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Shanghai Innovation Institute for Materials, Shanghai 200444 , China. ACS Sustainable Chem. Eng. , 2018, 6 (6), pp 7558–7564. DOI: 10.1021/acssusche...
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Cyclic Utilization of Lead in Carbon-Based Perovskite Solar Cells Sheng Zhang, Lili Shen, Mianji Huang, Yu Yu, Lei Lei, Jun Shao, Qingbao Zhao, Zihua Wu, Jinmin Wang, and Songwang Yang ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.8b00314 • Publication Date (Web): 03 May 2018 Downloaded from http://pubs.acs.org on May 3, 2018

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Cyclic Utilization of Lead in Carbon-Based Perovskite Solar Cells Sheng Zhang†,§, Lili Shen†,§, Mianji Huang§, Yu Yu§, Lei Lei§, Jun Shao§, Qingbao Zhao§, Zihua Wu†, Jinmin Wang†,‡* and Songwang Yang§* †

School of Environmental and Materials Engineering, College of Engineering, Shanghai

Polytechnic University, Shanghai 201209, China. §

CAS Key Laboratory of Materials for Energy Conversion, Shanghai Institute of Ceramics,

Chinese Academy of Sciences, 588 Heshuo Road, Shanghai 201899, China. ‡

Shanghai Innovation Institute for Materials, Shanghai 200444, China

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KEYWORDS: Lead, NH3·H2O, Cyclic utilization, Carbon-based, Perovskite solar cells

ABSTRACT: An environmentally friendly dissolving-precipitating method is developed to recycle lead from carbon-based perovskite solar cells (PSCs). N, N-Dimethylformamide (DMF) was used to dissolve PSCs and to obtain lead containing lixivium. NH3·H2O was used as a precipitator to extract lead ions from the lixivium. The result analyzed by inductively coupled plasma optical emission (ICP-OES) shows that 99.9 % of lead can be extracted by NH3·H2O. Then, HI was used to generate PbI2. ICP-OES analysis and thermodynamic calculation are used to analyze the lead content. The results show that few PbI2 transforms into [PbI4]2- due to the low concentration of hydroiodic acid (HI). The calculated lead recovery rate is 95.7 %. The recycled PbI2 was used to fabricate carbon-based PSCs achieving an efficiency of 11.36 %, which is comparable to that (12.17 %) of carbon-based PSCs fabricated with commercial PbI2. The developed process provides a new approach for the cyclic utilization of lead in carbon-based PSCs to avoid lead pollution.

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INTRODUCTION Perovskite solar cells (PSCs) have attracted considerable attention in recent years1-5. The perovskite materials (ABX3, A= Cs, CH3NH3, NH=CHNH3, B = Pb, Sn; X = Cl, Br and I) have superior properties and have been applied to solar cells, light-emitting diode (LED), photodetectors, lasers, water-splitting and other electronic applications6. Nowadays, with the improvement of the stability, PSCs would probably become the nextgeneration cheaper new energy. The efficiency plays an important role in reducing the cost and the stability is the key to the commercialization of PSCs7,8. The siliconperovskite tandem solar cells have an ultrahigh efficiency, which might be the direction of future new energy9-11. And the theoretical efficiency of such structured solar cells can reach 35 %12,13. However, the instability of perovskite materials can be a crucial factor hindering the commercialization of PSCs. Researchers are dedicated to studying twodimensional (2D), all inorganic PSCs, all inorganic charge contacts as well as discrete iron(III) oxide nanoislands for PSCs, which improved the stability of PSCs14-18. The 2D/3D carbon-based PSCs can even achieve one-year life19. These technologies contribute to the commercialization of PSCs greatly, but the toxic property of PSCs still brings some environmental concern. Some efforts such as replacing lead with non-toxic element that has been put into the research of these problems20,21. However, it seems that the toxic problem has not been addressed substantially. Replacing lead with non-toxic elements completely, such as Ge and Sn does not seem to be a good choice. And the PSCs fabricated with CH3NH3SnI3 or NH=CHNH3SnI3 show poor performance with low efficiency and poor stability22. Lead element is still indispensable element for perovskite

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material of high performance PSCs, because the ionic size of lead ions is more suitable to sustain ABX3 structure with a Goldschmidt tolerance factor23. As we know, unfortunately, lead is unnecessary element to human body. The blood lead concentration is inversely and significantly associated with intelligence quotient (IQ)24. Lead can destroy protein and has negative influence on children’ intelligence25. In fact, if human are exposed to an environment containing high-concentration lead, their nerve immune, renal and cardiovascular systems would be affected negatively26. Waste electrical and electronic equipment (WEEE) has updated its directive in August, 2012, ruling that waste photovoltaic modules should be recycled at their end of life27. PbI2 is an essential material to fabricate PSCs28, which helps to fabricate high performance of PSCs29. Carbon-based PSCs are most promising candidate to achieve commercialization, because the stability of carbon-based PSC shows superior stability compared with metal-based PSCs19,30. The carbon-based PSCs with a structure of fluorine-doped

tin

oxide

(FTO)/compact

TiO2

(c-TiO2)/mesoporous

TiO2

(m-

TiO2)/CH3NH3PbI3 film/carbon electrode can achieve the efficiency of over 14 % according to previous reports31,32.Thus, it is necessary to develop a new method to recycle carbon-based PSCs firstly. It is reported that organic-inorganic perovskite material is easily dissolved in polarity solvent, especially in N, N-Dimethylformamide (DMF)21. By this way, lead ions can be lixiviated from degraded carbon-based PSCs by immersing the cells into DMF. Lead can also be sequestrated by resin or by removing DMF under vacuum in order to obtain PbI2 in lead leaching solvent33,34 However, on the one hand, solvent extraction requires heating and vacuum, which may have potential harm to workers and pollute the environment. On

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the other hand, the structure of carbon-based PSCs is different from that of metal-based PSCs in which the former has no hole conductor layer. Thus, it is not necessary to use toxic chlorobenzene to remove the hole conductor layer. The carbon electrode is directly contacted with the perovskite film. It will not be peeled off until the perovskite film dissolving in DMF, which is different from the method of recycling metal-based PSCs with two-step process20,34. Here, we developed an environmentally friendly method to cyclically utilize lead ions from carbon-based PSCs for the first time. NH3·H2O was used as a precipitator to precipitate lead ions and HI was used to react with Pb(OH)2 to obtain PbI2 which can be re-used as raw materials for fabricating PSCs.

EXERPERIMENTAL SECTION Materials. DMF (Sinopharm Chemical Reagent Co. Ltd, 99.5 %), Commercial PbI2 (Borun New Material Technology Co. Ltd, 99.9985 %), CH3NH3I (Tokyo Chemical Industry, 98 %), discarded aged carbon-based perovskite solar cells (home-made), NH3·H2O (Sinopharm Chemical Reagent Co. Ltd, 25 ~ 28 wt%), Dimethyl sulfoxide (DMSO) (Sigma Aldrich, 99.9 %), Carbon paste (home-made), HI (Aladdin 57 wt% in water). Lead recycling process. 120 pieces of aged carbon-based PSCs were washed for three times by using 50.0, 30.0 and 20.0 mL of DMF, each for 5 min, respectively. After that, the mixture solution was centrifuged at 9800 rpm for 20 min in order to get a lixivium containing lead ions and remove carbon electrode at the same time. The carbon electrode needs to be washed for three times with 10.0 mL of DMF and centrifuged for three times and the supernatant needs to be collected as well. Then, the collected supernatant was filtered through a

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polytetrafluoroethylene (PTFE) filter (0.22 µm). Finally, 130.0 mL of lixivium containing lead ions was collected. 20.0 mL of the obtained lead lixivium mentioned above was treated with the following method: 2.0 mL of NH3·H2O solution was dropped into 20.0 mL of the obtained lixivium and stirred vigorously for 25 min. The lixivium became turbid immediately and white precipitation was formed. Then, the precipitate was separated by centrifugation. 22.0 mL of supernatant (Supernatant Ι, was obtained by centrifuging the solution that was obtained by dropping 2.0 mL of NH3·H2O into 20.0 mL of lead lixivium) was collected for ICP-OES analysis. The white precipitate was washed for four times by using deionized water. Then 20.1 mL of 0.038 M of HI solution was dropped into the obtained white precipitate. Yellow precipitate was formed. After that, the mixture solution was centrifuged at 9800 rpm for 20 min in order to get a supernatant (Supernatant Ⅱ, was obtained by centrifuging the solution that was obtained by dropping 20.1 mL of HI solution into the white precipitate). And then the yellow precipitate was centrifuged and washed with deionized water. Finally, yellow powder was obtained after drying at 80 oC overnight. Fabrication

of

carbon-based

perovskite

solar

cells.

The

perovskite

(CH3NH3PbI3) precursor was prepared with the proportion of 0.006 mol of PbI2 and 0.006 mol of CH3NH3I powder dissolving in 0.425 mL of DMSO and 3.890 mL of DMF. Fluorine-doped tin oxide (FTO, 7Ω/□) glasses were purchased from Pilkington company and were cleaned by deionized water, acetone and ethyl alcohol respectively in an ultrasonic bath for 30 min and were treated in ultraviolet ozone system (UV-O3) for 15 min to remove the organic residues subsequently. About 40 nm-thick c-TiO2 was

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prepared by spin-coating with home-made TiO2 sol. Then the film was annealed at 510 oC for 30 min. After that, the substrates were dipped in 40 mM TiCl4 solution at 70 °C for 30 min. After cooling, the substrates were washed with deionized water and ethanol, and then the substrates were dried and sintered again at 510 °C for 30 min. Then the m-TiO2 was spin-coated on the c-TiO2 layer and annealed at 510 oC for 30 min. CH3NH3PbI3 solution was then spin-coated on the m-TiO2 layer with a speed of 4000 rpm for 30 s and the substrate was annealed at 100 oC for 10 min. After that, about 24 µm-thick of carbon electrode was screen-printed on the perovskite film. CHARACTERIZATIONS Scanning electron microscopy (SEM) images of the perovskite films were obtained using field emission scanning electron microscope (FEI Magellan 400). X-ray diffraction (XRD) measurements were performed with a Bruker, D8-Advance X-ray diffractometer using Cu Kα radiation under the operation conditions of 40 kV and 40 mA from 10° to 80°, with a scanning speed of 5°/min. UV-vis spectra were recorded on a Shimadzu UV2550PC spectrometer. The current density-voltage (I-V) curves were measured under AM 1.5G illumination of 100 mW/cm2 with a Yokogawa-7563 source meter in combination with a solar simulator (YSS-150A, Yamashita Denso Corporation, Japan) equipped with a 1000 W xenon lamp. The exact light intensities of the measurements were calibrated with a silicon photo-detector (BS-520). The I-V curves were obtained by applying an external voltage bias with a scan rate of 40 mV/s. Incident photon-to-current conversion efficiency (IPCE) curves were measured with CEP1500 from 300-900 nm using a Xe source (BSOX300LC). And the signal was recorded as a function of the wavelength using a SM-250 system (Bunkoh-keiki, Japan) and calibrated using a standard Si photodiode (S13370-

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1010BQ). Steady photoluminescence (PL) spectroscopy was recorded on a Horiba Jobinyvon (Horiba-Ltd) Nanolog device with an excitation wavelength of 466 nm. The purity of recycled PbI2 and the lead content in lixivium and supernatant were measured by ICP-OES (Agilent Technologies 5100).

RESULTS AND DISSCUSSION The dissolution-precipitation method for cyclic utilization of lead from aged carbonbased PSCs is illustrated in Figure 1. DMF was used to dissolve the perovskite material in aged carbon-based PSCs (CH3NH3PbI3). The structure of the carbon-based PSCs that we recycled is FTO/c-TiO2/m-TiO2/CH3NH3PbI3 film/carbon electrode. As far as the structure is concerned, the independent degraded perovskite (CH3NH3PbI3) film can separate carbon electrode and substrate of FTO/c-TiO2/m-TiO2. Organic-inorganic perovskite can be easily dissolved in polar solvent, especially in DMF7. According to the experimental section, the perovskite films degraded partly or entirely are easily dissolved in DMF. When the aged carbon-based PSCs were immersed into DMF, the degraded perovskite film was dissolved into DMF immediately and the carbon electrode peeled off from the substrate simultaneously. After centrifugation, insoluble material such as carbon electrode was removed. And the insoluble material was washed by DMF subsequently and centrifuged for three times in order to make sure that the perovskite material was dissolved into DMF thoroughly. PTFE filter (0.22 µm) was used to filter supernatant solution to obtain clean lixivium containing lead ions. After filtration, the liquid supernatant containing lead ions was collected.

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XRD was used to characterize the discarded cells washed by DMF and substrate with fresh m-TiO2 (Figure 2a). It is obvious to find that the diffraction peaks of TiO2 substrate washed by DMF are in good agreement with the fresh one, which means the majority of perovskite material can be washed by DMF thoroughly. We also characterized the transmittance of the substrates. The transmittance of aged carbon-based PSCs washed by DMF is quite the same as that of the fresh one (FTO/c-TiO2/m-TiO2), which means that little undissolved residual material exists in the m-TiO2 electrode (Figure 2b). The substrate with m-TiO2 can be recycled for fabricating new carbon-based PSCs. When the device gets degraded, it can be washed with DMF in order to remove the degradable part. Then the fresh perovskite film can be prepared on the m-TiO2. The I-V curves of original device, degraded one, and device fabricated with the old substrate are shown in Figure 3, respectively. The corresponding parameters are listed in Table 1. The efficiency of carbon-based PSC only decreases by 1.5 %, which means that the old substrates can function well. According to our experiment, the carbon-based PSCs degraded following with the efficiency of the cell dropping by a half of its original efficiency. And the perovskite films degraded seriously. We define them as aged carbon-based solar cells. The color of perovskite films would change from dark to yellow, which means that CH3NH3PbI3 would gradually collapse and transfer into PbI2 under the condition of moisture, high temperature or light35,36. Actually, the degradation degree of carbon-based PSCs has no influence on lead recycling. Because both of CH3NH3PbI3 and PbI2 can be dissolved in DMF and precipitated by NH3·H2O. The reported recycling method can be applied to carbon-based

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PSCs degradation entirely and cells degrade partly in which CH3NH3PbI3 partly transformed into the PbI2 entirely and partly. 2.0 mL of NH3·H2O (25~28 wt%) was used as the reactant to precipitate lead ions to form Pb(OH)2 precipitate. When NH3·H2O was dropped into 20.0 mL of lixivium containing lead ions and stirred, the lixivium became turbid and white precipitate was formed (Equation 1). Here, an excessive amount of NH3·H2O need to be dipped in the lixivium to make sure a complete reaction. The lead content in the lixivium is 220.0 µg/g according to ICP-OES analysis. By comparison, the lead content in 22.0 mL of supernatant Ⅱ is 0.2 µg/g, which means that 99.9 % of lead ions were precipitated by dropping NH3·H2O into the lixivium (Table 2). The white precipitate needs to be washed with deionized water for three times to remove soluble ions. NaOH and H2S are also considered as precipitators to react with Pb2+ ions from the lixivium containing lead. However, Pb(OH)2 can be dissolved in strong base to form [Pb(OH)4]2- ions. They will be dissolved into water and form clean solution when the precipitate was washed with deionized water. Thus, we think that NH3·H2O is better than NaOH for precipitating lead ions. H2S may also be another choice for the quite low Ksp of PbS37. Considering the toxicity of H2S, it is also not suitable for the precipitation process. In addition, the precipitate of PbS is too stable to form PbI2 by reacting with HI. In order to form PbI2, appropriate concentration (0.038M) of HI solution was used to react with the white precipitate to form PbI2 (Equation 2). The main reactions are listed as following: Pb2+ + 2 NH3·H2O  Pb(OH)2↓+ 2 NH4+

(1)

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Pb(OH)2 + 2 HI  PbI2 + 2 H2O

(2)

The colors of reactants change from white to yellow, which implies that Equation 2 would happen. To give a theoretical explanation, the Gibbs free energy of the reaction  (∆r ) is calculated with Equation 3. The standard Gibbs free energy of the formation

values of chemicals in Equation 2 are listed in Table 337.      ∆  = [∆  (PbI ) + 2∆  (H O)] − [∆  (Pb(OH) ) + 2∆  (HI)]

(3)

 The calculated ∆r = -436.58 kJ/mol < 0, which means that Equation 2 would move in

the forward direction. In order to calculate the lost lead in the process of dropping HI solution into Pb(OH)2 to form PbI2, ICP-OES was also used to analyze the collected supernatant. The measured lead content in 20.1 mL of supernatant Ⅱ is 8.9 µg/g. Considering the transformation of PbI2 to [PbI4]2- ions due to an excess HI solution used to form PbI2 precipitate, the calculated concentration of [PbI4]2- ions is 1.35 × 10-7 M. And considering the lead loss after dropping NH3·H2O to form Pb(OH)2, the calculated lead recovery rate is 95.7 %. The adsorption methods with poly (acrylic acid) organo-montmorillonite nanocomposites, magnetic nanocarbon adsorbents as well as nanocarbon adsorbents, graphene had been used to reduce heavy metal such as lead and hexavalent chromium in waste water26,38,39. Some reports have discussed the methods of recycling aged metal-based PSCs, ion exchange with hydroxyapatite effectively reduced the lead content in residual-lead-containing solution20,40. The methods mentioned above can also be applied to recycle lead in supernatant Ⅱ. The yellow precipitate was characterized by XRD. The result shows that the yellow precipitate is PbI2 (Figure 4). The recycled PbI2 and the commercial PbI2 were both dissolved in DMF to form solutions with the same concentration of 1.25 M. And the

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prepared solutions were spin-coated on FTO glasses and then the substrate was heated at 80 oC for 30 min to form PbI2 film. The XRD peaks of recycled PbI2 film are in good agreement with those of the commercial one. The intensities of their peaks are quite different, which should be attributed to their different crystallinity. The results confirm that the yellow precipitate is PbI2. The purity of PbI2 was analyzed by ICP-OES. According to the calculation, its purity is 99.9 % (Table 4) which is quite lower than that of the commercial PbI2 (Experiment section). To avoid environmental pollution and achieve a cyclic utilization of lead, the recycled PbI2 was used to fabricate a carbon-based PSC. For comparison, commercial PbI2 was also used to prepare a carbon-based PSC. Figure 5 shows the SEM images of the surfaces of perovskite films on m-TiO2. Both of the two films show rough and porous surfaces, and no obvious difference can be observed. The UV-vis spectra of two perovskite films deposited on m-TiO2 is shown in Figure 6a. It can be seen that the absorptance of the perovskite film fabricated with recycled PbI2 is only slightly lower than that of the perovskite film fabricated with commercial PbI2. The PL spectrum of the porous perovskite films are shown in Figure 6b. The emission peak can be observed at 760 nm under the condition of excitation wavelength of 466 nm. The quenching intensity of perovskite film fabricated with commercial PbI2 is stronger, which means that more efficient charge transfer is achieved in this film41. This result can help to achieve a better performance of carbon-based PSCs. The I-V curves of two carbon-based perovskite solar cells fabricated with recycled PbI2 and with commercial one is shown in Figure 7a. And the corresponding parameters of the two carbon-based PSCs are listed in Table 5. The device fabricated by recycled PbI2 shows an open-circuit voltage (Voc) of 0.87 V, a short-

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circuit current (Jsc) of 20.54 mA/cm2, a fill factor (FF) of 63.61 % and a power conversion efficiency (PCE) of 11.36 %. Compared with the parameters (Voc = 0.92 V, Jsc = 20.89 mA/cm2, FF = 63.64 % and PCE = 12.17 %) of the device fabricated by commercial PbI2, the device fabricated by recycled PbI2 shows comparable properties. The corresponding IPCE action curves of the two devices are shown in Figure 7b. The IPCE of the device fabricated with the recycled PbI2 is lower than that of the device fabricated with the commercial one, which results in a lower integrated current (19.36 mA/cm2) of the device fabricated with the recycled PbI2. However, this value achieves to 93.71 % of that (20.66 mA/cm2) of the device fabricated with the commercial PbI2, showing an effective cyclic utilization of lead in carbon-based PSCs.

CONCLUSIONS In conclusion, we developed a dissolution-precipitation method for the cyclic utilization of lead from carbon-based PSCs. The result shows that 99.9 % of lead ion can be extracted by NH3·H2O solution. The PbI2 was obtained by using an appropriate concentration of HI. The calculated lead recovery rate is 95.7 %. The recycled PbI2 was used to fabricate a carbon-based PSC with an efficiency of 11.36 %, which is comparable to that (12.17 %) of carbon-based PSC fabricated with commercial PbI2. The developed process provides a new approach to the cyclic utilization of lead in carbon-based PSCs to avoid lead pollution in soil and water.

AUTHOR INFORMATION E-mail address: [email protected];

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E-mail address: [email protected]

NOTES The authors declare no competing financial interest.

ACKNOWLEDGEMENTS This work was financially supported by National Natural Science Foundation of China (NSFC) (No. 61775131, No. 51590902, No. 61376009), Shanghai Municipal Natural Science Foundation (Grant No. 16ZR1441000), Program for Professor of Special Appointment (Eastern Scholar) at Shanghai Institutions of Higher Learning (No. 2013-70), “Shu Guang” project supported by Shanghai Municipal Education Commission and Shanghai Education Development Foundation (No. 13SG55), Shanghai Polytechnic University Graduate Student Foundation (No. EGD16YJ006).

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(3) Jeon, N. J.; Noh, J. H.; Kim, Y. C.; Yang, W. S.; Ryu, S.; Seok, S. I. Solvent engineering for high-performance inorganic-organic hybrid perovskite solar cells. Nat Mater, 2014, 13, 897-903. DOI 10.1038/nmat4014. (4) Arora, N.; Dar, M. I.; Hinderhofer, A.; Pellet, N.; Schreiber, F.; Zakeeruddin, S. M.; Gratzel, M. Perovskite solar cells with CuSCN hole extraction layers yield stabilized efficiencies greater than 20 %. Science, 2017, 358, 739-744. DOI 10.1126/science.aam5655. (5) Correa-Baena, J. P.; Saliba, M.; Buonassisi, T.; Gratzel, M.; Abate, A.; Tress, W.; Hagfeldt, A. Promises and challenges of perovskite solar cells. Science, 2017, 358, 739-744. DOI 10.1126/science.aam6323. (6) Zhao, Y. X.; Zhu, K. Organic-inorganic hybrid lead halide perovskites for optoelectronic and electronic applications. Chem. Soc. Rev., 2016, 45, 655-689. DOI 10.1039/c4cs00458b. (7) Xu, T. T.; Chen, L. X.; Guo, Z. H.; Ma, T. L. Strategic improvement of the long-term stability of perovskite materials and perovskite solar cells. Phys. Chem. Chem. Phys., 2016, 18, 27026-27050. DOI 10.1039/c6cp04553g. (8) Liu, T.; Yu, L. P.; Liu, H.; Hou, Q. Z.; Wang, C.; He, H. C.; Li, J. B.; Wang, N.; Wang, J. S.; Guo, Z. H. Ni Nanobelts induced enhancement of hole transport and collection for high efficiency and ambient stable mesoscopic perovskite solar cells. J. Mater. Chem. A, 2017, 5, 4292-4299. DOI 10.1039/c6ta10470c. (9) Loper, P.; Niesen, B.; Moon, S. J.; de Nicolas, S. M.; Holovsky; Remes, Z.; Ledinsky, M.; Haug, F. J.; Yum, J. H.; De Wolf, S.; Ballif, C. Organic-inorganic halide perovskites: perspectives for silicon-based tandem solar cells. IEEE. J. Photovolt, 2014, 4, 1545-1551. DOI 10.1109/j.photov.2014.2355421.

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(15) Liang, J.; Wang, C. X.; Wang, Y. R.; Xu, Z. R.; Lu, Z. P.; Ma, Y.; Zhu, H. F.; Hu, Y.; Xiao, C. C.; Yi, X.; Zhu, G. Y.; Lv, H. L.; Ma, L. B.; Chen, T.; Tie, Z. X.; Jin, Z.; Liu, J. All-inorganic perovskite solar cells. J. Am. Chem. Soc., 2016, 138, 15829-15832. DOI 10.1021/jacs.6b10227. (16) Chang, X. W.; Li, W. P.; Zhu, L. Q.; Liu, H. C.; Geng, H. F.; Xiang, S. S.; Liu, J.; Chen, H. N. Carbon-based CsPbBr3 perovskite solar cells: all-ambient processes and high thermal stability. ACS. Appl. Mater. Inter., 2016, 8, 33649-33655. DOI 10.1021/acsami.6b11393. (17) Luo, Q.; Ma, H.; Hao, F.; Hou, Q. Z.; Ren, J.; Wu, L. L.; Yao, Z. B.; Zhou, Y.; Wang, N.; Jiang, K. L.; Lin, H.; Guo, Z. H. Carbon nanotube based inverted flexible perovskite solar cells with all-inorganic charge contacts. Adv. Funct. Mater, 2017, 27, 1703068. DOI 10.1002/adfm.201703068. (18) Luo, Q.; Chen, H. J.; Lin, Y. Z.; Du, H. Y.; Hou, Q. Z.; Hao, F.; Wang, N.; Guo, Z. H.; Huang, J. S. Discrete iron(III) oxide nanoislands for efficient and photostable perovskite solar cells. Adv. Funct. Mater., 2017, 27, 1702090. DOI 10.1002/adfm.201702090. (19) Grancini, G.; Roldan-Carmona, C.; Zimmermann, I.; Mosconi, E.; Lee, X.; Martineau, D.; Narbey, S.; Oswald, F.; De Angelis, F.; Grätzel, M.; Nazeeruddin, M. K. One-year stable perovskite solar cells by 2D/3D interface engineering. Nat. Commun., 2017, 8, 15684. DOI 10.1038/ncomms15684. (20) Kim, B. J.; Kim, D. H.; Kwon, S. L.; Park, S. Y.; Li, Z.; Zhu, K.; Jung, H. S. Selective dissolution of halide perovskites as a step towards recycling solar cells. Nat. Commun., 2016, 7, 11735. DOI 10.1038/ncomms11735. (21) Huang, L. K.; Xu, J.; Sun, X. X.; Xu, R.; Du, Y. Y.; Ni, J.; Cai, H. K.; Li, J.; Hu, Z. Y.; Zhang, J. J. New films on old substrates: toward green and sustainable energy production via

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recycling of functional components from degraded perovskite solar cells. ACS. Sustain. Chem. Eng., 2017, 5, 3261-3269. DOI 10.1021/acssuschemeng.6b03089. (22) Yang, S. D.; Fu, W. F.; Zhang, Z. Q.; Chen, H. Z.; Li, C. Z. Recent advances in perovskite solar cells: efficiency, stability and lead-free perovskite. J. Mater. Chem. A., 2017, 5, 1146211482. DOI 10.1039/c7ta00366h. (23) Kieslich, G.; Sun, S. J.; Cheetham, A. K. Solid-state principles applied to organic–inorganic perovskites: new tricks for an old dog. Chem. Sci., 2014, 5, 4712-4715. DOI 10.1039/c4sc02211d. (24) Chiodo, L. M.; Covington, C.; Sokol, R. J.; Hannigan, J. H.; Jannise, J.; Ager, J.; Greenwald, M.; Delaney-Black, V. Blood lead levels and specific attention effects in young children. Neurotoxicol. Teratol., 2007, 29, 538-546. DOI 10.1016/j.ntt.2007.04.001. (25) Canfield, R. L.; Henderson, C. R., Jr.; Cory-Slechta, D. A.; Cox, C.; Jusko, T. A.; Lanphear, B. P. Intellectual impairment in children with blood lead concentrations below 10 µg per deciliter. N. Engl. J. Med, 2003, 348, DOI 1517-1526.10.1056/nejmoa022848. (26) Ma, Y. L.; Lv, L.; Guo, Y. R.; Fu, Y. J.; Shao, Q.; Wu, T. T.; Guo, S. J.; Sun, K.; Guo, X. K.; Wujcik, E. K.; Guo, Z. H. Porous lignin hased poly (acrylic acid)/organo-montmorillonite nanocomposites: swelling behaviors and rapid removal of Pb (II) ions. Polymer, 2017, 128, 1223. DOI 10.1016/j.polymer.2017.09.009. (27) Latunussa, C. E. L.; Ardente, F.; Blengini, G. A.; Mancini, L. Life cycle assessment of an innovative recycling process for crystalline silicon photovoltaic panels. Sol. Energy Mater. Sol. Cells., 2016, 156, 101-111. DOI 10.1016/j.solmat.2016.03.020. (28) 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

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sensitized all-solid-state submicron thin film mesoscopic solar cell with efficiency exceeding 9%. Sci. Rep., 2012, 2, 591. DOI 10.1038/srep00591. (29) Ahn, N.; Son, D. Y.; Jang, I. H.; Kang, S. M.; Choi, M.; Park, N. G. Highly reproducible perovskite solar cells with average efficiency of 18.3% and best efficiency of 19.7% fabricated via lewis base adduct of lead(II) iodide. J. Am. Chem. Soc., 2015, 137, 8696-8699. DOI 10.1021/jacs.5b04930. (30) Luo, Q.; Ma, H.; Hou, Q. Z.; Li, Y. X.; Ren, J.; Dai, X. Z.; Yao, Z. B.; Zhou, Y.; Xiang, L. C.; Du, H. Y.; He, H. C.; Wang, N.; Jiang, K. L.; Lin, H.; Zhang, H. W.; Guo, Z. H. All-carbonelectrode-based endurable flexible perovskite solar cells. Adv. Funct. Mater., 2018, 28, 1706777. DOI 10.1002/adfm.201706777. (31) Chen, H. N.; Wei, Z. H.; He, H. X.; Zheng, X. L.; Wong, K. S.; Yang, S. H. Solvent engineering boosts the efficiency of paintable carbon-based perovskite solar cells beyond 14 %. Adv. Energy. Mater., 2016, 6, 1502087. DOI 10.1002/aenm.201502087. (32) Chen, H. N.; Yang, S. H. Carbon-based perovskite solar cells without hole transport materials:

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(35) Merdasa, A.; Bag, M.; Tian, Y.; Källman, E.; Dobrovolsky, A.; Scheblykin, I. G. SuperResolution luminescence microspectroscopy reveals the mechanism of photoinduced degradation in CH3NH3PbI3 perovskite nanocrystals. J. Phys. Chem. C, 2016, 120, 10711-10719. DOI 10.1021/acs.jpcc.6b03512. (36) Berhe, T. A.; Su, W.-N.; Chen, C.-H.; Pan, C.-J.; Cheng, J.-H.; Chen, H.-M.; Tsai, M.-C.; Chen, L.-Y.; Dubale, A. A.; Hwang, B.-J. Organometal halide perovskite solar cells: degradation and stability. Energ. Environ. Sci., 2016, 9, 323-356. DOI 10.1039/c5ee02733k. (37) Lange, N. A.; Speight, J. G. Lange’s handbook of chemistry, 16th ed.; McGraw-Hill: New York. 2004. (38) Yu, G. Q.; Lu, Y.; Guo, J.; Patel, M. S.; Bafana, A.; Wang, X. F.; Qiu, B.; Jeffryes, C.; Wei, S. Y.; Guo, Z. H.; Wujcik, E. K. Carbon nanotubes, graphene, and their derivatives for heavy metal removal. Adv. Compos. Hybrid. Mater., 2017, 1, 56-78. DOI 10.1007/s42114-017-0004-3. (39) Huang, J.; Cao, Y.; Shao, Q.; Peng, X.; Guo, Z. Magnetic nanocarbon adsorbents with enhanced hexavalent chromium removal: morphology dependence of fibrillar vs particulate structures. Ind. Eng. Chem. Res., 2017, 56, 10689-10701. DOI 10.1021/acs.iecr.7b02835. (40) Shah, D. B.; Phadke, A. V.; Kocher, W. M. Lead removal from foundry waste by solvent extraction.

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Tables

Table 1. The I-V parameter of carbon-based PSCs (original one), its degraded one and the carbon-based PSCs fabricated with the substrate of degraded one. Carbon-based PSCs

Voc (V)

Jsc (mA·cm-2)

FF (%)

Max. Eff (%)

Original one

0.934

20.04

65.25

12.21

Degraded one

0.709

18.17

51.26

6.61

Old substrate

0.912

20.88

63.19

12.03

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Table 2. The lead contents in lixivium and supernatant analyzed by ICP-OES. Component

Lead content (µg/g)

Lead contained lixivium

220.0

Supernatant Ⅰ (collected after reaction with NH3·H2O)

0.2

Supernatant Ⅱ (collected after reaction with HI)

8.9

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Table 3 The Gibbs free energy of formation values of chemicals in Equation 2. Chemicals

 ∆f  (kJ/mol)

Pb(OH)2

-108.1

HI

PbI2

H 2O

-51.59

-173.58

-237.14

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Table 4. The impurity contents of PbI2 analyzed by ICP-OES. Component

Content (µg/g)

B

< 4.0

Ca

< 40.0

Cu

< 10.0

Mg

1.8

P

< 20.0

S

840

Ti

6.8

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Table 5. I-V parameters of carbon-based PSCs fabricated with commercial PbI2 and recycled PbI2. Voc (V)

Jsc (mA·cm-2)

FF (%)

Max. Eff (%)

Ave±std. Eff (%)

Commercial PbI2

0.92

20.89

63.64

12.17

12.02±0.12

Recycled PbI2

0.87

20.54

63.61

11.36

10.48±1.28

Carbon-based PSCs

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Figure captions

Figure 1. Illustrated cyclic utilization process of lead from carbon-based PSCs. Figure 2. (a) XRD patterns of fresh m-TiO2 substrate and degraded carbon-based PSCs washed by DMF, (b) transmittance spectra of FTO glass; FTO/c-TiO2/m-TiO2 substrate and degraded carbon-based PSCs washed by DMF. Figure 3. I-V curves of original carbon-based PSC, degraded one and the carbon-based PSC fabricated with the substrate of degraded one. Figure 4. XRD patterns of the recycled PbI2 film and commercial PbI2 film. Figure 5. SEM images of CH3NH3PbI3 films fabricated with (a) commercial PbI2 and (b) recycled PbI2. Figure 6. (a) UV-Vis spectra and (b) PL spectra of CH3NH3PbI3 films fabricated with commercial PbI2 and recycled PbI2. Figure 7. (a) I-V curves of carbon-based PSCs fabricated with recycled PbI2 and commercial PbI2, (b) corresponding IPCE curves and integrated current of carbon-based PSCs.

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Figures

Figure 1

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Figure 2

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Figure 3

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Figure 4

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Figure 5

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Figure 6

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Figure 7

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TOC Cyclic utilization of lead from carbon-based perovskite solar cells with dissolving-precipitating method achieves environmental protection and resource utilization.

For Table of Contents Use Only

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