Heat Treatment for Regenerating the Degraded Low Dimensional

Subscriber access provided by READING UNIV

Article

Heat Treatment for Regenerating the Degraded Low Dimensional Perovskite Solar Cells Chunqing Ma, Dong Shen, Jian Qing, Tsz-Wai Ng, Ming-Fai Lo, and Chun-Sing Lee ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.7b15059 • Publication Date (Web): 29 Dec 2017 Downloaded from http://pubs.acs.org on December 31, 2017

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 free 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 accessible to all readers and 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.

ACS Applied Materials & Interfaces 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 19 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

Heat Treatment for Regenerating the Degraded Low Dimensional Perovskite Solar Cells Chunqing Ma,ab Dong Shen,ab Jian Qing,ab Tsz-Wai Ng,ab Ming-Fai Lo,ab* Chun-Sing Leeab*

a

Center of Super-Diamond and Advanced Films (COSDAF) and Department of Chemistry, City

University of Hong Kong, Hong Kong SAR, P. R. China b

City University of Hong Kong Shenzhen Research Institute, Shenzhen 518057, Guangdong, P.R.

China

KEYWORDS: heat treatment, stability, degradation, low dimension, perovskite solar cell

ABSTRACT Organolead halide perovskite devices are reported to be susceptible to thermal degradation, which is resulted from heat induced fast ion diffusion and structural decomposition. In this work, it is found that performances of degraded low dimensional perovskite solar cells can be considerably improved (e. g. power conversion efficiency shows ~ 10% increase over the fresh device) by a short time heat treatment (85oC, 3 mins). Capacitance-Frequency, X-ray diffraction and ionic diffusion calculation results suggest that heat treatment can enhance the crystallinity of the degraded low dimensional perovskite and minimize the detrimental effects caused by the water molecules, leading to improved performances. Our results indicate that the heat treatment does not necessarily lead to the accelerated degradation, but can also regenerate the degraded low dimensional perovskite. 1

ACS Paragon Plus Environment

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 19

Introduction Organolead halide perovskite solar cells (PSCs) are the front-runners in the field of photovoltaics and lead to record breaking efficiencies.1-7 Solution processability is one of the major advantages of perovskite materials, which require only a simple heat treatment (60-100oC) to convert the precursor solution to the crystalline perovskite film due to the low formation energies.8-9 However, the low formation energies also make perovskite materials susceptible to high temperature (e. g. 85oC), as stuctural decomposition might be initiated at 85oC which is close to the formation temperature. In 2014, Katz et al. reported that the heat treatment can accelerate the degradation of perovskite during operation.10 In 2017, Liu et al. reported that significant decomposition occurs during heating a low dimensional (LD) perovskite at 80°C.11 Structural and chemical changes are usually observed due to heat-induced ion diffuison.12-18 The pervious studies support the view that high temperature is harmful to a perovskite device, which can induce the fast ion diffusion and structural decomposition. In this work, we show that instead of the commonly observed “heat accelerated degradation”, a short time heat treatment (85oC, 3 mins) can regenerate the moisture-affected LD PSCs. Our results show that the performances of degraded LD ((BA)2(MA)3(Pb0.75Sn0.25)4I13) perovskite devices can be rapidly improved upon a short time heat treatment. Capacitance-Frequency (CF), X-ray diffraction (XRD) and ionic diffusion calculation results suggest that the heat treatment applied on the moisture-affected LD perovskites can (1) remove the water molecules meanwhile avoid evaporation of the methylamine ions and; (2) simultaneously enhance the crystallinity of the perovskites, leading to overall improved performances. Surprisingly, the power conversion efficiency (PCE) of the regenerated device shows 10% higher than its original value by this heat treatment. 2


Page 3 of 19 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


Results and discussion Crystal structures of the 3D and the LD Pb-Sn halide perovskites, MAPb0.75Sn0.25I3 and (BA)2(MA)3(Pb0.75Sn0.25)4I13 (n=4), are illustrated in Figure 1a. Generally, in the LD perovskite, the insulating organic BA cations isolate the conducting inorganic slabs from one to another, which significantly hinder the charge transport within the perovskite film, leading to a poor efficiency. However, this poor charge transport can be greatly offset if the LD layers are aligned with the current flow.19

Figure 1. (a) Crystal structures of the MAPb0.75Sn0.25I3 (3D) and the (BA)2(MA)3(Pb0.75Sn0.25)4I13 (LD) perovskites. (b) XRD patterns of the 3D and the LD perovskite films. (c) J-V characteristics of corresponding PSCs. 3



Page 4 of 19

To endow the LD perovskite with a highly oriented crystal structure, a MACl-assisted one-step method was employed to facilitate the directional growth of perovskite (see Methods for details).20 XRD patterns of the as-prepared 3D and LD perovskites are shown in Figure 1b. Only two diffraction peaks at 14.2 and 28.6° are observed for the LD perovskite, which is attributed to the (111) and (222) crystal plane, respectively, and the absence of (0k0) diffraction peak demonstrates the highly preferred crystal orientation of the LD perovskite.21 The absorption spectrum (Figure S1a) of the LD perovskite film shows an exciton absorption peak around 660 nm, which confirms the formation of LD perovskite (n=4).22-23 Based on the as-prepared perovskite, we fabricated PSCs with a device configuration of ITO/PEDOT:PSS/perovskite/C60/BCP/Ag, and their photovoltaic performances were evaluated. Heating time of the LD perovskite film during the synthesis process is optimized, as illustrated in Figure S2 and Table S1. It is recorded that device based on the 3D MAPb0.75Sn0.25I3 perovskite achieves a PCE of 13.1%, with a open-circuit voltage (Voc) of 0.74 V, a short-circuit current (Jsc) of 25.3 mA cm-2 and a fill factor (FF) of 69.8%. For LD (BA)2(MA)3(Pb0.75Sn0.25)4I13 PSCs, a champion PCE of 11.2% is achieved, with a Voc of 0.80 V, a

Jsc of 19.8 mA cm-2 and a FF of 71.0%. The high PCE of the LD PSC is attributed to the excellent crystallinity and highly preferred orientation of LD perovskite film. External quantum efficiency (EQE) of the PSCs and statistics of PCEs based on 25 devices are illustrated in Figure S1, which further confirms reproducibility of the high efficiency achieved above. To study the effects of heat treatment on moisture-affected perovskite, PCE of LD PSCs under 1 Sun AM1.5G illumination at a relative humidity (RH) of 85 ± 5% are continuously monitored (Figure 2). The illumination and measurement are temporarily suspended when the PCE degrades by 4


Page 5 of 19 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


10, 20, 50 and 70%. The devices are then heat treated at 85oC for 3 minutes in dark (represented by the vertical bars in Figure 2). This heat treatment condition shows the strongest regeneration effect, as shown in Figure S3 and Table S2. The illumination and PCE measurement are then resumed. Interestingly, the PCE of devices with 10%, 20% and 50% degradation (Figure 2a-c) can greatly improve to 10% higher than the initial PCE (i.e. Time = 0 min). After the device’s PCE degrades by 70% (Figure 2d), the degraded PCE can no longer recover to its original value, suggesting that the device has already suffered from permanent damages. In contrast, PCE of the 3D PSC shows a sharp drop upon a same heat treatment (Figure S4).

5



Page 6 of 19

Figure 2. Time evolution of the PCE of LD perovskite devices under constant illumination (1 Sun). After the PCE degraded by ~ (a) 10, (b) 20, (c) 50 and (d) 70% (represented by dot line), the two solar cells are heated at 85oC for 3 minutes in dark (represented by red vertical bars) and then put back to the illumination and measurement system, the improved PCE (~10% higher than the original value) is represented by shade area. The temperature of the sample under constant illumination is also shown in Figure S5.

6


Page 7 of 19 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


To further check whether the PCE improvement of a degraded device is a one-off phenomenon, the same heat treatment is applied twice on a LD PSC after 50% PCE degradation for each cycle. PCE, Jsc, Voc and FF of the device are shown in Figure S6. Obviously, after the two cycles of degradation, all these parameters can improve to higher values upon heat treatment. Furthermore, a same heat treatment-induced regeneration effect is observed on a PEA2MA3Pb4I13 solar cell (Figure S7). Based on these results, we can conclude that the performances of degraded LD perovskite devices can be enhanced by a short time heat treatment. To the best of our knowledge, such heat treatment-induced regeneration effect has not been observed in organometallic halide PSCs. We also do a control experiment in which the illumination and measurement on a LD PSC is simply suspended for 3 minutes with no heat treatment after its PCE drops to 75% of its original value (Figure S8). After resting in dark, the Voc and FF show negligible regeneration while a small recovery can be seen in the Jsc. In fact, such mild Jsc recovery has been reported by Nie et al, and is attributed to the light-activated meta-stable deep-level trap states.24-25

7



Page 8 of 19

Figure 3. Evidence and characterization of the regeneration process. (a) CF plots of LD PSC during degradation and heat treatment. (b) (111) XRD peak of LD perovskite upon air exposure and heat treatment. (c) Arrhenius-like plot of ln[1/(T·Tw)] vs 1/T for 3D and LD PSCs.

To further investigate this interesting effect induced by the heat treatment, we carry out CF analysis of a LD PSC and analyze the structural changes with XRD. Figure 3a illustrates the CF profile measured using electrochemical impedance spectroscopy (EIS). The low frequency capacitance (value measured at 1 Hz) is used to analyze the water absorption process.26 The low-frequency capacitance increases from 3.7×10-7 F in the freshly prepared device (black) to 5.6×10-7 F after a 1.5 8


Page 9 of 19 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


h exposure (blue) to ambient air (RH ~85%) in dark. This has been attributed to water absorption, which forms an ionic double-layer, leading to the increase in the capacitance.27 Interestingly, after heat treatment at 85oC for 3 minutes, the capacitance decreases to 3.8×10-7 F, which is comparable to the original value. This indicates that the water absorption process is reversible by a heat treatment. It was reported that the MAPbI3 • H2O phase, formed by the hydration reaction during the degradation process, can be fully reversed by exposing to a dry environment.28-29 Here, we found that except the dry air, a suitable heat treatment can effectively minimize detrimental effects caused by water molecules. Variations in crystal structure of moisture-affected perovskite films upon heat treatment are investigated with XRD. Figure 3b shows that intensity of the (111) peak of the pristine sample (black line) decreases upon air exposure (red line). The full XRD patterns are also shown in Figure S9. It is consistent with the above CF analysis as water molecules can form hydrogen bond with MA+ and weaken the bond between MA+ and PbI6 octahedron, leading to a decreased crystallinity.30-34 The XRD peak of the heat treated sample shows the highest intensity in Figure 3b. This suggests that the heat treatment can heal the damage and further enhance the crystallinity of the degraded LD perovskite film. However, it is noted that the heat treatment can no longer fully heal the damage if the film is “over” degraded. For a LD perovskite film after 12 hours air exposure, the same heat treatment can only partially heal the damage (Figure S10). This is in consistent with the observation of incomplete PCE regeneration in the LD PSC after its PCE degraded by 70% (Figure 2d). The XRD patterns of the LD and 3D perovskite under high humidity with different air exposure times are shown in Figure S11. The XRD patterns of “over” degraded 3D perovskite exhibit two strong diffractive peaks at 2θ = 10.5° and 2θ = 11.4°, which can be ascribed to the formation of 9



Page 10 of 19

dihydrated perovskite. For LD perovskite, the dihydrate peak is only barely observable after 4 days of air exposure. The absorption spectra also show the same results as the XRD (Figure S12). Based on these results, we can conclude that a short time heat treatment can be beneficial to degraded LD perovskite devices, which is different from previous reports that heat treatment can accelerate the degradation of perovskite devices. For comparison, we carry out the same XRD analysis on a 3D perovskite film deposited on ITO-coated glass (Figure S13). As expected, the (110) peak intensity decrease upon air exposure. The same heat treatment causes further degradation instead of regeneration. This can be explained by the high temperature induced fast ion diffusion, which seriously damages the crystal structure of 3D perovskite.35-36 To analyze the influences of heat treatment on the LD and the 3D perovskites, we follow the EIS approach of Bag et al.37 They pointed out that thermal-induced alkyl ammonium ion diffusion activation energies (Ea) can be calculated with the following equation:

=

exp (

)

(1),

where Warburg time constant, TW, is obtained by fitting EIS results at various temperatures (Figure S14). k is temperature, h is Planck’s constant, LD is effective ion diffusion length, a is the lattice parameter, α is the coordination factor. By plotting ln[1/(T·Tw)] vs 1/T (Figure 3c), the Ea of the 3D perovskite at the low (320 K) temperature region is determined to be 56 kJ·mol-1 and 13 kJ· mol-1, respectively, which is similar to the result of De Angelis et al.38-39 The different activation energies at different temperature regions are attributed to phase transition. Interestingly, in the case of LD perovskite, the same Ea of 77 kJ· mol-1 is obtained at all temperatures, suggesting the temperature-dependent phase transition does not occur in the LD 10


Page 11 of 19 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. Moreover, the activation energy of alkyl ammonium ion diffusion in the 3D perovskite is much lower than that in the LD perovskite, which strongly demonstrates that alkyl ammonium ions can diffuse much more easily in the 3D perovskite. As is known, ion diffusion within perovskite will break the crystal structure, and thus causes irreversible degradation. We conclude from these results that the long chain BA cations can retard the ion diffusion induced by heat. Thus, the LD perovskite is much more stable under high temperature. To further confirm the thermal stability, the effects of the high temperature on the device performance and structure of the LD and the 3D perovskite are also studied (Figure S15). It can be clearly observed that high temperature can cause performance degradation in both LD and 3D PSCs with the LD perovskite shows a much slower degradation compared to the 3D counterpart, which is consistent with the EIS results. To explain the above experimental results, we propose a mechanism based on moisture-induced degradation. Under high humidity (RH of 85 ± 5%), there are abundant water molecules around the perovskite, which can diffuse into the lattice and form dihydrated perovskite, leading to degradation. Annealing of the moisture-affected 3D perovskite will lead to substantially increased ion diffusion because of the lattice changes (Figure 3d). This will lead to further reduced crystallinity. In LD perovskite, the crystals are protected by hydrophobic organic long chain. This suggests that it is much more difficult for water molecules to get into the perovskite to form dihydrates, which is irreversible (shown in Figure S11). On the other hand, the much higher Ea of the LD perovskite suggests a much lower rate of ion diffusion, leading to a stable structure under high temperature. Thus, the mild annealing allows evaporation of the water molecules and simultaneously enhance the crystallinity, leading to improved performances. However, if the LD perovskite is exposed to air for

11



Page 12 of 19

too long, some water molecules would react with the perovskite and form dihydrates. Beyond this point, the moisture-induced degradation can no longer be fully recovered. Conclusions In conclusion, we have investigated the influences of heat treatment on degraded LD perovskite devices. It is found that a short time heat treatment can enhance the crystallinity and device performance of degraded LD perovskites, which is different from previous reports that heat treatment can accelerate the degradation of perovskites. LD perovskite is shown to have better stabilities under high humidity and high temperature compared to the 3D perovskite. Therefore, a short time heat treatment can evaporate the water molecules and meanwhile enhance the crystallinity of the LD perovskites. This simple heat treatment not only suggests viable approaches for developing stable perovskite devices but also extends the applications of the heat treatment.

Experimental Methods Perovskite Precursor Solution Preparation and Device Fabrication. The perovskite solutions were prepared by mixing MAI (Lumtech) and BAI (Lumtech) with 0.75 mmol of lead iodide (Sigma-Aldrich), 0.25 mmol of tin iodide (Sigma-Aldrich), 0.1 mmol of MACl (Lumtech) in 1 mL of anhydrous N,N-dimethylformamide (Sigma-Aldrich) and 1 mmol of dimethylsulfoxide (Sigma-Aldrich). The solutions were stirred at room temperature overnight. The perovskite films are prepared by spin-coating the solution at 4000 rpm followed by solvent annealing at 100°C for 10 min. Solar cells with a configuration of ITO/PEDOT:PSS/perovskite/C60 (20 nm)/BCP(8 nm)/Ag were fabricated as we reported before, while the organic layer prepared by thermal evaporation.40 12


Page 13 of 19 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


Characterization. Scanning electron microscope images were recorded with a Philips XL30 FEG SEM. XRD measurements were obtained by a Philips X’ Pert diffractometer with Cu Kα radiation. X-ray photoelectron spectra were recorded with Physical Electronics PHI5802 using Al mono excitation source. J-V curves of the PSCs were measured at 100 mW cm-2 using an Oriel 150 W solar simulator. EIS measurements were carried out with a ZAHNER IM6 workstation.

ASSOCIATED CONTENT Supporting Information. Absorption spectra of 3D and LD perovskite films; EQE spectra of 3D and LD PSCs; Histogram of PCEs based on 25 LD PSCs; JV curves and photovoltaic parameters of LD PSCs heated at 100oC for 6, 8, 10, 12, 15 mins during synthesis process; JV curves and photovoltaic parameters of 10% degraded LD PSCs after different heat treatment process Heat treatment (85oC, 3 mins) on a 3D PSC after degraded by 10%; The temperature of the sample under constant illumination; Variations of PCE Jsc, Voc and FF of LD PSCs during 2-cycles of degradation/heat treatment; Heat treatment (85oC, 3 mins) of LD PEA2MA3Pb4I13 PSC after degraded by 10%; Time evolution of LD PSCs performance under constant 1-sun illumination and after resting the device in dark; XRD patterns of LD perovskite upon air exposure and heat treatment; XRD patterns of LD perovskite film after 12 h degradation and heat treatment; XRD patterns of 3D and LD perovskite film with different air exposure times; Absorption spectra of LD perovskite film after degradation and heat treatment; XRD patterns of 3D perovskite film after 3 h degradation and heat treatment; EIS plot and fitting result of 3D and LD PSCs; Cross-section SEM

13



Page 14 of 19

images of (c) 3D and (d) LD perovskite; Degradation process of 3D and LD perovskite without encapsulation under continous heating at 85○C. AUTHOR INFORMATION Corresponding Author * E-mail: [email protected]. * E-mail: [email protected].

Acknowledgement This work was supported by Research Grants Council of the Hong Kong Special Administrative Region, China (Project No. CityU 11304115), and the National Natural Science Foundation of China (51473138).

References 1.

He, M.; Zheng, D.; Wang, M.; Lin, C.; Lin, Z., High efficiency perovskite solar cells: from

complex nanostructure to planar heterojunction. J. Mater. Chem. A 2014, 2, 5994-6003. 2.

Kim, H. S.; Lee, C. R.; Im, J. H.; Lee, K. B.; Moehl, T.; Marchioro, A.; Moon, S. J.;

Humphry-Baker, R.; Yum, J. H.; Moser, J. E.; Gratzel, M.; Park, N. G., Lead iodide perovskite sensitized all-solid-state submicron thin film mesoscopic solar cell with efficiency exceeding 9%. Sci. Rep. 2012, 2, 591. 3.

Ono, L. K.; Qi, Y., Surface and interface aspects of organometal halide perovskite materials and

solar cells. J. Phys. Chem. Lett 2016, 7, 4764-4794. 4.

Yang, W. S.; Park, B.-W.; Jung, E. H.; Jeon, N. J.; Kim, Y. C.; Lee, D. U.; Shin, S. S.; Seo, J.;

Kim, E. K.; Noh, J. H.; Seok, S. I., Iodide management in formamidinium-lead-halide–based perovskite layers for efficient solar cells. Science 2017, 356, 1376-1379.

14


Page 15 of 19 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


5. Wei, J.; Xu, R. P.; Li, Y. Q.; Li, C.; Chen, J. D.; Zhao, X. D.; Xie, Z. Z.; Lee, C. S.; Zhang, W. J.; Tang, J. X., Enhanced Light Harvesting in Perovskite Solar Cells by a Bioinspired Nanostructured Back Electrode. Adv. Energy Mater. 2017, 1700492. 6.

Yao, K.; Li, F.; He, Q.; Wang, X.; Jiang, Y.; Huang, H.; Jen, A. K.-Y., A copper-doped nickel

oxide bilayer for enhancing efficiency and stability of hysteresis-free inverted mesoporous perovskite solar cells. Nano Energy 2017, 40, 155-162. 7.

Hwang, I.; Jeong, I.; Lee, J.; Ko, M. J.; Yong, K., Enhancing stability of perovskite solar cells to

moisture by the facile hydrophobic passivation. ACS Appl. Mater. Interfaces 2015, 7, 17330-17336. 8.

Conings, B.; Drijkoningen, J.; Gauquelin, N.; Babayigit, A.; D'Haen, J.; D'Olieslaeger, L.;

Ethirajan, A.; Verbeeck, J.; Manca, J.; Mosconi, E.; Angelis, F. D.; Boyen, H.-G., Intrinsic Thermal Instability of Methylammonium Lead Trihalide Perovskite. Adv. Energy Mater. 2015, 5, 1500477. 9.

Niu, G.; Yu, H.; Li, J.; Wang, D.; Wang, L., Controlled orientation of perovskite films through

mixed cations toward high performance perovskite solar cells. Nano Energy 2016, 27, 87-94. 10.

Misra, R. K.; Aharon, S.; Li, B.; Mogilyansky, D.; Visoly-Fisher, I.; Etgar, L.; Katz, E. A.,

Temperature- and Component-Dependent Degradation of Perovskite Photovoltaic Materials under Concentrated Sunlight. J. Phys. Chem. Lett. 2015, 6, 326-330. 11.

Zhang, X.; Ren, X.; Liu, B.; Munir, R.; Zhu, X.; Yang, D.; Li, J.; Liu, Y.; Smilgies, D.-M.; Li,

R.; Yang, Z.; Niu, T.; Wang, X.; Amassian, A.; Zhao, K.; Liu, S., Stable high efficiency two-dimensional perovskite solar cells via cesium doping. Energy Environ. Sci. 2017, DOI: 10.1039/C7EE01145H. 12.

Akbulatov, A. F.; Luchkin, S. Y.; Frolova, L. A.; Dremova, N. N.; Gerasimov, K. L.; Zhidkov,

I. S.; Anokhin, D. V.; Kurmaev, E. Z.; Stevenson, K. J.; Troshin, P. A., Probing the Intrinsic Thermal and Photochemical Stability of Hybrid and Inorganic Lead Halide Perovskites. J. Phys. Chem. Lett. 2017, 8, 1211-1218. 13.

Divitini, G.; Cacovich, S.; Matteocci, F.; Cinà, L.; Di Carlo, A.; Ducati, C., In situ observation

of heat-induced degradation of perovskite solar cells. Nat. Energy 2016, 1, 15012. 14.

Hailegnaw, B.; Kirmayer, S.; Edri, E.; Hodes, G.; Cahen, D., Rain on Methylammonium Lead

Iodide Based Perovskites: Possible Environmental Effects of Perovskite Solar Cells. J. Phys. Chem. Lett. 2015, 6, 1543-1547. 15



15.

Page 16 of 19

Dualeh, A.; Tétreault, N.; Moehl, T.; Gao, P.; Nazeeruddin, M. K.; Grätzel, M., Effect of

Annealing Temperature on Film Morphology of Organic-Inorganic Hybrid Pervoskite Solid-State Solar Cells. Adv. Funct. Mater. 2014, 24, 3250-3258. 16.

Lin, Y.; Bai, Y.; Fang, Y.; Wang, Q.; Deng, Y.; Huang, J., Suppressed Ion Migration in

Low-Dimensional Perovskites. ACS Energy Lett. 2017, 2, 1571-1572. 17.

Ono, L. K.; Raga, S. R.; Wang, S.; Kato, Y.; Qi, Y., Temperature-dependent hysteresis effects

in perovskite-based solar cells. J. Mater. Chem. A 2015, 3, 9074-9080. 18.

Zhang, T.; Chen, H.; Bai, Y.; Xiao, S.; Zhu, L.; Hu, C.; Xue, Q.; Yang, S., Understanding the

relationship between ion migration and the anomalous hysteresis in high-efficiency perovskite solar cells: A fresh perspective from halide substitution. Nano Energy 2016, 26, 620-630. 19.

Tsai, H.; Nie, W.; Blancon, J. C.; Stoumpos, C. C.; Asadpour, R.; Harutyunyan, B.; Neukirch,

A. J.; Verduzco, R.; Crochet, J. J.; Tretiak, S.; Pedesseau, L.; Even, J.; Alam, M. A.; Gupta, G.; Lou, J.; Ajayan, P. M.; Bedzyk, M. J.; Kanatzidis, M. G., High-efficiency two-dimensional Ruddlesden-Popper perovskite solar cells. Nature 2016, 536, 312-316. 20.

Qing, J.; Chandran, H.-T.; Cheng, Y.-H.; Liu, X.-K.; Li, H.-W.; Tsang, S.-W.; Lo, M.-F.; Lee,

C.-S., Chlorine incorporation for enhanced performance of planar perovskite solar cell based on lead acetate precursor. ACS Appl. Mater. Interfaces 2015, 7, 23110-23116. 21.

Cao, D. H.; Stoumpos, C. C.; Farha, O. K.; Hupp, J. T.; Kanatzidis, M. G., 2D Homologous

Perovskites as Light-Absorbing Materials for Solar Cell Applications. J. Am. Chem. Soc. 2015, 137, 7843-7850. 22.

Yuan, M.; Quan, L. N.; Comin, R.; Walters, G.; Sabatini, R.; Voznyy, O.; Hoogland, S.; Zhao,

Y.; Beauregard, E. M.; Kanjanaboos, P.; Lu, Z.; Kim, D. H.; Sargent, E. H., Perovskite energy funnels for efficient light-emitting diodes. Nature Nanotech. 2016, 11, 872-877. 23.

Smith, I. C.; Hoke, E. T.; Solis-Ibarra, D.; McGehee, M. D.; Karunadasa, H. I., A layered

hybrid perovskite solar-cell absorber with enhanced moisture stability. Angew. Chem. Int. Ed. 2014, 53, 11232-11235. 24.

Nie, W.; Blancon, J. C.; Neukirch, A. J.; Appavoo, K.; Tsai, H.; Chhowalla, M.; Alam, M. A.;

Sfeir, M. Y.; Katan, C.; Even, J.; Tretiak, S.; Crochet, J. J.; Gupta, G.; Mohite, A. D.,

16


Page 17 of 19 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-activated photocurrent degradation and self-healing in perovskite solar cells. Nat. Commun. 2016, 7, 11574. 25.

Joshi, P. H.; Zhang, L.; Hossain, I. M.; Abbas, H. A.; Kottokkaran, R.; Nehra, S. P.; Dhaka,

M.; Noack, M.; Dalal, V. L., The physics of photon induced degradation of perovskite solar cells. AIP Adv. 2016, 6, 115114. 26.

Guerrero, A.; Garcia-Belmonte, G.; Mora-Sero, I.; Bisquert, J.; Kang, Y. S.; Jacobsson, T. J.;

Correa-Baena, J.-P.; Hagfeldt, A., Properties of Contact and Bulk Impedances in Hybrid Lead Halide Perovskite Solar Cells Including Inductive Loop Elements. J. Phys. Chem. C 2016, 120, 8023-8032. 27.

Ma, C.; Shen, D.; Qing, J.; Chandran, H. T.; Lo, M.-F.; Lee, C.-S., Effects of Small Polar

Molecules (MA+ and H2O) on Degradation Processes of Perovskite Solar Cells. ACS Appl. Mater. Interfaces 2017, 9, 14960-14966. 28.

Leguy, A. M. A.; Hu, Y.; Campoy-Quiles, M.; Alonso, M. I.; Weber, O. J.; Azarhoosh, P.; van

Schilfgaarde, M.; Weller, M. T.; Bein, T.; Nelson, J.; Docampo, P.; Barnes, P. R. F., Reversible Hydration of CH3NH3PbI3 in Films, Single Crystals, and Solar Cells. Chem. Mater. 2015, 27, 3397-3407. 29.

Song, Z.; Abate, A.; Watthage, S. C.; Liyanage, G. K.; Phillips, A. B.; Steiner, U.; Graetzel,

M.; Heben, M. J., Perovskite Solar Cell Stability in Humid Air: Partially Reversible Phase Transitions in the PbI2-CH3NH3I-H2O System. Adv. Energy Mater. 2016, 6, 1600846. 30.

Chen, W.; Liu, F. Z.; Feng, X. Y.; Djurišić, A. B.; Chan, W. K.; He, Z. B., Cesium Doped

NiOx as an Efficient Hole Extraction Layer for Inverted Planar Perovskite Solar Cells. Adv. Energy Mater. 2017, 1700722. 31.

Leyden, M. R.; Ono, L. K.; Raga, S. R.; Kato, Y.; Wang, S.; Qi, Y., High performance

perovskite solar cells by hybrid chemical vapor deposition. J. Mater. Chem. A 2014, 2, 18742-18745. 32. Wang, Q.; Chen, B.; Liu, Y.; Deng, Y.; Bai, Y.; Dong, Q.; Huang, J., Scaling behavior of moisture-induced grain degradation in polycrystalline hybrid perovskite thin films. Energy Environ. Sci. 2017, 10, 516-522.

17



33.

Page 18 of 19

Kim, H. S.; Seo, J. Y.; Park, N. G., Material and device stability in perovskite solar cells.

ChemSusChem 2016, 9, 2528. 34.

Troughton, J.; Hooper, K.; Watson, T. M., Humidity resistant fabrication of CH3NH3PbI3

perovskite solar cells and modules. Nano Energy 2017, 39, 60-68. 35.

Yuan, Y.; Huang, J., Ion migration in organometal trihalide perovskite and its impact on

photovoltaic efficiency and stability. Acc. Chem. Res. 2016, 49, 286-293. 36.

Kato, Y.; Ono, L. K.; Lee, M. V.; Wang, S.; Raga, S. R.; Qi, Y., Silver iodide formation in

methyl ammonium lead iodide perovskite solar cells with silver top electrodes. Adv. Mater. Interfaces 2015, 2, 1500195. 37.

Bag, M.; Renna, L. A.; Adhikari, R. Y.; Karak, S.; Liu, F.; Lahti, P. M.; Russell, T. P.;

Tuominen, M. T.; Venkataraman, D., Kinetics of ion transport in perovskite active layers and its implications for active layer stability. J. Am. Chem. Soc 2015, 137, 13130-13137. 38.

Azpiroz, J. M.; Mosconi, E.; Bisquert, J.; De Angelis, F., Defect migration in

methylammonium lead iodide and its role in perovskite solar cell operation. Energy Environ. Sci. 2015, 8, 2118-2127. 39.

Haruyama, J.; Sodeyama, K.; Han, L.; Tateyama, Y., First-principles study of ion diffusion in

perovskite solar cell sensitizers. J. Am. Chem. Soc. 2015, 137, 10048-10051. 40.

Xu, X.; Ma, C.; Cheng, Y.; Xie, Y.-M.; Yi, X.; Gautam, B.; Chen, S.; Li, H.-W.; Lee, C.-S.; So,

F., Ultraviolet-ozone surface modification for non-wetting hole transport materials based inverted planar perovskite solar cells with efficiency exceeding 18%. J. Power Sources 2017, 360, 157-165.

18


Page 19 of 19 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

19


Heat Treatment for Regenerating the Degraded Low Dimensional

Recommend Documents