Less-Lead Control toward Highly Efficient Formamidinium-Based

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Less-lead control toward highly efficient formamidinium-based perovskite light-emitting diodes Xiaoli Zhang, Weigao Wang, Bing Xu, Haochen Liu, Huafeng Shi, Haitao Dai, Xinhai Zhang, Shuming Chen, Kai Wang, and Xiao Wei Sun ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.8b03590 • Publication Date (Web): 29 Jun 2018 Downloaded from http://pubs.acs.org on July 1, 2018

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ACS Applied Materials & Interfaces

Less-lead control toward highly efficient formamidinium-based perovskite light-emitting diodes Xiaoli Zhang†, Weigao Wang†, Bing Xu†, Haochen Liu†, Huafeng Shi†, Haitao Dai‡, Xinhai Zhang†, Shuming Chen*,†, Kai Wang*,†, Xiao Wei Sun*,† †

Department of Electrical & Electronic Engineering, Southern University of Science

and Technology, 518055, Shenzhen, China ‡

School of Science, Tianjin University, 300072, Tianjin, China

ABSTRACT GRAPHICS

KEY WORDS: Perovskite, nanocrystals, light-emitting diode, less-lead, formamidinium

ACS Paragon Plus Environment

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ABSTRACT: Formamidinium (FA)-based perovskite is an ideal option for the potential efficient LED in view of its high tolerance factor closer to 1. In this work, FA-cation based perovskite nanocrystals FA0.8Cs0.2PbxBr3 (x = 1.0, 0.8, 0.7, 0.6) are fabricated with stoichiometric modification. The adoption of less-lead precursor is confirmed to be a feasible and effective approach in inhibiting non-radiative recombination by diminishing the presence of uncoordinated metallic Pb atoms. Note that the subsequent devices require the optimized lead ratio for an optimum behavior, a clear influence of Pb ratio on perovskite LED has been established. No surprisingly, the less-lead perovskites exert positive roles on the perovskite LED performance, not only in terms of efficiency but also in stability. With an optimized composition FA0.8Cs0.2Pb0.7Br3, the perovskite LED displays the prominent performance with current efficiency of 28.61 cd A-1, about 11-fold improvement than the previous best record of pure FA-based perovskite. Additionally, the perovskite device degradation can be mitigated under operating conditions by properly altering precursor stoichiometry,

which can

be attributed to

the

hydrogen

reaction

under

moisture-induced ambient. The stoichiometric optimization of the metal Pb in the perovskite is an important strategy on the road to the further development of perovskite LEDs.


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INTRODUCTOIN The word “perovskite” has been ranked as one of the hottest topics in semiconductor materials science, and the counterpart optoelectronic devices as new runners have been brought to the forefront of research focus in recent years.1-10 The intensive investigation of metal halide perovskites with superior physicochemical properties such as long charge carrier diffusion lengths, tunable bandgaps and high charge carrier mobilities,11-13 have transcended photovoltaic applications. The newly emerged perovskite light-emitting diode (LED) has witnessed the vigorous development of these fascinating semiconductors. The first breakthrough in LEDs based on green CH3NH3PbBr3 (MAPbBr3) perovskite was achieved with a bright electroluminescence (EL) of 364 cd m-2 and external quantum efficiency (EQE) of 0.1%,14 and then 417 cd m-2 and current efficiency (CE) of 0.577 cd A-1.15 Only within a year, MAPbBr3-based perovskite LED was demonstrated 20-fold increase in luminous efficiency (4.0 lm W-1, 20000 cd m-2, EQE = 3.5%) over the first report with the aid of interfacial engineering technique.16 Up to now, the colloidal organometal halide perovskite MAPbBr3 nanoparticle-based LED exhibits a maximum CE (EQE) of 11.49 cd A-1 (3.8%),17 while the MAPbBr3 thin film LED records the stirring CE (EQE) of 42.9 cd A-1 (8.53%).18 The popularly studied metal halide perovskites present three-dimensional (3-D) structure and share the general ABX3 formula, which can only be stabilized by organic/inorganic A cations of CH3NH3+ (MA+), HC(NH2)2+ (FA+) and Cs+ in consideration of the rigid restriction on their ionic radii.19 According to the



Goldschmidt’s tolerance rule, the tolerance factor is directly related to the ionic radius of A, B and X, which is strictly constrained in the range of 0.9~1.0 for a stable cubic perovskite.20 Comparatively, FA+ cation has a larger ion radius (2.53 Å) than MA+ (2.17 Å) and Cs+ (1.80 Å) for the A-site substitute in perovskite, which is preferred for preparing outstanding perovskite with crystal stability in view of its higher tolerance factor closer to 1.21 Additionally, the reported excellent carrier lifetime and diffusion length make perovskite FAPbBr3 more competent in LED than MAPbBr3.22-23 Despite FA-based perovskite is an ideal option for the potential efficient LED, it is rarely reported. The first EL device based on pure FAPbBr3 shows a luminance of 1~2 cd m-2 and a CE of 0.005 cd A-1.24 The recent research reported by Yang Yang group explored a green FAPbBr3 perovskite LED with high brightness and efficiency (13000 cd m-2, CE = 2.65 cd A-1, EQE = 1.16%).25 Tae-Woo Lee group synthesized ligand-engineered colloidal FAPbBr3 nanoparticles and demonstrated the maximum current efficiency of 9.16 cd A-1 in LEDs based on it;26 they also reported high-efficiency polycrystalline perovskite LEDs based on FA-Cs mixed cations, and the thin film perovskite LEDs exhibited the maximum CE of 14.5 cd A-1.27 In our previous study, the performance of FAPbBr3 perovskite LEDs has been significantly improved through proper incorporation of inorganic Cs cation.28 With an optimized composition of FA0.8Cs0.2PbBr3, the LEDs exhibit encouraging current efficiency of ~10 cd A 1. Though some progresses have been achieved for FAPbBr3, there is still −

plenty of room to push that further, in comparison with the enormous achievements of MAPbBr3 perovskite LEDs. Hence, underscoring the urgent to reach an effective


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solution is imperative to overcome the EL efficiency limitations of FA-based perovskite LEDs. The recorded MAPbBr3 perovskite LEDs (CE = 42.9 cd A-1, EQE = 8.53%) was realized on the basis of effective management of exciton quenching through (1) fine and controllable stoichiometry modification and (2) optimized nanograin engineering.18 The exciton emission decay stemmed from the strong nonradiative energy transfer to trap states is a fundamental hamper in making efficient perovskite LEDs.29-30 The presence of halogen vacancies (VBr) and metallic Pb atoms acting as recombination centers degrades the luminescence by increasing the nonradiative decay rate.31-32 The usually employed equimolar solution-processed method revealed the emergence of Pb atoms in final perovskite products due to the unintended losses of halide atoms or incomplete reaction between the original precursors.33 The less-lead perovskite can relieve the notorious influence of metallic Pb. However, the reported less-lead perovskite processed through lead substitution mainly focus on low-toxic aspect irrespective of inferior device performance.34-38 The good news is that, as the recent researchers observed, the adoption of CsBr-rich or MABr-rich precursor is confirmed to be a feasible and effective approach in restraining metallic Pb and reducing the nonradiative defect densities in the perovskites, thus guiding to realize the performed perovskite LEDs.39, 18 Inspired by the surprising effects of stoichiometry modification on the perovskite LEDs, herein, with the aim to evaluate the possibility of using FA cation-rich precursor for the performed LEDs, we synthesize relatively less-lead FA-based



perovskite nanocrystals for the first time. Note that the subsequent devices require the optimized lead ratio for an optimum behavior, a clear influence of lead concentration on perovskite LED should be established as the same experimental procedures was followed for synthesis. Therefore, the variable lead proportion in precursors was used from 1.0 to 0.6 based on our previously reported the optimized perovskite FA0.8Cs0.2PbBr3.28 In detail, we fabricated perovskite nanocrytal FA0.8Cs0.2PbxBr3 (x = 1.0, 0.8, 0.7, 0.6), in which x is denoted as the metal cation Pb ratio in the formula. The optimized perovskite LED with less-lead x = 0.7 features extraordinary behavior, showing a 11-fold CE enhancement than the record-holding FAPbBr3 perovskite device, while maintains the same stability. No surprisingly, the less-lead perovskites exert key roles on the final LED performance, not only in terms of efficiency but also in stability. EXPERIMENTAL SECTION In a typical synthesis: 0.2 mmol FABr, 0.05 mmol CsBr and PbBr2 with varied ratio (~ 0.25, 0.2, 0.175, 0.15 mmol) were dissolved in 5 ml DMF with 0.15 ml Oleylamine and 1 ml Oleic Acid. The mixture was heated at 60 oC for 30 min. 1 ml of mixture was dropped into 10 ml toluene with vigorous stirring for 30 s. After centrifugation (4000 rpm for 3 min and 8500 rpm for 4 min) and purification the product was dissolved in THF (Tetrahydrofuran) for further use. The concentration of synthesized perovskite nanocrystals is 20 mg/ml, and there is no subsequent annealing treatment for the spin-coated perovskite nanocrystals.


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RESULTS AND DISCUSSION

Figure 1. (a) Transmission electron microscopic (TEM) image and (b) corresponding high-resolution TEM of perovskite nanocrystals (x = 0.7). As-formed colloidal FA0.8Cs0.2PbxBr3 (x = 1.0, 0.8, 0.7, 0.6) nanocrystals are 13 ± 3.3 nm in size with nearly cubic shape (Figure 1a, x = 0.7 as a representative). The finely tuned stoichiometric proportion does not lead to obvious morphological evolution, as TEM images of all samples shown in supporting information (Figure S1). The single crystalline FA0.8Cs0.2Pb0.7Br3 as displayed by high-resolution TEM (Figure 1b) exhibits the characteristic lattice spacing of 0.326 nm, which is corresponding to the (211) plane of the cubic perovskite structure. The crystalline nature of all fabricated FA0.8Cs0.2PbxBr3 nanocrystals is confirmed by the selected area electron diffraction (SAED) measurements (Figure S1).



Figure 2. (a) Absorption spectra and (b) PLspectra of perovskite with varied Pb ratio in precursors. The inset is the photo of as-formed perovskite nanocrystals under ultraviolet excitation. (c) XRD patterns of different samples. (d) XPS spectra of metallic Pb atoms as a function of Pb ratio in different samples. The effect of stoichiometric changes on the optical properties was detected by means of absorption and photoluminescence spectroscopy (Figure 2a and b). A blue shift of green emission peak from 526 to 522 nm is observed, which is attributed to the widened band gap (as calculated from absorption spectra, see Table S1). The formation of hydrogen bonding of FA with water molecules contributes to the extended band gap for the moisture exposed samples, as indicated by the early proposal.40 The crystal structure of as-prepared perovskite deposited on the glass substrate was analyzed by measuring x-ray diffraction (XRD) patterns (Figure 2c). The diffraction peaks located at 15.0o, 21.2o, 30.3o, 33.9o, 37.2o, 43.4o and 46.0o are


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assigned to (100), (110), (200), (210), (211), (220) and (300) planes, respectively. The stoichiometric modification has little effects on the crystal perovskite structure and peak positions. A closer observation reveals that the excess use of FA/Cs cation in less-lead precursors (x = 0.6) creates secondary phase in the final products, as evidenced by the exotic diffraction peaks marked with red star in XRD patterns. The introduced impurity phases such as FA4PbBr6/Cs4PbBr6 would make an impact on the radiative recombination and the followed device performance (x = 0.6). To unveil the chemical changes in the as-prepared FA0.8Cs0.2PbxBr3 (x = 1.0, 0.8, 0.7, 0.6) nanocrystals fabricated with different stoichiometries, we conducted x-ray photoelectron spectroscopy (XPS). The weak signal peaked at around 137 eV is assigned to metallic Pb (Figure 2d).41 The perovskite obtained with equimolar precursor (x = 1.0) reveals evident peak, suggesting the metallic Pb formed in the final products. Whereas, the peak intensity is dramatically declined for the less-lead perovskite samples (x = 0.8, 0.7, 0.6), indicating the presence of hazardous Pb atoms is successfully suppressed by stoichiometry control. The correspondingly increased Cs/Pb ratio confirms again the varied Pb content in the products (Table S1, see supporting information). The dependence of bandgap, PL and XPS of different samples on the Pb ratio x is summarized in Table S1.



Figure 3. (a) Schematic illustration of the structure of perovskite LEDs, and EL spectra and luminous photograph of device driven at 4 V. (b) High-binding energy secondary-electron cutoff regions and VB-edge region of perovskite nanocrystals. (c) Energy band alignment of the perovskite LEDs. To illustrate the actions of stoichiometric tuning on the perovskite LEDs, the as-formed perovskite nanocrystals were employed as the emitting materials for LEDs. The relatively high quantum yield of as-prepared perovskite nanocrystals (70-85%) is conducive to the potential outstanding performance. For comparison, all the devices were fabricated with the same structural configuration, as displayed in Figure 3a. The flat-band energy levels of the different components in the device structure are shown in the schematic energy band diagram, in which electrons and holes are transported from TPBi and TFB, respectively, followed by injection and radiative recombination in the active perovskite emitting layer. The balance of carriers injection is crucially important to the device performance, the perfectly matched energy levels of different


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components in the device can enable the behaved perovskite LEDs. Therefore, the VB and CB energy levels of as-fabricated perovskite nanocrystals were measured using ultraviolet photoelectron spectroscopy (UPS). On the strength of the extracted values of high-binding energy secondary-electron cut-off (Ecutoff) and the onset energy (Eonset), the VB levels of FA0.8Cs0.2PbxBr3 are computed to be -6.07, -5.80, -5.73 and -5.81 eV for Pb ratio x = 1.0, 0.8, 0.7, 0.6, respectively (Figure 3c). For less-lead perovskite LEDs, the hole injection is improved as expected; we can see the gradually lowered VB and then the reduced hole injection barrier at the interface between perovskite and hole transport layer. A little increase of VB for perovskite x = 0.6 is discovered, and the instability of excessively less lead perovskite against moisture could account for this abnormality, which will be offered sufficient elaboration in the followed sections.

Figure 4. (a) Current density-voltage, (b) luminance-voltage, (c) CE-current density and (d) EQE-current density characteristics of perovskite LEDs based on FA0.8Cs0.2PbxBr3 (x = 1.0, 0.8, 0.7, 0.6).



The characterization of perovskite LEDs based on FA0.8Cs0.2PbxBr3 (x = 1.0, 0.8, 0.7, 0.6) nanocrystals are displayed in Figure 4. As x is decreased from 1.0 to 0.7, the maximum luminance and efficiency are greatly enhanced. For example, the reference perovskite LED (x = 1.0) exhibits a luminance and a CE (EQE) of 23720 cd m-2 and 9.38 cd A-1 (2.67%), which are demonstrated to be 1.7- and 2.1- (-1.91)fold increased for those of the devices with x = 0.8, respectively. Furthermore, the device with less-lead perovskite x = 0.7 records the best behavior, with maximum luminance, CE and EQE of 45440 cd m-2, 28.61 cd A-1 and 6.75%. The perovskite device with very little Pb ratio (x = 0.6) shows decreased performance (CE = 18.78 cd A-1, EQE = 4.96%), but still far ahead of the inferior action of perovskite with equimolar precursor. Comparatively, the extra controlled device with excess Pb ratio (x = 1.25) was made to confirm disgusting activity (CE = 6.96 cd A-1, EQE = 1.96%) induced by Pb atoms, as indicated in Figure S2. It can be concluded that optimized Pb ratio is vital to the desirable device performance, and too much or too little heavy metal Pb generated in perovskite structure is disastrous to device performance. The detailed device characterization is summarized in Table 1 and Table S2. The comparable device performance with varied Pb ratio provokes the implications in the rational optimization of perovskite LEDs with proper stoichiometric adjustment.


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Table 1. The summary of device performance based on different perovskite NCs.

Pb content

Max. EQE

Max. CE

Max. L

(%)

(cd A-1)

(cd m-2)

Von (V)

x = 1.0

3.4

2.67

9.38

23720

x = 0.8

3.4

5.09

19.67

39830

x = 0.7

3.3

6.75

28.61

45440

x = 0.6

3.3

4.96

18.78

14960

Figure 5. (a) EL spectra of device with x = 1.0 and (b) x = 0.7 as a function of time. (c) EL spectra of device x = 0.7 with different driven voltage. (d) Devices stability over



time, the luminance is collected at 4 V and normalized to the initial brightness of different devices. As we known, stability is a commonly confronted problem for perovskite study. The low energetic barrier for perovskite formation facilitates low-cost solution processing, whereas the chemical and structural metastability in ambient environment in turn degrades perovskite performance and hinders commercial application. Thus, solving this problem could bridge the gap between commercialization, low-cost fabrication and exceptional performance of perovskite. In our work, the perovskite LED with equimolar precursor (x = 1.0) experiences more than 50% luminance degradation during only two minutes lighting, while the less-lead perovskite devices exhibit surprisingly improved stability, especially for LED with perovskite of x = 0.7 (Figure 5). It suggests that the stability of the perovskite device can be properly improved by finely altering precursor stoichiometry. As reported in the literature, water molecules can spontaneously penetrate the perovskite lattice and form hydrogen bonds with organic cation at high-humidity levels, followed by catalyzing the decomposition of perovskite.42-44 The transformation of perovskite from physically uptake of water molecules to chemical transition to monohydrate and then hydration to dehydration convinces the perovskite degradation pathway. Intriguingly, it has been conversely reported that the moderate water molecules or moisture exposure can assist the uniform perovskite thin film and better device performance.45-47 These contradictory claims can be harmonized by the reversibility of hydration, that is, water may be beneficial by complexing with


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solid-state perovskite.48 In our study, though the perovskite was prepared in inert atmosphere, all the device measurements were executed under moisture-induced ambient. Moisture-exposed perovskite nanocrystals undergo a hydration reaction, but this process is significantly retarded compared to that in thin films, contributing to the stability of perovskite nanocrystals in high relative humidity of 50%-70%.41 On the other hand, moderately adsorbed moisture aids the hydrogen bonding interactions between the organic cation and halide ions of the perovskite lattice, especially for less-lead perovskite with rich organic cation (x = 0.7, 0.6) (Figure 5d), providing perovskite structural stability in a limited degree.49 Performance degradation is a major concern confronted for perovskite LEDs, more attention and insight investigations are needed for the fabrication of efficient and stable devices. There are various reasons for the unsatisfied perovskite devices stability, and the response strategies have been reported in recent researches. Stability against water and oxygen degradation can be improved via fabricating all-metal-oxide devices.50 Using stable perovskite emitting materials such as all-inorganic perovskite CsPbBr3 can make devices exhibit stable activity over repeated bias voltage scans in ambient conditions.51-53 by effectively

The improvement of the perovskite stability can be realized

restraining the thermally activated ion migration existed in perovskite

devices.54-56 Further advances of perovskite stability also rely on the compositional variation and phase transformation of perovskites, effective ligands, and architectural innovations.57-60 Though lots of strategies have been adopted to improve perovskite stability, the practical provskite devices are far from the commercializing. Hence,



improving perovskite device stability is a huge challenge, and still have a long way for exploration. Summing up the device studies, it is important to remark that the less-lead control is of great utility to high quality and reproducibility of perovskite LED. The superior performance (x = 0.7) can be ascribed to the following reasons: (1) the as-formed perovskite nanocrystals with less-lead diminish the presence of metal Pb in the products, inhibiting non-radiative recombination caused by uncoordinated metallic Pb atoms, as indicated by the increased PL lifetime (Figure S4); (2) the perfectly matched energy levels of perovskite with proper lead ratio facilitates hole injection with lowered energy barrier; (3) moderately moisture-exposed perovskite assists stable device performance with the hydrogen bonding interactions between the organic cation and halide ions, and the properly rich organic cation of less-lead perovskite manifests structural stability and prominent performance. CONCLUSIONS We have successfully formed less-lead perovskite FA0.8Cs0.2PbxBr3 (x = 1.0, 0.8, 0.7, 0.6) nanocrystals, which are served as emitting layer in LEDs and displayed outstanding behavior. For the optimized less-lead perovskite LED (x = 0.7), the recorded performance have been reported, such as the highest CE (28.61 cd A-1), about 11-fold improvement than the previous best record (2.65 cd A-1). The excellent performance is mainly attributed to the restraining the presence of metallic Pb atoms and the lowered hole injection barrier for less-lead perovskite. Additionally, the less-lead perovskite with rich organic cation exhibit enhanced stability, the moderate


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water molecule in perovskite not only relieves the device degradation but also properly enhance device stability through strong hydrogen bonding. In summary, less-lead control toward efficient perovskite LEDs has been confirmed in this work, which provides a feasible and practical approach for the fabrication of performed device. ASSOCIATED CONTENT Supporting Information The Supporting Information is available free of charge on the ACS Publications websites. Experimental part; TEM images, the summary of characterization of all samples, the device characterization for extra lead perovskites, the devices performance driven at 4 V, the PL lifetime of all samples (PDF). AUTHOR INFORMATION Corresponding Authors *

E-mail: [email protected], [email protected], [email protected]

Author Contributions The authors Dr. Xiaoli Zhang, Mr. Weigao Wang and Dr. Bing Xu contributed equally to this work. Notes The authors declare no competing financial interest. ACKNOWLEDGEMENTS



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The work is supported by The National Key Research and Development Program of China administrated by the Ministry of Science and Technology of China (No. 2016YFB0401702), National Natural Science Foundation of China (No. 61674074 61704072

and

51402148),

China

Postdoctoral

Science

Foundation

(No.

2017M610484 and 2017M612497), Shenzhen Peacock Team Project (No. KQTD2016030111203005). REFERENCES (1) Baena, J. P. C.; Steier, L.; Tress, W.; Saliba, M.; Neutzner, S.; Matsui, T.; Giordano, F.; Jacobsson, T. J.; Kandada, A. R. S.; Zakeeruddin, S. M.; Petrozza, A.; Abate, A.; Nazeeruddin, M. K.; Grätzel, M.; Hagfeldt, A. Highly Efficient Planar Perovskite Solar Cells Through Band Alignment Engineering. Energy Environ. Sci. 2015, 8, 2928-2934. (2) Zhang, X.; Wang, W.; Xu, B.; Liu, S.; Dai, H.; Bian, D.; Chen, S.; Wang, K.; Sun, X. W. Thin Film Perovskite Light-emitting Diode Based on CsPbBr3 Powders and Interfacial Engineering. Nano Energy 2017, 37, 40-45. (3) Saliba, M.; Wood, S. M.; Patel, J. B.; Nayak, P. K.; Huang, J.; Alexander-Webber, J. A.; Wenger, B.; Stranks, S. D.; Horantner, M. T.; Wang, J. T.; Nicholas, R. J.; Herz, L. M.; Johnston, M. B.; Morris, S. M.; Snaith, H. J.; Riede, M. K. Structured Orangic-inorganic Perovskite Toward a Distributed Feedback Laser. Adv. Mater. 2016, 28, 923-929. (4) Qasim, K.; Wang, B.; Zhang, Y.; Li, P.; Wang, Y.; Li, S.; Lee, S.; Liao, L.; Lei, W.; Bao, Q. Solution-processed Extramely Efficient Multicolor Perovskite


Page 19 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Light-emitting Diodes Utilizing Doped Electron Transport Layer. Adv. Funct. Mater. 2017, 21, 1606874. (5) Zhang, X.; Xu, B.; Zhang, J.; Gao, Y.; Zheng, Y.; Wang, K.; Sun, X. W. All-Inorganic Perovskite Nanocrystals for High-Efficiency Light Emitting Diodes: Dual-Phase CsPbBr3-CsPb2Br5 composites. Adv. Funct. Mater. 2016, 26, 4595-4600. (6) Shin, S. S.; Yeom, E. J.; Yang, W. S.; Hur, S.; Kim, M. G.; Im, J.; Seo, J.; Noh, J. H.; IIseok, S. Colloidally Prepared La-doped BaSnO3 Electrodes for Effiecient, Photostable Perovskite Solar Cells. Science 2017, 356, 167-171. (7) Dong, R.; Fang, Y.; Chae, J.; Dai, J.; Xiao, Z.; Dong, Q.; Yuan, Y.; Centrone, A.; Zeng, X. C.; Huang, J. High-Gain and Low-Driving-Voltage Photodetectors Based on Organolead Triiodide Perovskites. Adv. Mater. 2015, 27, 1912-1918. (8) Zhang, X.; Xu, B.; Wang, W.; Liu, S.; Liu, Y.; Chen, S.; Wang, K.; Sun, X. W. Plasmonic Perovskite Light-Emitting Diodes Based on the Ag-CsPbBr3 System. ACS Appl. Mater. Interfaces 2017, 9, 4926-4931. (9) Long, M.; Zhang, T.; Xu, W.; Zeng, X.; Xie, F.; Li, Q.; Chen, Z.; Zhou, F.; Wong, K.

S.;

Yan,

K.;

Xu,

J.

Large-Grain

Formamidinium

PbI3-xBrx

for

High-Performance Perovskite Solar Cells via Intermediate Halide Exchange. Adv. Energy Mater. 2017, 7, 1601882. (10) Cho, H.; Wolf, C.; Kim, J. S.; Yun, H. J.; Bae, J. S.; Kim, H.; Heo, J. M.; Ahn, S.; Lee, T. A. High-Efficiency Solution-Processed Inorganic Metal Halide Perovskite Light-Emitting Diodes. Adv. Mater. 2017, 29, 1700579.



(11) Lin, Q. Q.; Armin, A.; Nagiri, R. C. R.; Burn, P. L.; Meredith, P. Electro-optics of Perovskite Solar Cells. Nat. Photonics 2015, 9, 106-112. (12) Pellet, N.; Gao, P.; Gregori, G.; Yang, T. Y.; Nazeeruddin, M. K.; Maier, J.; Grätzel, M. Mixed-Organ-Cation Perovskite Photovoltaics for Enhanced Solar-Light Harvesting. Angew. Chem. 2014, 53, 3151-3157. (13) Zhang, J.; Xu, B.; Johansson, M. B.; Hadadian, M.; Baena, J. P. C.; Liu, P.; Hua, Y.; Vlachopoulos, N.; Johansson, E. M. J.; Boschloo, G.; Sun, L.; Hagfeldt, A. Constructive Effects of Alkyl Chains: A Strategy to Design Simple and Non-Spiro Hole Transporting Materials for High-Efficiency Mixed-Ion Perovskite Solar Cells. Adv. Energy Mater. 2016, 6, 1502536. (14) Tan , Z.-K.; Moghaddam, R. S.; Lai, M. L.; Docampo, P.; Higler, R.; Deschler, F.; Price, M.; Sadhanala, A.; Pazos, L. M.; Credgington, D.; Hanusch, F.; Bein, T.; Snaith, H. J.; Friend, R. H. Bright Light-Emitting Diodes Based on Organometal Halide Perovskite. Nat. Nanotechnol. 2014, 9, 687-692. (15) Kim, Y. H.; Cho, H.; Heo, J. H.; Kim, T. S.; Myoung, N.; Lee, C. L.; Im, S. H.; Lee, T. W. Multicolored Organic/Inorganic Hybrid Perovskite Light-Emitting Diodes. Adv. Mater. 2015, 7, 1248-1254. (16) Wang, J.; Wang, N.; Jin, Y.; Si, J.; Tan, Z.; Du, H.; Cheng, L.; Dai, X.; Bai, S.; He, H.; Ye, Z.; Lai, M. L.; Friend, R. H.; Huang, W. Interfacial Control Toward Efficient and Low-Voltage Perovskite Light-Emitting Diodes. Adv. Mater. 2015, 14, 2311-2316.


Page 20 of 28

Page 21 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(17) Xing, J.; Yan, F.; Zhao, Y.; Chen, S.; Yu, H.; Zhang, Q.; Zeng, R.; Demir, H. V.; Sun, X.; Huan, A.; Xiong, Q. High-Efficiency Lght-Emitting Diodes of Organometal halide Perovskite Amorphous Nanoparticles. ACS Nano 2016, 10, 6623-6630. (18) Cho, H.; Jeong, S.-H.; Park, M.-H.; Kim, Y.-H.; Wolf, C.; Lee, C.-L.; Heo, J. H.; Sadhanala, A.; Myoung, N.; Yoo, S.; Im, S. H.; Friend, R. H.; Lee, T.-W. Overcoming the Electroluminescence Efficiency Limitations of Perovskite Light-Emitting Diodes. Science 2015, 350, 1222-1225. (19) Stoumpos, C. C.; Kanatzidis, M. G. The Renaissance of Halide Perovskites and Their Evolution as Emerging Semicondutors. Accounts of Chemical Research 2015, 48, 2791-2802. (20) Goldschmidt, V. M. Die Gesetze Der Krystallochemie. Naturwissenschaften 1926, 14, 477-485. (21) Jacobsson, T. J.; Correa-Baena, J.-P.; Pazoki, M.; Saliba, M.; Schenk, K.; Grätzel, M.; Hagfeldt, A. Exploration of the Compositional Space for Mixed Lead Halogen Perovskites for High Efficiency Solar Cells. Energy Environ. Sci. 2016, 9, 1706-1724. (22) Zhumekenov, A. A.; Saidaminov, M. I.; Haque, M. A.; Alarousu, E.; Sarmah, S. P.; Murali, B.; Dursun, I.; Miao, X.-H.; Abdelhady, A. L.; Wu, T.; Mohammed, O. F.; Bakr, O. M. Formamidinium Lead Halide Perovskite Crystals with Unprecedented Long Carrier Dynamics and Diffusion Length. ACS Energy Lett. 2016, 1, 32-37.



(23) Hanusch, F. C.; Wiesenmayer, E.; Mankel, E.; Binek, A.; Angloher, P.; Fraunhofer, C.; Giesbrecht, N.; Feckl, J. M.; Jaegermann, W.; Johrendt, D.; Bein, T.; Docampo, P. Efficient Planar Heterojunction Perovskite Solar Cells Based on Formamidinium Lead Bromide. J. Phys. Chem. Lett. 2014, 5, 2791-2795. (24) Aygüler, M. F.; Weber, M. D.; Puscher, B. M. D.; Medina, D. D.; Docampo, P.; Costa, R. D. Light-Emitting Electrochemical Cells Based on Hybrid Lead Halide Perovskite Nanoparticles. J. Phys. Chem. C. 2015, 119, 12047-12054. (25) Meng, L.; Yao, E. P.; Hong, Z.; Chen, H.; Sun, P.; Yang, Z.; Li, G.; Yang, Y. Pure Formamidinium-Based Perovskite Light-Emitting Diodes with High Efficiency and Low Driving Voltage. Adv. Mater. 2016, 4, 1603826. (26) Kim, Y. H.; Lee, G. H.; Kim, Y. T.; Wolf, C.; Yun, H. J.; Kwon, W.; Park, C. G.; Lee, T. W. High Efficiency Perovskite Light-Emitting Diodes of Ligand-Engineered Colloidal Formamidinium Lead Bromide Nanoparticles. Nano Energy 2017, 38, 51-58. (27) Cho, H.; Kim, J. S.; Wolf, C.; Kim, Y. H.; Yun, H. J.; Jeong, S. H.; Sadhanala, A.; Venugopalan, V.; Choi, J. W.; Lee, C. L.; Friend, R. H.; Lee, T. W. High-Efficiency Polycrystalline Perovskite Light-Emitting Diodes based on Mixed cations. ACS Nano 2018, 12, 2883-2892. (28) Zhang, X.; Liu, H.; Wang, W.; Zhang, J.; Xu, B.; Karen, K. L.; Zheng, Y.; Liu, S.; Chen, S.; Wang, K.; Sun, X. W. Hybrid Perovskite Light-Emitting Diodes Based on Perovskite Nanocrystals with Organic-Inorganic Mixed Cations. Adv. Mater. 2017, 29, 1606405.


Page 22 of 28

Page 23 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(29) Nitsch, K.; Hamplová, V.; Nikl, M.; Polák, K.; Rodová, M. Lead Bromide and Ternary Alkali Lead Bromide Single Crystals-Growth and Emission Properties. Chem. Phys. Lett. 1996, 258, 518-522. (30) Nikl, M.; Nitsch, K.; Fabeni, P.; Pazzi, G. P.; Gurioli, M.; Santucci, S.; Phani, R.; Scacco, A.; Somma, F. Luminescence of CsPbBr3-like Quantum Dots in CsBr Single Crystals. Phys. E 1999, 4, 323-331. (31) Du, M.-H. Density Functional Calculations of Native Defects in CH3NH3PBI3: Effects of Spin-Orbit Coupling and Self-Interaction Error. J. Phys.Chem. Lett. 2015, 6, 1461-1466. (32) Dulkeith, E.; Ringler, M.; Klar, T. A.; Feldmann, J. Gold Nanoparticles quench fluorescence by phase induced radiative rate suppression. Nano Lett. 2005, 5, 585-589. (33) Lindblad, R.; Jena, N. K.; Philippe, B.; Oscarsson, J.; Bi, D.; Lindblad, A.; Mandal, S.; Pal, B.; Sarma, D. D.; Karis, O.; Siegbahn, H.; Johansson, E. M. J.; Odelius, M.; Rensmo, H. Electronic Structure of CH3NH3PbX3 Perovskites: Dependence on the Halide Moiety. J. Phys. Chem. C 2015, 119, 1818-1825. (34) Yang, Z.; Rajagopal, A.; Chueh, C.-C.; Jo, S. B.; Liu, B.; Zhao, T.; Jen, A. K. Y. Stable Low-Bandgap Pb-Sn Binary Perovskits for Tandem Solar Cells. Adv. Mater. 2016, 40, 8990-8997. (35) Liao, W.; Zhao, D.; Yu, Y.; Shrestha, N.; Ghimire, K.; Grice, C. R.; Wang, C.; Xiao, Y.; Cimaroli, A. J.; Ellingson, R. J.; Podraza, N. J.; Zhu, K.; Xiong, R.-G.; Yan, Y. Fabrication of Efficient Low-Bandgap Perovskite Solar Cells by



combining Formamidinium Tin Iodide with Methylammonium Lead Iodide. J. Am. Chem. Soc. 2016, 138, 12360-12363. (36) Lyu, M.; Zhang, M.; Cooling, N. A.; Jiao, Y.; Wang, Q.; Yun, J.-H.; Vaughan, B.; Triani, G.; Evans, P.; Zhou, X.; Feron, K.; Du, A.; Dastoor, P.; Wang, L. Highly Compact and Uniform CH3NH3Sn0.5Pb0.5I3 Films for Efficient Panchromatic Planar Perovskite Solar Cells. Sci. Bull. 2016, 61, 1558-1562. (37) Zhang, X.; Cao, W. Wang, W.; Xu, B.; Liu, S.; Dai, H.; Chen, S.; Wang, K.; Sun, X. W. Efficient Light-Emitting Diodes Based on Green Perovskite Nanocrystals with Mixed-Metal Cations. Nano Energy 2016, 30, 511-516. (38) Shai, X.; Zuo, L.; Sun, P.; Liao, P.; Huang, W.; Yao, E.; Li, H.; Liu, S.; Shen, Y.; Wang, M. Efficient Planar Perovskite Solar Cells Using Halide Sr-substituted Pb Perovskite. Nano Energy 2017, 36, 213-222. (39) Yantara, N.; Bhaumik, S.; Yan, F.; Sabba, D.; Dewi, H. A.; Mathews, N.; Boix, P. P.; Demir, H. V.; Mhaisalkar, S. Inorganic Halide Perovskite for Efficient Light-Emitting Diodes. J. Phys. Chem. Lett. 2015, 6, 4360-4364. (40) Grancini, G.; D'Innocenzo, V.; Dohner, E. R.; Martino, N.; Kandada, A. R. S.; Mosconi, E.; De Angelis, F.; Karunadasa, H. I.; Hoke, E. T.; Petrozza, A. CH3NH3PbI3 Perovskite Single Crystals: Surface Photophysics and Their Interaction with the Environmant. Chem. Sci. 2015, 6, 7305-7310. (41) Gonzalez-Carrero, S.; Galian, R. E.; Pérez-Prieto, Maximizing the Emissive Properties of CH3NH3PbBr3 Perovskite Nanoparticles. J. J. Mater. Chem. A 2015, 3, 9187-9193.


Page 24 of 28

Page 25 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(42) Christians, J. A.; Herrera, P. A. M.; Kamat, P. V. Transformation of the Excited State and Photovoltaic Efficiency of CH3NH3PbI3 Perovskite Upon Controlled Exposure to Humidified Air. J. Am. Chem. Soc. 2015, 137, 1530-1538. (43) Yang, J. L.; Siempelkamp, B. D.; Liu, D. Y.; Kelly, T. L. Investigation of CH3NH3PbI3 Degradation Rates and Mechanisms in Controlled Humidity Environments Using in Situ Techniques. ACS Nano 2015, 9, 1955-1963. (44) Leguy, A.; Hu, Y.; Campoy-Quiles, M.; Alonso, M. I.; Weber, O. J.; Azarhoosh, P.; Schilfgaarde, M. V.; Weller, M. T.; Bein, T.; Nelson, J.; Docampo, P.; Barnes, P. R. F. Reversible Hydration of in CH3NH3PbI3 Films, Single Crystals, and Solar Cells. Chem. Mater. 2015, 27, 3397-3407. (45) Zhang, W.; Saliba, M.; Moore, D. T. Pathak, K.; Hörantner, M. T.; Stergiopoulos, T.; Stranks, S. D.; Eperon, G. E.; Alexander-Webber, J. A.; Abate, A.; Sadhanala, A.; Yao, S.; Chen,Y.; Friend, R. H.; Estroff, L. A.; Wiesner, U.; Snaith, H. J. Ultrasmooth

Organic-Inorganic

Perovskite

Thin-Film

Formation

and

Crystallization for Efficient Planar Heterojunction Solar Cells. Nat. Commun. 2015, 6, 6142. (46) Zhou, H.; Chen, Q.; Li, G.; Luo, S.; Song, T. B.; Duan, H.-S.; Hong, Z.; You, J.; Liu, Y.; Yang, Y. Interface Engineering of Highly Efficient Perovskite Solar Cells. Science 2014, 345, 542-46. (47) Eperon, G. E.; Habisreutinger, S. N.; Leijtens, T.; Bruijnaers, B. J.; van Franeker, J. J.; deQuilettes, D. W.; Pathak, S.; Sutton, R. J.; Grancini, G.; Ginger, D. S.;



Janssen, R. A.; Petrozza, A.; Snaith, H. J. The Importance of Moisture in Hybrid Lead Halide Perovskite Thin Film Fabrication. ACS Nano 2015, 9, 9380-9393. (48) Manser, J. S.; Saidaminov, M. I.; Christians, J. A.; Bakr, O. M.; Kamat, P. V. Making and Breaking of Lead Halide Perovskites. Acc. Chem. Res. 2016, 49, 330-338. (49) Quarti, C.; Grancini, G.; Mosconi, E.; Bruno, P.; Ball, J. M.; Lee, M. M.; Snaith, H. J.; Petrozza, A.; De. Angelis, F. The Raman Spectrum of the CH3NH3PbI3 Hybrid Perovskite: Interplay of Theory and Experiment. J. Phys. Chem. Lett. 2014, 5, 279-284. (50) You, J.; Meng L.; Song T.; Guo, T.; Yang, Y. (Michael); Chang W.; Hong, Z.; Chen, H.; Zhou H.; Chen, Q.; Liu, Y.; Marcol, N.; Yang Y. Improved Air Stability of Perovskite Solar Cells via Solution-processed Metal Oxide Transport Layers. Nature Nanotechnology 2015, 230, 1-9. (51) Wei, Z.; Perumal, A.; Su, R.; Sushant, S.; Xing, J.; Zhang, Q.; Tan, S. T.; Demir, H. V.; Xiong, Q. Solution-processed Highly Bright and Durable Cesim Lead Halide Perovskite Light-emitting Diodes. Nanoscale 2016, 8, 18021-18026. (52) Kulbak, M.; Cahen, D.; Hodes, G. How Important is the Organic Part of Lead Halide Perovskite Photovoltaic Cells? Efficient CsPbBr3 Cells. J. Phys. Chem. Lett. 2015, 6, 2452–2456. (53) 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. Enhanced Optical and Electrical Properties of Polymer-Assisted All-Inorganic Perovskites for Light-Emitting Diodes. Adv. Mater. 2016, 28, 8983–8989.


Page 26 of 28

Page 27 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(54) Zhang, L.; Yang, X.; Jiang, Q.; Wang, P.; Yin, Z.; Zhang, X.; Tan, H.;Yang, Y.(Michael), Wei, M.; Sutherland, B. R.; Sargent, E. H.; You, J. Ultra-Bright and Highly Efficient Inorganic Based Perovskite Light-Emitting Diodes. Nat. Commun. 2017, 8, 15640. (55) Pazoki, M.; Wolf, M. J.; Edvinsson, T.; Kullgren, J. Vacancy Dipole Interactions and the Correlation with Monovalent Cation Dependent Ion Movement in Lead Halide Perovskite Solar Cell Materials. Nano Energy 2017, 38, 537–543. (56) Li, D.; Wu, H.; Cheng, H.-C.; Wang, G.; Huang, Y.; Duan, X. Electronic and Ionic Transport Dynamics in Organolead Halide Perovskites. ACS Nano 2016, 10, 6933−6941. (57) Zhang, X.; Xu, B.; Zhang, J.;, Gao, Y.; Zheng, Y.; Wang, K.; Sun, X. W. All-Inorganic Perovksite Nanocrystals for High-Efficiency Light-Emitting Diodes: Dual-Phase CsPbBr3-CsPb2Br5 Composites. Adv. Funct. Mater. 2016, 26, 4595–4600. (58) Li, J.; Xu, L.; Wang, T.; Song, J.; Chen, J.; Xue, J.; Dong, Y.; Cai, B.; Shan, Q.; Han, B.; Zeng, H. 50-Fold EQE Improvement up to 6.27% of Solution-Processed All-Inorganic Perovskite CsPbBr3 QLEDs via Surface Ligand Density Control. Adv. Mater. 2017, 29, 1603885. (59) Zhang, X.; Liu, H.; Wang, W.; Zhang, J.; Xu, B.; Karen, K. L.; Zheng, Y.; Liu, S.; Chen, S.; Wang, K.; Sun, X. W. Hybrid Perovskite Light-Emitting Diodes Based on Perovskite Nanocrystals with Organic-Inorganic Mixed Cations. Adv. Mater. 2017, 29, 1606405.



(60) Veldhuis, S. A.; Boix, P. P.; Yantara, N.; Li, M.; Sum, T. C.; Mathews, N.; Mhaisalkar, S. G. Perovskite Materials for Light-Emitting Diodes and Lasers. Adv. Mater. 2016, 28, 6804-6834.


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