PL spectra of the doped L2PbBr4, which had considerable high-energy host emission intensity compared to dopant emission; upon annealing at 200 °C for 1 h, this showed drastic quenching of the excitonic emission. Importantly, the smaller crystals (Figure 6c) were blue-emitting, indicating that these were undoped, and after annealing, they merged with other doped orange-emitting crystals, resulting in formation of doped crystals with larger size (Figure 6b). This observation strongly supported our assumption of solid-state ripening, where smaller crystals were merged with the larger one. On the other hand, for the sample having predominant dopant emission over excitonic emission (Figure S23a), the dimensions of the crystals were also seen to increase during annealing (Figure S23b). Optical microscopic images for the preannealed sample of this reaction are shown in Figure 2e,f, which were comparatively of smaller dimension. Hence, for both cases, thermal treatment of doped and undoped samples follows a mechanism similar to that of solid-state ripening. However, in none of the cases did the dopant or host retain its emission at 200 °C, and after cooling, respective emissions reappeared and all properties were

samples, which were synthesized more than 7 months ago, still retained almost the entire original emission. The powder XRD patterns also remained identical (Figure S19). However, while these crystals were heated in air to study the thermal impact on their luminescence property, more interesting results were observed. Either by thermocycling the film from room temperature to 200 °C (keeping 1 h for one cycle) in an air oven for more than 10 cycles or by continuous heating at 200 °C for 24 h, their original emission was retained. The observation remained similar for both doped and undoped perovskites. However, features observed in the peak intensities in powder XRD patterns and the dimensions of the microstructures suggested that thermal annealing in the solid state indeed modulated these microstructures. Figure 5a shows the powder XRD patterns of as-prepared and 1 hannealed undoped L2PbBr4 microstructure films, where the peak intensities corresponding to (n00) (n = 1, 2, 3, ...) planes were observed to be remarkably enhanced (∼100 folds). Similarly, the optical microscopic images of the annealed sample (Figure 5b) showed an increase in the average size of the microcrystals compared to the as-prepared sample (Figure 5c). These results suggested that annealing indeed enhanced the crystallinity as well as dimensions of these microstructures. As the XRD peak intensities corresponding to (n00) (n = 1, 2, 3, ...) planes increased, microscopic images also showed that the planar dimension of the microcrystals increased. It might be assumed here that the inorganic layers were laterally present in the microcrystals, and these were viewed along the [100] direction. Hence, the mechanism followed here might be similar to solid-state ripening. On the basis of the above observation, a schematic model is presented in Figure S20. Importantly, after such a long time of annealing or even more than 10 rounds of thermocycling with exposure to air, the spacer organic ligands were not lost. Thermogravimetric analysis (TGA) study shows that the thermal decomposition temperature for this material is >250 °C (Figure S21), and above this temperature, PbBr2 was formed (Figure S22). Hence, it can be stated here that these layered perovskites are 348

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ACS Energy Letters Notes

measured at room temperature only. To compare the thermal stability of these microcrystals with the reported Mn-doped perovskites, a batch of Mn-doped CsPbCl3 nanocubes was synthesized following the traditional method5 and was subjected to thermal annealing. Interestingly, nanocubes lost their dopant as well as excitonic emission within 1 h of thermal annealing at 200 °C. During annealing, these nanocubes underwent a phase transformation from the emissive cubic phase to the nonemissive CsPb2Cl5 phase (Figure S24) and hence behaved differently than the layer perovskites.62 For doped chalcogenides, also the emission was seen to be quenched when heated (solid film) at 200 °C for 1 h in air (Figure S25).63 All of these observations suggest that both doped and undoped layered perovskite microcrystals are thermally stable compared to the chalcogenide and 3D perovskite nanocrystals, and they behave differently at cryogenic temperatures. In conclusion, a generic solution-phase synthesis to obtain undoped and doped single-crystalline microcrystals of layered perovskites (L2PbX4, X = Cl, Br and I) is reported. The reaction chemistry of using ammonium salts, the use of HX, the selection of appropriate spacer ligands, and the formation process of all single-crystalline microstructures are discussed. Mn ions are successfully doped in all three halide microcrystals, and only L2PbBr4 results in Mn d−d emission. Because of the layered structure where the exciton is more confined, a dopant emission with QY of ∼61 was observed for these microstructures. These microstructures showed unprecedented stability, and the emission intensity remained unchanged during thermocycling or annealing and was even stable for months in air. Solid-state annealing prompted the agglomeration of these nanostructures but did not quench the emission. While doping in 3D perovskites has been extensively studied, the report here for developing a generic strategy for successfully doping in 2D layered perovskite in solution would provide more platforms for further investigations for understanding the doping mechanism and the dopant-induced new materials properties in this new class of perovskite hosts.

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The authors declare no competing financial interest.

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ACKNOWLEDGMENTS S.K.D., A.D., and S.D.A. acknowledge CSIR for a fellowship. DST of India (SERB/F/7159/2016-2017) is acknowledged for funding.

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ASSOCIATED CONTENT

* Supporting Information S

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsenergylett.8b02349. Experimental section, optical images, and table containing parameters of single crystal XRD, EDS, and powder XRD patterns (PDF) Crystallographic file of L2PbCl4 (CIF) Crystallographic file of L2PbBr4 (CIF) Crystallographic file of L2PbI4 (CIF) Crystallographic file of Mn-doped L2PbCl4 (CIF) Crystallographic file of Mn-doped L2PbBr4 (CIF) Crystallographic file of Mn-doped L2PbI4 (CIF)

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. ORCID

Sumit Kumar Dutta: 0000-0002-9228-1916 Anirban Dutta: 0000-0001-9915-6985 Samrat Das Adhikari: 0000-0002-5670-5179 Narayan Pradhan: 0000-0003-4646-8488 349

DOI: 10.1021/acsenergylett.8b02349 ACS Energy Lett. 2019, 4, 343−351

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DOI: 10.1021/acsenergylett.8b02349 ACS Energy Lett. 2019, 4, 343−351