Synthesis of (CuInS2)0.5(ZnS)0.5 Alloy Nanocrystals and Their Use

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Synthesis of (CuInS2)0.5(ZnS)0.5 Alloy Nanocrystals and their use for the Fabrication of Solar Cells via Selenization Brian Kemp Graeser, Charles J. Hages, Wei-Chang Yang, Nathaniel J. Carter, Caleb K. Miskin, Eric A. Stach, and Rakesh Agrawal Chem. Mater., Just Accepted Manuscript • DOI: 10.1021/cm501017z • Publication Date (Web): 23 Jun 2014 Downloaded from http://pubs.acs.org on June 29, 2014

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Chemistry of Materials

Synthesis of (CuInS2)0.5(ZnS)0.5 Alloy Nanocrystals and their use for the Fabrication of Solar Cells via Selenization Brian K. Graeser,† Charles J. Hages,† Wei Chang Yang,‡ Nathaniel J. Carter,† Caleb K. Miskin,† Eric A. Stach,§ and Rakesh Agrawal†* †School of Chemical Engineering, Purdue University, West Lafayette, IN 47907, USA ‡ School of Materials Engineering, Purdue University, West Lafayette, IN 47907,USA § Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, NY 11973, USA KEYWORDS: CZIS, CZISSe, CISSe, nanocrystal, photovoltaic, thin-film

ABSTRACT: As solar cell absorber materials, alloys of CuIn(S,Se)2 and Zn(S,Se) provide an opportunity to reduce the usage of indium along with the ability to tune the band gap. Here we report successful synthesis of alloyed (CuInS2)0.5(ZnS)0.5 nanocrystals by a method that solely uses oleylamine as the liquid medium for synthesis. The reactive sintering of a thin film of these nanocrystals via selenization at 500 °C results in a uniform composition alloy (CuIn(S,Se)2)0.5(Zn(S,Se))0.5 layer with micron size grains. Due to the large amount of zinc in the film, the sintered grains exhibit the zinc blende (sphalerite) structure instead of the usual chalcopyrite structure of CuIn(S,Se)2 films. The use of the selenide films as a p-type absorber layer has yielded solar cells with total area power conversion efficiencies as high as 6.7% (7.4% based on active area). These preliminary results are encouraging and indicate that with further optimization this class of materials has promise as the absorber layer in solar cells.

Chalcogenide materials have received significant attention as absorbers for thin film photovoltaic devices. Notably, materials such as CuInxGa1-xSe2 (CIGSe)1–6 and CdTe7 have been successfully used for this purpose and currently provide the most efficient thin-film solar cells.8 However, recent efforts have focused on reducing the use of costly elements, such as indium and tellurium, in favor of more earth-abundant, lowcost alternatives. To this end, the Cu2ZnSn(SzSe1-z)4 (CZTSSe) material system9–14 has received increased attention for its potential role as a viable earth-abundant alternative to CIGSe and CdTe absorbers, though to-date this technology has been unable to reach the performance level of the best performing CIGSe and CdTe devices. An alternative technology that can be employed for reducing the use of indium in photovoltaic absorbers is the (CuInSe2)y(ZnSe)1-y (CZISe) material system, where ternary chalcopyrite CuInSe2 is alloyed with binary cubic zinc blende ZnSe. This alloying has the potential to decrease the net use of indium in the absorber layer. In this alloy material system, the optical band gap of the absorber can be adjusted from 1.05 eV15 to 3.7 eV16 by controlling the degree of alloying between CuInSe2 and ZnSe, as well as through partial or complete substitution of selenium with sulfur. Additionally, the structure of the CZISe alloy can be shifted from tetragonal chalcopyrite to cubic zinc blende by increasing the ratio of ZnSe to CuInSe2 in the final film.17 The simpler crystal structure could make the device processing for this material to be more robust. ZnSe is an n-type semiconductor, while CuInSe2 is a p-type semiconductor; thus, control of ZnSe and CuInSe2 alloying can potentially lead to control of the defect characteristics of the absorber layer. These attributes could allow for this material system to reach the performance of the best CZTSSe and CIGSSe

devices. This material system has previously been utilized for a variety of semiconductor applications such as thin-film,18,19 and dye-sensitized solar cells20, quantum dot light emitting diodes,21,22 and photocatalysis.23 Similar CuIn(SzSe2-z)/ZnS core/shell nanoparticles have also been developed for use in other applications.24 In a previous attempt,18 CZISe solar cells were prepared by physical vapor deposition of zinc, selenium, copper, and indium on a substrate at 5x10-6 Torr vacuum, followed by selenization at 520°C. The authors report a power conversion efficiency (pce) of 7.2% under AM0 (1353 W/m2 irradiation) for Cu0.88In0.89Zn0.23Se2 solar cell. This composition of the chalcopyrite absorber layer can be roughly approximated as (CuInSe2)0.795(ZnSe)0.205 and is indium rich. Exploring alloy compositions which have much lower amounts of CuInSe2 is of great interest for solar cell performance. In this contribution, we present a solution method for CZISe based solar cells with an absorber layer containing an approximate composition of nearly equal amounts of all three cations. First, nanocrystals of (CuInS2)0.5(ZnS)0.5 (CZIS) are synthesized to provide an ink containing these particles. A thin film is then prepared using doctor blading onto a molybdenum coated soda lime glass. This is followed by selenization of the film at 500°C to result in a (CuIn(S,Se)2)0.5(Zn(S,Se))0.5 CZISSe film containing micron sized grains. The solar cell device is finally completed and characterized. Here we report successful synthesis of the absorber layer and solar cells with the best performing device pce of 6.7% based on total cell area of 0.47 cm2 (7.4% based on active cell area) under AM1.5 illumination. For the synthesis of Cu2ZnSnS4 nanocrystals, Miskin et al. have reported a hot-injection method where a sulfur-

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oleylamine solution is injected into a preheated flask of oleylamine, followed by the injection of an oleylamine solution of the the cation salts. The reaction is then run for a specified time before being removed from the heating source.11 This synthesis method was adopted for our synthesis of CZIS nanocrystals.25

Figure 1 (a) STEM-HAADF image of the CZIS nanocrystals, (b) PXRD pattern of the CZIS nanocrystals with CuInS (JCPDS: 27159) and ZnS (JCPDS: 5-566) standards shown for reference (c) STEM-EDS map of nanocrystals (d) Size distribution of the nanocrystals.

To confirm the formation of the desired CZIS alloy nanocrystals, energy-dispersive x-ray spectroscopy (EDS) using both scanning electron microscope (SEM), and scanning transmission electron microscopy (STEM) were employed to determine the composition and compositional uniformity; the crystallographic structure was characterized using powder xray diffraction (PXRD) patterns and high-resolution transmission electron microscopy (HRTEM). The SEM-EDS analysis gave an average bulk atomic composition of the CZIS nanocrystals to be Cu = 0.29, Zn = 0.37, In = 0.33, and S = 1.13, suggesting an atomic alloy ratio of nearly 1/1 for [CuInS2]/[ZnS]. The high-angle annular dark-field image (HAADF) and STEM-EDS maps in Figure 1(a) and (c), show that the nanocrystals contain all of the desired cations. To verify the alloying of CuInS2 with ZnS, the PXRD pattern is presented in Figure 1(b). Analysis of the PXRD pattern indicates a cubic-like crystal structure for the synthesized nanocrystals.26 The measured peak locations for the 111, 220, and 311 planes are located between those of CuInS2 and ZnS, as expected for the alloy material according to Vegard’s law.27 The interplanar spacings calculated from the XRD have been confirmed using the fast Fourier transform (FFT) diffractogram from the HRTEM image (see S.I.). No attempt to do a size separation was made and the resulting size distribution of the nanocrystals shown in Figure 1(d) is a skewed distribution with an average size of 7.0 nm and a standard deviation of 2.2 nm. The CZIS nanocrystals were doctor bladed onto a molybednum-coated soda-lime glass substrate and treated in a Se atmosphere at 500°C for 20 minutes (i.e. “selenized”) using the procedure described elsewhere.28 This process results in the reactive sintering of the nanocrystals into a dense absorber layer with micron sized grains. Evidence of grain growth/sintering can be identified through a typical XRD pattern of the selenized films (Figure 2). The full-width half-max

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of the diffraction peaks is found to significantly decrease relative to the CZIS nanocrystals in Figure 1(b). Additionally, grain growth/sintering is evident in the SEM cross-sectional image provided as Figure 3(a). Also in the image, a bi-layer structure - commonly reported for selenized nanocrystal films - is identified, and discussed below. During the selenization process, a sintered CZISSe absorber is formed as most of the sulfur in the CZIS nanocrystal lattice is replaced with selenium.

Figure 2 (a) XRD pattern of the CZISSe films and (b) a close up of the scan in the vicinity of 53° and its single peak fit corresponding to the 311 plane. CISe (JCPDS: 40-1487) and ZnSe (JCPDS: 37-1463) standards are shown for reference.

The XRD pattern in Figure 2 shows the same basic tetrahedral peaks for the CZISSe absorber as the CZIS nanocrystals. However, the diffraction peaks are shifted to slightly lower 2Θ angles due to lattice expansion from the substitution of sulfur anions with the larger selenium anions. Similar to the observation for the CZIS alloy nanocrystals, the diffraction peaks for the selenized CZISSe film fall between those of chalcopyrite CuInSe2 and zinc blende ZnSe, suggesting the desired alloy of these respective materials is maintained from the nanocrystals to the selenized films. While the diffraction peaks for the CZIS nanocrystals appear approximately halfway between CuInS2 and ZnS, the diffraction peaks for the selenized CZISSe film are shifted to a slightly higher 2Θ than the midpoint between CuInSe2 and ZnSe due to residual sulfur (≲10%, measured by EDS) left in the crystal lattice following selenization. To differentiate between the chalcopyrite and zinc blende crystal structures, a close examination of the XRD signal near a 2Θ of 53° in Figure 2(b), shows that the observed peak is indeed a single peak. This observation indicates that the film has the desired zinc blende structure, as the chalcopyrite structure should have two peaks at this location18. To verify that the desired cation ratios are maintained following the selenization process, SEM-EDS analyses of the CZIS nanocrystals and a CZISSe selenized film were compared, showing little or no significant change in cation ratios following selenization (Table 1). Table 1 Bulk SEM-EDS data for the CZIS nanocrystals and the CZISSe films Fraction of total cations Cation

Before Se treatment

After Se treatment

Copper

0.29 (±.01)

0.27 (±.02)

Zinc

0.37 (±.01)

0.35 (±.02)

Indium

0.33 (±.01)

0.38 (±.02)

To further identify the degree of alloying of CuIn(S,Se)2 and Zn(S,Se) in the selenized film, as well as investigate the bi-


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layer structure of the absorber, cross-sectional SEM-EDS mapping was performed and is presented in Figure 3(b). In the SEM-EDS maps of the film cross-section the cations are evenly dispersed throughout the CZISSe layer. This supports the conclusion from XRD that the film constitutes alloyed CZISSe

0.47 cm2. The best devices made from our synthesis achieve a total area pce of 6.7%, or 7.4% based on active area when

Figure 5 J-V characterization for devices made. Insert: table of parameters for the best performing device and EQE data for the device made from our synthesis.

Figure 3 (a) SEM cross sectional image of a selenized film (b) cross sectional EDX mapping of the elements: copper, zinc, indium, selenium, and carbon.

Figure 4 Vertical SEM-EDS linescan of a selenized film.

rather than segregated phases of any ternary or binary consituents. The absence of relative composition variations for copper, zinc, and indium observed in the vertical linescan through the width of the sintered layer (see Figure 4) further supports the conclusion that this layer is compositionally uniform. The ‘fine-grain’ layer is primarily composed of carbon and selenium with significantly reduced copper, indium, and zinc cations. This observation suggests that the fine grain layer is primarily a byproduct of the selenization process and the organic media present in the nanocrystal film rather than the residual unsintered nanocrystals. This “fine grain layer” has been observed in similarly processed CIGSSe1 and CZTSSe10 solar cells and does not prohibit device functionality in those devices either. The presence of the fine-grain layer in these devices is manifested as a series resistance, which lowers the calculated fill factor. The selenized CZISSe films were fabricated into photovoltaic devices following the standard device architecture11 of Mo (800 nm) / CZISSe (700-1000 nm) / CdS (50 nm) / i-ZnO (80 nm) / ITO (220 nm) / Ni-Al Grids with a total device area of

accounting for the shadowing due to the Ni-Al grids on the top surface. The average total area pce for the entire sample set of six cells was 6.3%. The J-V curves for the best performing cell are shown in Figure 5. External quantum efficiency (EQE) measurements demonstrate that the collection for the device is below 80% for all wavelengths (Figure 5 (inset)). This suggests that the absorption of incident light could be a primary limitation of Jsc in the cell and that a thicker sintered layer is needed. If we focus on the data just in the 550-800 nm range, the high slope is indicative of relatively poor carrier collection throughout the sintered CZISSe layer,29 potentially due to high recombination in the space-charge region, short carrier lifetime, low built-in voltage, or a combination of these effects. The recombination in the space charge region is likely a primary contributor, since the ideality of the cell was measured to be 1.7730. By evaluating the EQE response in the absorptionlimited region (i.e. wavelengths between 850 and 1050 nm wavelengths), the band gap is estimated to be 1.3 eV.31 Compared to the CIGSSe solar cells prepared by the solution methods (Ref 1: Voc = 0.63 V, Jsc = 28.8 mA/cm2, FF = 65.7%, A = 1.44; and Ref 3: Voc = 0.623 V, Jsc = 32.6 mA/cm2, FF =75%, A = 1.37) we find that the CZISSe solar cells have a greater Voc deficit (Eg/q-Voc) and lower fill factors. A higher value of the band gap (1.3 eV vs. ~1.1 eV for CIGSSe) along with lower EQE response contribute to the lower Jsc values. The Voc deficit for this solar cell is similar to the observed for CZTSSe solar cells and requires further exploration. However, our initial devices have achieved pce values similar to those reported for vacuum-deposited, indium-rich CZISe with the chalcopyrite structure reported in the literature.18 In summary, we have successfully synthesized alloyed CZIS nanocrystals of roughly 50% CuInS2 and 50% ZnS. Upon selenization, the CZIS nanocrystal films produce relatively pure-phase sintered CZISSe absorber layers. The high zinc content utilized in absorber formation causes the crystal grains to adopt a cubic zinc blende structure (rather than tetragonal chalcopyrite) and reduces the amount of indium needed. The best completed solar cell reaches a total area pce of 6.7%. The initial results from the zinc blende CZISSe solar cell demonstrate the viability of this class of materials as thin film absorbers and indicate that further study and optimization is merited.



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ASSOCIATED CONTENT Supporting Information. A detailed description of the synthesis, characterization methods used, and extra characterization of the nanocrystals. This information is available free of charge via the Internet at http://pubs.acs.org.

AUTHOR INFORMATION Corresponding Author * E-mail: [email protected] (R.A.)

ACKNOWLEDGMENT B.K.G. is thankful for the support of the GAANN program. (P200A090320-10) The authors also gratefully acknowledge the funding of NSF Solar Economy IGERT (0903670-DGE) and DOE SunShot (DE-EE0005328). C.K.M. acknowledges this work’s support by the National Science Foundation under grant no. DGE-0833366. E.A.S. acknowledges support to the Center for Functional Nanomaterials, Brookhaven National Laboratory by the US DOE Office of BasicEnergy Sciences (contract no. DEAC02-98CH10886). The authors acknowledge Xin Zhao for helping to acquire HRTEM images of the nanocrystals and assisting with the interpretation of the data.

REFERENCES (1) Guo, Q.; Ford, G. M.; Agrawal, R.; Hillhouse, H. W. Prog. Photovoltaics Res. Appl. 2013, 21, 64–71. (2) Jackson, P.; Hariskos, D.; Lotter, E.; Paetel, S.; Wuerz, R.; Menner, R.; Wischmann, W.; Powalla, M. Prog. Photovoltaics Res. Appl. 2011, 19, 894–897. (3) Todorov, T.; Gunawan, O.; Gokmen, T.; Mitzi, D. B. Prog. Photovoltaics Res. Appl. 2013, 21, 82–87. (4) Reinhard, P.; Pianezzi, F.; Kranz, L.; Nishiwaki, S.; Chirilă, A.; Buecheler, S.; Tiwari, A. N. Prog. Photovoltaics Res. Appl. 2013, n/a–n/a. (5) Rau, U.; Mattheis, J.; Kurth, M.; Schlo, T.; Jackson, P.; Wu, R.; Bilger, G. Prog. Photovoltaics Res. Appl. 2007, 15, 507–519. (6) Contreras, M. A.; Egaas, B.; Ramanathan, K.; Hiltner, J.; Swartzlander, A.; Hasoon, F.; Noufi, R. Prog. Photovoltaics Res. Appl. 1999, 316, 311–316. (7) Gloeckler, M.; Sankin, I.; Zhao, Z. Photovoltaics, IEEE J. 2013, 3, 1389–1393. (8) Green, M.; Emery, K.; Hishikawa, Y.; Warta, W.; Dunlop, E. D. Prog. Photovoltaics Res. Appl. 2012, 22, 1–9. (9) Wang, W.; Winkler, M. T.; Gunawan, O.; Gokmen, T.; Todorov, T. K.; Zhu, Y.; Mitzi, D. B. Adv. Energy Mater. 2013, n/a– n/a. (10) Guo, Q.; Ford, G. M.; Yang, W. C.; Walker, B. C.; Stach, E. A.; Hillhouse, H. W.; Agrawal, R. J. Am. Chem. Soc. 2010, 17384– 17386. (11) Miskin, C. K.; Yang, W.; Hages, C. J.; Carter, N. J.; Joglekar, C. S.; Stach, E. A.; Agrawal, R. Prog. Photovoltaics Res. Appl. 2014, 57. (12) Scragg, J. J. S.; Choubrac, L.; Lafond, A.; Ericson, T.; Platzer-björkman, C.; Lafond, A.; Ericson, T.; Scragg, J. J. S. Appl. Phys. Lett. 2014, 041911, 10–14. (13) Repins, I.; Beall, C.; Vora, N.; DeHart, C.; Kuciauskas, D.; Dippo, P.; To, B.; Mann, J.; Hsu, W.-C.; Goodrich, A.; Noufi, R. Sol. Energy Mater. Sol. Cells 2012, 101, 154–159. (14) Katagiri, H.; Jimbo, K.; Maw, W. S.; Oishi, K.; Yamazaki, M.; Araki, H.; Takeuchi, A. Thin Solid Films 2009, 517, 2455–2460. (15) Ping, F.; Guang-Xing, L.; Zhuang-Hao, Z.; Xing-Min, C.; Dong-Ping, Z. Chinese Phys. Lett. 2010, 27, 046801. (16) Unni, C.; Philip, D.; Gopchandran, K. G. Opt. Mater. (Amst). 2009, 32, 169–175. (17) Wagner, G.; Lehmann, S.; Schorr, S.; Spemann, D.; Doering, T. J. Solid State Chem. 2005, 178, 3631–3638.

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(18) Gremenok, V. F.; Zaretskaya, E. P.; Siarheyeva, V. M.; Bente, K.; Schmitz, W.; Zalesski, V. B.; Möller, H. J. Thin Solid Films 2005, 487, 193–198. (19) Tseng, Y. H.; Yang, C. S.; Wu, C. H.; Chiu, J. W.; Yang, M. De; Wu, C.-H. J. Cryst. Growth 2013, 378, 158–161. (20) Liu, Y.; Huang, F.; Xie, Y.; Cui, H.; Zhao, W.; Yang, C.; Dai, N. J. Phys. Chem. C 2013, 117, 10296–10301. (21) Zhang, J.; Xie, R.; Yang, W. Chem. Mater. 2011, 23, 3357–3361. (22) Xiang, W.-D.; Yang, H.-L.; Liang, X.-J.; Zhong, J.-S.; Wang, J.; Luo, L.; Xie, C.-P. J. Mater. Chem. C 2013, 1, 2014. (23) Zhang, W.; Zhong, X. Inorg. Chem. 2011, 50, 4065–4072. (24) Panthani, M. G.; Khan, T. A.; Reid, D. K.; Hellebusch, D. J.; Rasch, M. R.; Maynard, J. A.; Korgel, B. A. Nano Lett. 2013, 4294−4298. (25) . In a typical CuZnInS4 synthesis, the reaction vessel is charged with 14 mL of oleylamine, purged using standard procedures, then heated to 250°C . 384 mmol of Cu(acac)2, 0.416 mmol of Zn(acac)2 • xH20, 0.4 mmol of of In(acac)3, and 4 mL of oleylamine are injected into the flask along with 1.2 mmol of S in 2 mL of oleylamine. The reaction is held at 250°C for 15 min before cooling, washing, and collecting the product. See the Supporting Information for further detail on the synthesis procedure. (26) Li, S.; Zhao, Z.; Liu, Q.; Huang, L.; Wang, G.; Pan, D.; Zhang, H.; He, X. Inorg. Chem. 2011, 50, 11958–11964. (27) Denton, A. R.; Ashcroft, N. W. Phys. Rev. A 1991, 43, 3161–3164. (28) Guo, Q.; Ford, G. M.; Hillhouse, H. W.; Agrawal, R. Nano Lett. 2009, 9, 3060–3065. (29) Hegedus, S. S.; Shafarman, W. N. Prog. Photovoltaics Res. Appl. 2004, 12, 155–176. (30) Kirchartz, T.; Ding, K.; Rau, U. In Advanced Characterization Techniques for Thin Film Solar Cells; Abou-Ras, D.; Kirchartz, T.; Rau, U., Eds.; WILEY_VCH Verlag Gmbh & Co. KGaA: Weinheim, Germany, 2011; pp. 35–60. (31) Zoppi, G.; Forbes, I.; Miles, R. Prog. Photovoltaics Res. Appl. 2009, 315–319.


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Figure 1 (a) STEM-HAADF image of the CZIS nanocrystals, (b) PXRD pattern of the CZIS nanocrystals with CuInS (JCPDS: 27-159) and ZnS (JCPDS: 5-566) standards shown for reference (c) STEM-EDS map of nanocrystals (d) Size distribution of the nano-crystals. 58x46mm (600 x 600 DPI)


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Figure 2 (a) XRD pattern of the CZISSe films and (b) a close up of the scan in the vicinity of 53° and its single peak fit corresponding to the 311 plane. CISe (JCPDS: 40-1487) and ZnSe (JCPDS: 37-1463) standards are shown for reference. 34x16mm (600 x 600 DPI)



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Figure 3 (a) SEM cross sectional image of a selenized film (b) cross sectional EDX mapping of the elements: copper, zinc, indium, selenium, and carbon. 57x47mm (600 x 600 DPI)


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Figure 4 Vertical SEM-EDS linescan of a selenized film. 59x61mm (600 x 600 DPI)



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Figure 5 J-V characterization for devices made. Insert: table of parameters for the best performing device and EQE data for the device made from our synthesis. 55x38mm (600 x 600 DPI)


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29x11mm (600 x 600 DPI)


Synthesis of (CuInS2)0.5(ZnS)0.5 Alloy Nanocrystals and Their Use

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