Direct Evidence of Ion-Migration-Induced Degradation of Ultrabright

Subscriber access provided by WEBSTER UNIV

Organic Electronic Devices

Direct Evidence of Ion-Migration-Induced Degradation of Ultra-Bright Perovskite Light-Emitting Diodes Hyunho Lee, Donghyun Ko, and Changhee Lee ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.8b22217 • Publication Date (Web): 05 Mar 2019 Downloaded from http://pubs.acs.org on March 5, 2019

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 27 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

ACS Applied Materials & Interfaces

Direct Evidence of Ion-Migration-Induced Degradation of Ultra-Bright Perovskite LightEmitting Diodes Hyunho Lee, Donghyun Ko, and Changhee Lee*

Department of Electrical and Computer Engineering, Inter-University Semiconductor Research Center, Seoul National University, Seoul, 08826, Republic of Korea KEYWORDS: perovskite light-emitting diodes, sequential deposition, degradation, ion migration, electrode peel-off

ABSTRACT: Low operational lifetime is a critical issue in perovskite light-emitting diodes. The forward bias currents for light emission accelerate device degradation, which needs to be identified and understood to be able to improve the device stability. Here, we systematically analyse the degradation mechanism of perovskite light-emitting diodes

ACS Paragon Plus Environment

1

ACS Applied Materials & Interfaces 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

Page 2 of 27

(PeLEDs) fabricated with a sequential deposition method which produces compact and pinhole-free perovskite film. The device exhibits an efficient green electroluminescence (peak wavelength at 533 nm and the full-width-half-maximum of 22 nm) with a maximum luminance over 67,000 cd/m2. The lifetime, however, is quite short; under the constant current bias for an initial luminance of 1,000 cd/m2, the decay time to reach half of the initial luminance is approximately 13 min. Dark spots are created and enlarged as a result of perovskite film deterioration and ion migration. By investigating morphological changes in the perovskite films and the amount of ion accumulation under the Al electrode for the unoperated, T50 (luminance decay to 50% of the initial value), and T10 (luminance decay to 10% of the initial value) devices, we propose a degradation mechanism for PeLEDs. The ion migration from the perovskite layer experienced electrochemical interactions with the Al electrode, causing device degradation.

Introduction


2

Page 3 of 27 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


Perovskite light-emitting diodes (PeLEDs) have been emerged as a next generation light sources.

1-4

The high colour purity (electroluminescence (EL) full width at half maximum

(FWHM) < 25 nm) and stoichiometric colour-tuneable characteristics are the most advantageous features over competing EL devices (organic and quantum dot).

PeLEDs have issues in terms of film formation and operational stability that need to be solved. At the early stage of PeLED research, PeLEDs exhibited poor EL performance caused by poor perovskite film morphology.5-6 Pinholes were created inside the perovskite film during perovskite crystallization in the annealing process. Because pinholes act as shunt paths between the electron-transport layer (ETL) and hole-transport layer (HTL), the leakage current of the PeLEDs increased, and the device stability was poor.7 To enhance the quality of the perovskite film, an anti-solvent pinning process was introduced to PeLED fabrication.5 Addition of an anti-solvent (chlorobenzene, chloroform, toluene, or ether) during spin-coating of the perovskite solution ensures pinhole-free perovskite film formation. Based on the improved perovskite film formed by the antisolvent pinning method, PeLEDs with an external quantum efficiency (EQE) over 8% and


3


Page 4 of 27

luminance over 15,000 cd/m2 were reported. However, unlike photovoltaics, the full colour pattern should be defined inside of the pixels for display applications. The anti-solvent pinning process is not applicable to solution-processed patterning methods, such as inkjet printing. Thus, an alternative perovskite film fabrication method to obtain high-quality perovskite films is required. Furthermore, the driving (turn-on) voltage of PeLEDs is approximately 3 V, which implies that a forward bias voltage over 3 V is continuously applied during device operation. Because ion diffusion from the perovskite film during the operation (Vapp < 1.2 V) of perovskite solar cells was reported, ion migration in PeLEDs during device operation is assumed.8-9 The forward bias voltage could accelerate innate ion migration in the perovskite film, resulting in the rapid degradation of the EL performance of the corresponding PeLED. The forward electrical bias causes morphological distortion which reduces the absorbance of perovskite film and creates pinholes.10 The electric field induced ion migration corrodes the electrodes.11 The phase instability of perovskites induces halide separation causing color instability.12,13


4

Page 5 of 27 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


In this report, we fabricated PeLEDs using a sequential deposition method. Sequentially deposited perovskite films show compact and pinhole-free high film quality. The corresponding sequentially deposited perovskite light-emitting diode (SDPeLED) ensures high-performance EL parameters (EQE = 2.15%, luminance = 67,557 cd/m2). Through an in-depth investigation before and after SDPeLED operation, we found direct evidence of SDPeLED degradation. Moreover, we propose an ion-migration-induced degradation mechanism for SDPeLEDs.

RESULTS AND DISCUSSION

Methyl ammonium lead tribromide (MAPbBr3) perovskite thin films were fabricated by a sequential deposition process. The sequential deposition process and one-step deposition process of perovskite films are shown in Figure S1 (Supporting Information). On top of a polyvinylpyrrolidone (PVP)-coated substrate, lead bromide (PbBr2) solution was spin-coated and annealed. Then, methyl ammonium bromide (MABr) solution was sequentially spin-coated and annealed to fabricate a compact and pinhole-free perovskite film.


5


Page 6 of 27

Figure 1. Surface SEM images of sequentially deposited (a) PbBr2 and (b) MAPbBr3. (c) XRD patterns of PbBr2 (black), MABr (blue), MAPbBr3 (red) films on glass, MAPbBr3/PEDOT:PSS on glass (purple) and MAPbBr3 film on top of PEDOT:PSS/PVP-coated substrates (green). d) Cross-sectional SEM image of the SDPeLED. e) Absorbance and photoluminescence spectra of PbBr2 and MAPbBr3.

The morphology of the sequentially deposited perovskite film is shown in Figure 1a and b. The PbBr2 film shows compact and dense film formation (Figure 1a), exhibiting an amorphous state without any crystal peaks in the X-ray diffraction (XRD) pattern (Figure 1c). The MABr spin-coated MAPbBr3 film shows compact and pinholefree film formation (Figure 1b). The size of the perovskite grains was less than 50 nm. For PeLEDs, grain size should be less than 100 nm to facilitate efficient radiative


6

Page 7 of 27 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


bimolecular recombination.5, 14 The exciton binding energy of perovskite is very low, even excitons thermally generate free charge carriers at room temperature.15-16 Because the electron-hole diffusion length of perovskite is approximately 100 nm, a grain size less than 100 nm confines charge carriers effectively.17 The diffusion length of charge carriers is confined with smaller grains and reduces the non-radiative recombination. Thus, the small grain size of the sequentially deposited perovskite film induces a high radiative electron-hole binding rate. XRD shows the crystallinity of the sequentially deposited perovskite film (Figure 1c and Figure S2, Supporting Information). The diffraction peak at 17.29° in the case of MAPbBr3 film on the glass is a novel crystalline diffraction peak which is supposed to be evidence of the sequentially deposited perovskite film. The diffraction peak at 17.29° originates from one of the main diffraction peaks of the MABr film on glass. The perovskite film on the HTL (PEDOT:PSS and PVP) shows no diffraction peak at 17.29° which indicates the perovskite film formation on the HTL was improved without any excess compounds. The diffraction peaks of MAPbBr3 on PVP, PEDOT:PSS, and glass at 14.98°, 30.19°, and 33.80° correspond to (001), (002), and (021) plane orientations, which indicate pure cubic MAPbBr3 phases.18


7


Page 8 of 27

Cross-sectional scanning electron microscopy (SEM) confirms the formation of a compact and pinhole-free perovskite film as shown in Figure 1d and Figure S3 (Supporting Information). Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) acts as a HTL, and a very thin (~5 nm) PVP layer was inserted to prevent strong optoelectronic quenching by the PEDOT:PSS layer. A bulk MAPbBr3 perovskite layer was used as the emission layer, and TPBi acts as an ETL. Finally, lithium fluoride (LiF) and Al were evaporated. The PbBr2 film has very low absorbance, while the MAPbBr3 film has an absorbance peak at 515 nm, with increasing absorbance as the photon energy increases. Along with the absorbance peak, sharp photoluminescence (PL) at 546 nm was measured (Figure 1e). The PL spectra of the PVP-inserted devices showed a much higher intensity than those for the devices without PVP (Figure S4, Supporting Information). Strong non-radiative quenching by PEDOT:PSS was suppressed by inserting the PVP layer, which promises the enhanced EL performance. We optimized the concentration of each PbBr2 and MABr solution with respect to the film morphology. The sequentially deposited perovskite film morphology


8

Page 9 of 27 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


and absorbance depend on the solution concentration, as shown in Figure S5~S8 (Supporting Information).

Figure 2. (a) J-V curves of the SDPeLED. (b) and (c) Luminance and CE (EQE) graphs of the SDPeLED with respect to current density. (d) Operation image of a large-area (1 cm2) SDPeLED. (e) EL spectra of the SDPeLED.

Table 1. Device performances of the SDPeLED.


9


MAPbBr3

Average (Best)

Max. CE

Max. EQE

(cd/A)

(%)

5.72 ± 1.88

1.34 ± 0.43

(9.32)

(2.15)

Max. Luminance (cd/m2)

34,010 ± 19,675

Page 10 of 27

Peak Wavelength (nm)

533

(67,557)

The EL performance of a SDPeLED is shown in Figure 2. Current density– voltage plot of SDPeLED is shown in Figure 2a. The luminance of the SDPeLED continuously increases as the current density increases (Figure 2b). The maximum luminance of the SDPeLED was 67,557 cd/m2. The SDPeLED shows efficient EL performance with a maximum current efficiency (CE) of 9.32 cd/A and maximum EQE of 2.15% (Figure 2c). The statistic distribution of device performance is shown in Figure S9 (Supporting Information). Moreover, the efficiency roll-off from the maximum efficiency point (500 mA/cm2) to 1,000 mA/cm2 was very low. Figure 2d is the operation image of the SDPeLED under 100 mA/cm2 current bias. The EL peak was located at 533 nm, and the FWHM of the peak was 22 nm (Figure 2e). The EL performance of SDPeLED is


10

Page 11 of 27 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


summarized in Table 1. For optimization of the EL performance, we controlled the solution concentration of PbBr2 (Figure S10 and Table S1, Supporting Information) and MABr (Figure S11 and Table S2, Supporting Information), the solution concentration of PVP (Figure S12 and Table S3, Supporting Information), and the annealing time of the perovskite film (Figure S13 and Table S4, Supporting Information).

Figure 3. (a) Luminance decay graph of the SDPeLED. The initial luminance of the device was 1,000 cd/m2. The applied current was 1.0 mA. (b) The applied voltage


11


Page 12 of 27

influenced the device degradation. (c) CIE coordinate plot with respect to the device operation time. (d) Time-dependent dark spot area growth. (e) Real-time luminance degradation image. The initial luminance of the fresh device was 1,000 cd/m2.

We investigated the operational device stability of SDPeLEDs as shown in Figure 3. We operated an SDPeLED and measured the lifetime under L0 (initial luminance) = 1,000 cd/m2. Luminance decay under a constant current bias was observed with an increase in applied voltage (Figure 3a and b). The half-lifetime (T50) of luminance under 1,000 cd/m2 was 13 min, and the applied voltage increased from 4.2 V to 4.8 V during device operation. The power applied to the device during device operation continuously increased. This implies that the applied Joule heat per area continuously increased.19 Thus, an increase in the power load to the light-emitting diode is speculated to accelerate device degradation. Moreover, we found a shift in the colour coordinate CIE X, Y upon device degradation (Figure 3c). The fresh device exhibited CIE X, Y (0.199, 0.763). After 90% decay of the initial luminance (T10), the colour coordinate shifted to


12

Page 13 of 27 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


CIE X, Y (0.205, 0.756). The colour coordinate shift can be a critical issue for display applications because colour instability breaks the balance among the red, green, and blue pixels to form a white colour. Magnified operation images of the SDPeLED during operation under L0 = 1,000 cd/m2 are shown in Figure 3e. The large green emission areas gradually turned into black spots (Figure 3d).

Figure 4. (a)-(c) TOF-SIMS depth profile for unoperated, T50, and T10 devices, respectively. (d) Ion distribution of Br- with respect to degradation time. (e) Ion


13


Page 14 of 27

distribution of CN- (MA+) with respect to degradation time. (f) 3D images of Br- and CN(MA+) ion migration from the TOF-SIMS depth profile. The length of each axis is 70 μm.

To investigate the distributional change in elements with respect to device degradation, the depth profiles of time-of-flight secondary ion mass spectrometry (TOFSIMS) were investigated (Figure 4). Each layer of the SDPeLED has distinguishable representative elements. The Al- ion represents the Al electrode, the Li- ion represents LiF, the CH- ion represents TPBi and PVP, the Br-, Br2- and Pb- ions represent perovskite, the SO2- ion represents PEDOT:PSS, and the In2O2- ion represents indium tin oxide (ITO). A perceivable layer boundary for each SDPeLED constituent layer was constructed (Figure 4a~c). The distribution of Br2- ions is plotted to support the distribution of Br- ions because the intensity of Br- ions was too strong and beyond upper limit of detection. Depending on the degradation time, some elements showed a distinct distributional change. Figure 4d and e represent the TOF-SIMS graphs of Brand CN- ions. The CN- ion is the distinctive ion representing the MA+ ion in the


14

Page 15 of 27 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


perovskite.20-21 As the device operation time increases, the ion concentration of Br- and CN- (MA+) inside of the Al electrode (sputter time 0~400 s) increased continuously. Since both Br- and CN- (MA+) ions are distinctive ions for the perovskite layer, this indicates that the perovskite is decomposed and the ions are migrated from the perovskite layer to the Al electrode as a result of device degradation. The constant current bias through the entire device produces local heat which accelerate perovskite decomposition.21 The decomposed ions have selective and directional migration to the Al electrode. The forward biased current drifts MA+ ions toward the Al electrode under the device operation while the concentration of Br- ions increases among the perovskite layer. The compositional gradient of Br- ions induces ion diffusion from perovskite layer to the Al electrode. The highly reactive metal-halide interaction stimulates Br- ion diffusion from the perovskite layer to the Al electrode.22 For more details, the depth profiles of the Br- and CN- (MA+) ions are plotted in the 3D image in Figure 4f. The 3D Br- and CN- (MA+) ion distributions in the device clearly show that the Br- and CN- (MA+) ions migrate from the perovskite layer to the Al electrode as a result of device degradation. We also checked the 3D map of depth profiles for CH- ions because there


15


Page 16 of 27

is possibility that CN- signal come from TPBi (Figure S14, Supporting Information). We found almost negligible CH- ion migration after the device operation. Thus, we believe that there was almost no ion migration from the TPBi layer. Small amount of CH- ion migration on the 3D map indicates that CH- ion also take a minor part in detecting MA+ ions. Moreover, Br- and CN- (MA+) migration paths were created as a result of device degradation. The sizes of the created ion migration paths (25 μm) are similar to the size of the dark spot in Figure 3e. The creation of Br- and CN- (MA+) migration paths is speculated to cause the dark spots in the emission area. Thus, the migration of Br- and CN- (MA+) ions can be considered as direct evidence of SDPeLED degradation.


16

Page 17 of 27 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


Figure 5. Ion distribution counts in the TOF-SIMS surface profile of the peeled-off Al electrodes.

In our previous report, we found that the highly reactive metal-halide interaction induces more ion diffusion from the perovskite film, which accelerates degradation of the perovskite solar cells.8 Analysis of the peeled-off electrode allowed the efficient investigation of the degradation mechanism of perovskite solar cells.8, 21 The diffused ions reacted with the metal electrode and created metal-halide compounds or


17


Page 18 of 27

accumulated halide ion by-products. The experimental scheme for peeling off the Al electrode is shown in Figure S15 (Supporting Information). Figure S15b and c (Supporting Information) are the magnified images of the peeled-off Al electrode for the unoperated and T10 devices. For the red centered area (100 μm × 100 μm), the TOFSIMS surface profiling of the peeled-off Al electrode was conducted. Because the surface of the Al electrodes was very rough and had many wrinkles, we normalized the detected Al elements of both samples for quantitative comparison. The comparison of Br- and CN- (MA+) ions in the unoperated and T10 electrodes indicates that both ions were migrated much more after device operation, as shown in Figure 5. The forward bias operation of SDPeLED accelerated ion migration from the light-emission layer to the Al electrode, resulting in rapid luminance decay of the SDPeLED. The ion migration from the perovskite layer indicates that the chemical structure of the perovskite was partially deteriorated. This implies the possibility of morphological distortion of the perovskite film. To investigate morphological changes upon device operation, the TPBi film was washed away after the Al electrode was peeled off. After the Al electrode was peeled off, the device was dipped into chloroform (CF) solvent for 30 s (Figure S16,


18

Page 19 of 27 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


Supporting Information). This method of dissolving the organic layer is very mild and does no physical damage to the underlying perovskite film (Figure S17, Supporting Information).21 The initial perovskite film shows very compact and dense film formation (Figure 6a). Figure 6b shows the morphology of the T10 perovskite film beneath the TPBi layer and Al electrode. The perovskite grains aggregated (grain size larger than 100 nm), and pinholes were created. These pinholes act as shunt paths between PEDOT:PSS and TPBi, which are shown as dark spots in the luminance image and reduce the EL performance. Thus, ion migration upon device degradation induces morphological distortion of the perovskite film, resulting in the aggregation of perovskite grains, increased perovskite grain size, and the creation of pinholes.


19


Page 20 of 27

Figure 6. (a) SEM image of the fresh perovskite film. (b) SEM image of the perovskite film from the T10 device. For the T10 SDPeLED, the Al electrode was peeled off, and TPBi was washed away by dipping the substrate in CF. (c) Ion-migration-induced degradation mechanism of the SDPeLED. The red and blue dots indicate Br- and MA+ ions.


20

Page 21 of 27 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


Based on the aforementioned observations, we found direct evidence of SDPeLED degradation under a constant current bias. Device operation under a forward bias of over 3 V accelerated ion migration from the perovskite layer, which caused the distortion of the perovskite morphology. Figure 6c shows the degradation mechanism of SDPeLEDs. With the innate ion migration from the perovskite layer to the Al electrode, the perovskite film underwent morphological distortion. The aggregated grains might prohibit efficient radiative electron-hole recombination, which decreases the EL performance. The constant current bias induced more aggregated perovskite grains and pinholes, which further decreased EL performance. As a result of the ion migration, migration paths for Br- and MA+ were created, which were the origins of the dark spots on the SDPeLEDs.

Conclusion

We optimized a sequential deposition method to fabricate perovskite films. Concentration of solutions and annealing time of perovskite films were precisely controlled. The sequentially deposited perovskite layer was compact and pinhole-free.


21


Page 22 of 27

From this high-quality perovskite film, we fabricated very efficient and pure-coloured PeLEDs (CE: 9.32 cd/A, EQE: 2.15 %). Moreover, we found direct evidence of SDPeLED degradation. Ions migration from the perovskite layer experienced electrochemical interactions with the Al electrode during device degradation. The perovskite films were deteriorated, and pinholes were created. In particular, these pinholes cause leakage currents and dark spots, accelerating device degradation. Based on these observations, we proposed an ion-migration-induced degradation mechanism of SDPeLEDs. The result provides an insight for improving the performance and stability of PeLEDs with improved perovskite film quality.


22

Page 23 of 27 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


ASSOCIATED CONTENT Supporting Information. Experimental details; PL of perovskite films on different substrates; SEM image of sequentially deposited perovskite films; Absorbance of perovskite films; EL performance of different conditions of perovskite films; Tables of performance of different conditions of perovskite films. AUTHOR INFORMATION

Corresponding Author *Email: [email protected]

Author Contributions The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript.

Notes The authors declare no competing financial interest.


23


Page 24 of 27

ACKNOWLEDGMENT This work is supported by the Mid-career Researcher Program (2016R1A2B3009301) funded by the National Research Foundation of Korea (NRF).

REFERENCES (1) 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. (2) Zhao, B.; Bai, S.; Kim, V.; Lamboll, R.; Shivanna, R.; Auras, F.; Richter, J. M.; Yang, L.; Dai, L.; Alsari, M.; She, X.-J.; Liang, L.; Zhang, J.; Lilliu, S.; Gao, P.; Snaith, H. J.; Wang, J.; Greenham, N. C.; Friend, R. H.; Di, D. High-efficiency perovskite–polymer bulk heterostructure light-emitting diodes. Nat. Photonics 2018, 12, 783-789. (3) Cao, Y.; Wang, N.; Tian, H.; Guo, J.; Wei, Y.; Chen, H.; Miao, Y.; Zou, W.; Pan, K.; He, Y.; Cao, H.; Ke, Y.; Xu, M.; Wang, Y.; Yang, M.; Du, K.; Fu, Z.; Kong, D.; Dai, D.; Jin, Y.; Li, G.; Li, H.; Peng, Q.; Wang, J.; Huang, W. Perovskite light-emitting diodes based on spontaneously formed submicrometre-scale structures. Nature 2018, 562, 249-253. (4) Lin, K.; Xing, J.; Quan, L. N.; de Arquer, F. P. G.; Gong, X.; Lu, J.; Xie, L.; Zhao, W.; Zhang, D.; Yan, C.; Li, W.; Liu, X.; Lu, Y.; Kirman, J.; Sargent, E. H.; Xiong, Q.; Wei, Z. Perovskite light-emitting diodes with external quantum efficiency exceeding 20 per cent.

Nature 2018, 562, 245-248. (5) 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.


24

Page 25 of 27 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


(6) 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, 27, 1248-1254. (7) Eperon, G. E.; Burlakov, V. M.; Docampo, P.; Goriely, A.; Snaith, H. J. Morphological Control for High Performance, Solution-Processed Planar Heterojunction Perovskite Solar Cells. Adv. Funct. Mater. 2014, 24, 151-157. (8) Lee, H.; Lee, C. Analysis of Ion‐Diffusion‐Induced Interface Degradation in Inverted Perovskite Solar Cells via Restoration of the Ag Electrode. Adv. Energy Mater. 2018, 8, 1702197. (9) Eames, C.; Frost, J. M.; Barnes, P. R. F.; O’Regan, B. C.; Walsh, A.; Islam, M. S. Ionic transport in hybrid lead iodide perovskite solar cells. Nat. Commun. 2015, 6, 7497. (10) Xu, B.; Wang, W.; Zhang, X.; Liu, H.; Zhang, Y.; Mei, G.; Chen, S.; Wang, K.; Wang, L.; Sun, X. W. Electric Bias Induced Degradation in Organic-Inorganic Hybrid Perovskite Light-Emitting Diodes. Sci. Rep. 2018, 8, 15799. (11) Lee, S.; Park, J. H.; Lee, B. R.; Jung, E. D.; Yu, J. C.; Di Nuzzo, D.; Friend, R. H.; Song, M. H. Amine-Based Passivating Materials for Enhanced Optical Properties and Performance of Organic–Inorganic Perovskites in Light-Emitting Diodes. J. Phys. Chem.

Lett. 2017, 8, 1784-1792. (12) Vashishtha, P.; Halpert, J. E. Field-Driven Ion Migration and Color Instability in Red-Emitting Mixed Halide Perovskite Nanocrystal Light-Emitting Diodes. Chem. Mater. 2017, 29, 5965-5973. (13) Bischak, C. G.; Hetherington, C. L.; Wu, H.; Aloni, S.; Ogletree, D. F.; Limmer, D. T.; Ginsberg, N. S. Origin of Reversible Photoinduced Phase Separation in Hybrid Perovskites. Nano Lett. 2017, 17, 1028-1033. (14) Xiao, Z.; Kerner, R. A.; Zhao, L.; Tran, N. L.; Lee, K. M.; Koh, T.-W.; Scholes, G. D.; Rand, B. P. Efficient perovskite light-emitting diodes featuring nanometre-sized crystallites. Nat. Photonics 2017, 11, 108-115. (15) Miyata, A.; Mitioglu, A.; Plochocka, P.; Portugall, O.; Wang, J. T.-W.; Stranks, S. D.; Snaith, H. J.; Nicholas, R. J. Direct measurement of the exciton binding energy and effective masses for charge carriers in organic–inorganic tri-halide perovskites. Nat.

Phys. 2015, 11, 582-587.


25


Page 26 of 27

(16) Yang, Z.; Surrente, A.; Galkowski, K.; Bruyant, N.; Maude, D. K.; Haghighirad, A. A.; Snaith, H. J.; Plochocka, P.; Nicholas, R. J. Unraveling the Exciton Binding Energy and the Dielectric Constant in Single-Crystal Methylammonium Lead Triiodide Perovskite. J. Phys. Chem. Lett. 2017, 8, 1851-1855. (17) Adhyaksa, G. W. P.; Veldhuizen, L. W.; Kuang, Y.; Brittman, S.; Schropp, R. E. I.; Garnett, E. C. Carrier Diffusion Lengths in Hybrid Perovskites: Processing, Composition, Aging, and Surface Passivation Effects. Chem. Mater. 2016, 28, 52595263. (18) Zhu, H.; Fu, Y.; Meng, F.; Wu, X.; Gong, Z.; Ding, Q.; Gustafsson, M. V.; Trinh, M. T.; Jin, S.; Zhu, X. Y. Lead halide perovskite nanowire lasers with low lasing thresholds and high quality factors. Nat. Mater. 2015, 14, 636-642. (19) Gärditz, C.; Winnacker, A.; Schindler, F.; Paetzold, R. Impact of Joule heating on the brightness homogeneity of organic light emitting devices. Appl. Phys. Lett. 2007, 90, 103506. (20) Guerrero, A.; You, J.; Aranda, C.; Kang, Y. S.; Garcia-Belmonte, G.; Zhou, H.; Bisquert, J.; Yang, Y. Interfacial Degradation of Planar Lead Halide Perovskite Solar Cells. ACS Nano 2016, 10, 218-224. (21) Li, J.; Dong, Q.; Li, N.; Wang, L. Direct Evidence of Ion Diffusion for the SilverElectrode-Induced Thermal Degradation of Inverted Perovskite Solar Cells. Adv. Energy

Mater. 2017, 7, 1602922. (22) Uno, T.; Tatsumi, K. Thermal reliability of gold–aluminum bonds encapsulated in biphenyl epoxy resin. Microelectron. Reliab. 2000, 40, 145-153.


26

Page 27 of 27 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


Table of Contents


27

Direct Evidence of Ion-Migration-Induced Degradation of Ultrabright

Recommend Documents