RSC Advances COMMUNICATION

7 downloads 215 Views 515KB Size Report
345 mV and Jsc of 0.2 mA cmJ2 without any optimization of the thickness and electrical ... on 07/05/2016 11:49:39. View Article Online / Journal Homepage / Table of Contents for this issue .... Seo, Y. Choi and B-H. Ryu, Energy Environ.
View Article Online / Journal Homepage / Table of Contents for this issue

RSC Advances

Dynamic Article Links

Cite this: RSC Advances, 2012, 2, 10481–10484 www.rsc.org/advances

COMMUNICATION

Solution-based synthesis of chalcostibite (CuSbS2) nanobricks for solar energy conversion{

Published on 04 September 2012. Downloaded on 07/05/2016 11:49:39.

Chang Yan,a Zhenghua Su,a Ening Gu,a Tiantian Cao,a Jia Yang,a Jin Liu,a Fangyang Liu,*a Yanqing Lai,*b Jie Lia and Yexiang Liua Received 25th July 2012, Accepted 4th September 2012 DOI: 10.1039/c2ra21554c

Chalcostibite brick-like nanoparticles have been synthesized using hot-injection method in coordinating solvents. The CuSbS2 nanobricks possess a band gap of 1.40 eV and the corresponding nanobrick-electrode shows an IPCE of 5%–15% in the visible region. Our work demonstrates CuSbS2 nanobricks have potential in the field of solar energy conversion. Ternary chalcostibite CuSbS2 is an emerging semiconductor that is considered as a potential low-cost light-absorbing material for thin film photovoltaics. CuSbS2 possesses a near-optimal direct band gap in the range of 1.38–1.52 eV, a strong light absorption (a >104 cm21 for hv >1.3 eV) and a suitable electrical property, which are essential for solar cell application.1 Also, this material is indicated as a promising alternative to CuInxGa12xSe2 (CIGS) and CdTe, because it has relatively non-toxic compositions and the price of antimony is much lower than that of indium.1b,2 So, it has received increasing amounts of attention and various film-fabricating approaches for CuSbS2 have been reported such as spray pyrolysis,2a,3 direct evaporation,4 chemical bath deposition,5 sulfurization of the electrodeposited Cu-Sb precursor,6 and thermal evaporated Sb2S3/ Cu layers.1b A preliminary photovoltaic cell has been demonstrated as SnO2:F-(n)CdS:In-(i)Sb2S3-(p)CuSbS2-Ag, presenting a Voc of 345 mV and Jsc of 0.2 mA cm22 without any optimization of the thickness and electrical property of the absorber layer.7 Synthesis of CuSbS2 nanoparticles (including round, triangular nanocrystals, nanorods, nanobricks etc.) is attractive and significant owing to its perspective to conveniently produce large-area solar cells at low cost by the roll-to-roll method utilizing corresponding nanoparticle-ink or paint. Compared with traditional physical vapor a School of Metallurgical Science and Engineering, Central South University, Changsha, China. E-mail: [email protected]; Fax: +86 731 88876454; Tel: +86 731 88876454 b Engineering Research Center of High Performance Battery Materials and Devices, Research Institute of Central South University in Shenzhen, Shenzhen, 518057, China. E-mail: [email protected]; Fax: +86 13975808172; Tel: +86 13975808172 { Electronic Supplementary Information (ESI) available: Experimental details. Materials characterization. Additional large scale TEM image, Fast Fourier Transform (FFT) pattern of as-synthesized CuSbS2. Simulated CuSbS2 single crystal electron diffraction data. SAED and EDX data of assynthesized CuSbS2 nanobricks. SEM images, XRD, IR data and electrical properties for the CuSbS2 films before and after annealing. Transient photocurrent spectrum for the prepared CuSbS2 films. See DOI: 10.1039/ c2ra21554c

This journal is ß The Royal Society of Chemistry 2012

deposition (PVD) method, the nanoparticle-ink painting approach possesses the merits of low cost and excellent fabrication scalability.8 Therefore, syntheses of photovoltaic nanoparticles arouse great interest not only for conventional industrialized photovoltaic compounds (CdTe,9 CIGS10), but also for potential and/or new emerging semiconductor compounds (CZTS(Se),11 FeS2,12 SnS(Se),13 CTSe,14 CFTS15) that can be utilized in solar cells applications. Recently Embden and Tachibana reported the synthesis of Famatinite (Cu3SbS4) nanocrystals.16 CuSbS2 particles in millimeter scale and CuSbS2 quasi-nanorod were synthesized by solvothermal and hydrothermal methods, respectively.1e,17 Here we present the colloidal route to synthesize high-quality CuSbS2 nanobricks in oleylamine (OLA). The obtained CuSbS2 nanobricks can be dispersed in toluene, forming an ink. The chalcostibite film electrodes were prepared by drop-casting the ink onto an ITO substrate. A photoelectrochemical cell is established to evaluate the potential viability of the CuSbS2 nanobricks for photovoltaics. A notable photocurrent and an incident photo to current efficiency (IPCE) ranging from 5% to 15% in the visible region are obtained using the chalcostibite electrode, demonstrating the promising prospects of CuSbS2 nanobricks in the application of solar energy conversion. The syntheses of CuSbS2 nanobricks were carried out utilizing hot-injection method on a standard air-inert Schlenk line. Briefly, Sulfur was dissolved in OLA completely using ultrasonic method,11c gaining a S/OLA solution in red-orange color. Then the S/OLA solution was quickly injected to the hot solution of OLA containing stoichiometric amount of copper(II) acetylacetonate and antimony(III) acetate [atom ratio Cu : Sb = 1] at 230 uC for 1 h under an Ar atmosphere. Full experimental details can be found in the Supporting Information (ESI{). Fig. 1 demonstrates basic structural characterization of as-synthesized nanobricks. They are cuboid shaped (y50–120 nm in length, y20–40 nm in width and y6–9 nm in thickness) as indicated in the low-magnification TEM images (Fig. 1a and 1b, additional large scale TEM image is included in ESI{). A high-resolution TEM (HRTEM) image (Fig. 1c) displays a clear crystalline surface with the interplanar spacing of 3.2 and ˚ corresponding to the (111) and (2–13) plane of CuSbS2, 2.1 A respectively. Additionally, an angle of approximately 89.7u between the two planes is carefully measured, matching very well with the corresponding angle (89.6u) of previous structural data reported for bulk chalcostibite,18 giving nano-scale evidence that the synthesized RSC Adv., 2012, 2, 10481–10484 | 10481

Published on 04 September 2012. Downloaded on 07/05/2016 11:49:39.

View Article Online

Fig. 1 (a) and (b) are low-magnitude TEM images of as-synthesized nanobricks. (c) High resolution TEM image of a certain nanobrick and (d) the corresponding FFT pattern. The nanobrick is imaged down the [24 1 3] crystallographic zone axis. (e) XRD pattern of the prepared nanobricks. As a reference, the diffraction pattern of chalcostibite pattern (JCPDS no. 88-0822) is shown. (f) UV-VIS-NIR spectroscopic characterization of the CuSbS2 nanobricks.

nanobricks possess the structure of chalcostibite. Fast Fourier Transform (FFT) pattern of the HRTEM (Fig. 1d) matches well with simulated electron diffraction using previously reported CuSbS2 structure data18 by Crystalmaker software (simulated patterns and detailed discussion is given in ESI{). The lattice data calculated from selected area electron diffraction (SAED) pattern of randomly chosen region of CuSbS2 nanobricks corresponds to the lattice parameters for CuSbS2 (See ESI{, Fig. S3). The XRD pattern of the as-prepared nanobricks reveals that they crystallized in orthorhombic phase (Pnma) and correspond well to chalcostibite structure (JCPDS 88-0822). The elemental composition of as-synthesized CuSbS2 nanobricks determined by Energy Dispersive X-ray spectroscopy (EDX) is Cu0.86Sb1.05S2 (See ESI{, Fig. S4), which is copper poor. The UV-VIS-NIR spectrum (Fig. 1f) of nanobricks shows a slow absorption rise with a platform ranged from 400–600 nm. A band gap of CuSbS2 nanobricks is estimated to be 1.40 eV via 10482 | RSC Adv., 2012, 2, 10481–10484

extrapolating the linear region of the plot of (ahv)2 versus photon energy (hv) as illustrated in the inset of Fig. 1f. The band gap value is close to the previous literature for bulk CuSbS2. To explore the possible pathway for the formation of CuSbS2 nanobricks, the phase data for the reaction products at different times were investigated by XRD (See Fig. S5{). CuSbS2 phase is produced in the initial stage, however, both CuS (Covellite) and Sb2S3 (stibnite) are detected. As the reaction goes on, peaks assigned to CuS and Sb2S3 gradually disappear. The remaining peaks are attributed to CuSbS2, suggesting that CuS and Sb2S3 would be the intermediates involved in the formation of CuSbS2. Copper chalcogenide phase seems to be a regular intermediate for the synthesis of copper-containing ternary or quaternary chalcogenide in OLA,15a,19 which may be due to Cu chalcogenide being kinetically more favorable than the ternary or quaternary target products. In addition, experiments at different reaction (injection) temperatures This journal is ß The Royal Society of Chemistry 2012

Published on 04 September 2012. Downloaded on 07/05/2016 11:49:39.

View Article Online

have been trialled: the products at low synthetic temperature (180 uC) are mainly binary phases (CuS); High temperature (280 uC) injection and reaction lead to uncontrolled growth of CuSbS2 and severe aggregation of the products. Photovoltaic performance of new light-absorber materials can be readily tested in a photoelectrochemical (PEC) cell. This method is popular because the liquid electrolyte provides nearly ideal contact to the half cell, avoiding problems such as interface contact with the full device architecture.20 Also, it allows rapid characterization of the absorber layer. Therefore, in order to assess the photoactivity and PV-potential of CuSbS2 thin films fabricated by nanoink painting route, the photoelectrochemical characterization was carried out in an aqueous PEC cell containing 0.5 M H2SO4. The ink containing CuSbS2 bricks was directly drop-casted on the ITO electrode and then annealed in a flowing Ar atmosphere at 350 uC for 30 min to remove the insulating ligands as well as enhance the electrical conductivity of the obtained films.11d The composition and crystallographics do not change much with the annealing treatment (the SEM images, XRD, FTIR data and electrical properties for the films before and after annealing are given in the ESI{). Fig. 2(a) displays

the current density versus voltage plots for the prepared CuSbS2 films utilizing chopping method (10 s light on, 10 s light off). The film demonstrates a gradual photo-enhancement effect in the negative potential direction upon illumination, exhibiting a characteristic of a semiconductor with p-type conductivity.20 As for p-type semiconductor materials, electrons are transferred from the conduction band to the oxidant in solution, and then from the back contact (here ITO) into the semiconductor, leading to the observed reductive current.14,20a The photocurrent density reaches a saturated value of about 0.09 mA cm22 at 20.2 V vs. SCE. The transient photocurrent at this voltage is obtained, showing good photostability of nanoinkcasting CuSbS2 film over many cycles (24 cycles demonstrated here, see Fig. S9{). The magnitude of the gained photoresponse is high enough to acquire the IPCE spectrum, as shown in Fig. 2(b). Approximately 5%–15% of the incident photons can be readily converted to electron and hole pairs in the wavelength region of 400– 800 nm that covers most of the visible light. The IPCE value reaches zero when the photon energy goes below 1.48 eV, indicating its band gap value is around 1.48 eV, which corresponds to the UV-VIS-NIR data. In summary, a facile colloidal synthesis of CuSbS2 nanobricks by a simple hot-injection method is described. The structure of prepared CuSbS2 nanobricks is confirmed by XRD, SAED pattern, latticeresolution TEM image, and the corresponding FFT pattern. A band gap of 1.40 eV is obtained from the UV-VIS-NIR data. Possible intermediates, CuS and Sb2S3, are found during the synthesis process of CuSbS2 in OLA. The film prepared by casting the ink containing CuSbS2 nanobricks demonstrates a notable and stable photoresponse. About 5%–15% of the visible light can be converted to electron and hole pairs in the PEC cell using the CuSbS2 electrode. This work shows that CuSbS2 nanobricks have potential in the field of solar energy conversion (e.g., water splitting or solar cell). Future work will focus on the utilization of CuSbS2 nanobricks for photovoltaic devices.

Acknowledgements We acknowledge Dr Guo Qijie of Purdue University for his advice and help in hot-injection experiments. This work was supported by the National High Technology Research and Development Program of China (863 Program, Grant No. 2012AA050703), the Fundamental Research Funds for the Central Universities (Grant No. 201021100029 and 2012QNZT022) and the National Natural Science Foundation of China (Grant No. 51272292).

References

Fig. 2 (a) Photocurrent density and potential spectrum of the CuSbS2 films prepared via nanobricks-ink painting route. The photocurrent was obtained in 0.5 M H2SO4 solution using 100 mW cm22 chopped illumination. All potential values are given vs. SCE. (b) Incident photo to current efficiency (IPCE) spectrum of prepared CuSbS2 film.

This journal is ß The Royal Society of Chemistry 2012

1 (a) A. Rabhi, M. Kanzari and B. Rezig, Mater. Lett., 2008, 62, 3576; (b) C. Garza, S. Shaji, A. Arato, E. Perez Tijerina, G. Alan Castillo, T. K. Das Roy and B. Krishnan, Sol. Energy Mater. Sol. Cells, 2011, 95, 2001; (c) D. Colombara, L. M. Peter, K. D. Rogers, J. D. Painter and S. Roncallo, Thin Solid Films, 2011, 519, 7438; (d) Y. Rodriguez Lazcano, M. T. S. Nair and P. K. Nair, J Cryst Growth, 2001, 223, 399; (e) J. Zhou, G. Q. Bian, Q. Y. Zhu, Y. Zhang, C. Y. Li and J. Dai, J Solid State Chem, 2009, 182, 259; (f) A. Rabhi and M. Kanzari, Chalcogenide Lett., 2011, 8, 383; (g) J. T. R. Dufton, A. Walsh, P. M. Panchmatia, L. M. Peter, D. Colombara and M. Saiful Islam, Phys. Chem. Chem. Phys., 2012, 14, 7229. 2 (a) S. A. Manolache, L. Andronic, A. Duta and A. Enesca, J Optoelectron Adv M, 2007, 9, 1269; (b) Price information for Metals in Shang Hai Metals Market. URL: 3164988.html.

RSC Adv., 2012, 2, 10481–10484 | 10483

Published on 04 September 2012. Downloaded on 07/05/2016 11:49:39.

View Article Online

3 (a) S. A. Manolache, A. Duta and A. Enesca, J Optoelectron Adv M, 2007, 9, 3219; (b) S. Manolache, A. Duta, L. Isac, M. Nanu, A. Goossens and J. Schoonman, Thin Solid Films, 2007, 515, 5957. 4 A. Rabhi, M. Kanzari and B. Rezig, Thin Solid Films, 2009, 517, 2477. 5 S. C. Ezugwu, F. I. Ezema and P. U. Asogwa, Chalcogenide Lett., 2010, 7, 341. 6 D. Colombara, L. M. Peter, K. D. Rogers and K. Hutchings, J Solid State Chem., 2012, 186, 36. 7 Y. Rodriguez-Lazcano, M. T. S. Nair and P. K. Nair, J. Electrochem. Soc., 2005, 152, G635. 8 S. E. Habas, H. A. S. Platt, M. F. A. M. Hest and D. S. Ginley, Chem. Rev., 2010, 110, 6571. 9 I. Gur, N. A. Fromer, M. L. Geier and A. P. Alivisatos, Science, 2005, 310, 462. 10 (a) Q. Guo, S. J. Kim, M. Kar, W. N. Shafarman, R. W. Birkmire, E. A. Stach, R. Agrawal and H. W. Hillhouse, Nano Lett., 2008, 8, 2982; (b) Q. Guo, G. M. Ford, H. W. Hillhouse and R. Agrawal, Nano Lett., 2009, 9, 3060; (c) M. G. Panthani, V. Akhavan, B. Goodfellow, J. P. Schmidtke, L. Dunn, A. Dodabalapur, P. F. Barbara and B. A. Korgel, J. Am. Chem. Soc., 2008, 130, 16770; (d) J. Tang, S. Hinds, S. O. Kelley and E. H. Sargent, Chem. Mater., 2008, 20, 6906; (e) Q. J. Guo, G. M. Ford, R. Agrawal and H. W. Hillhouse, Prog. Photovolt: Res. Appl., 2012, DOI: 10.1002/pip.2200; (f) V. A. Akhavan, B. W. Goodfellow, M. G. Panthani, D. K. Reid, D. J. Hellebusch, T. Adachi and B. A. Korgel, Energy Environ. Sci., 2010, 3, 1600; (g) S. Jeong, B-S. Lee, S. J. Ahn, K. H. Yoon, Y-H. Seo, Y. Choi and B-H. Ryu, Energy Environ. Sci., 2012, 5, 7539. 11 (a) Q. Guo, H. W. Hillhouse and R. Agrawal, J. Am. Chem. Soc., 2009, 131, 11672; (b) C. Steinhagen, M. G. Panthani, V. Akhavan, B. Goodfellow, B. Koo and B. A. Korgel, J. Am. Chem. Soc., 2009, 131, 12554; (c) S. C. Riha, B. A. Parkinson and A. L.Prieto, J. Am. Chem. Soc., 2009, 131, 12054; (d) X. T. Lu, Z. B. Zhuang, Q. Peng and Y. D. Li, Chem.

10484 | RSC Adv., 2012, 2, 10481–10484

12 13

14 15

16 17 18 19 20

Commun., 2011, 47, 3141; (e) S. C. Riha, B. A. Parkinson and A. L. Prieto, J. Am. Chem. Soc., 2011, 133, 15272; (f) A. Shavel, J. Arbiol and A. Cabot, J. Am. Chem. Soc., 2010, 132, 4514. (a) J. Puthussery, S. Seefeld, N. Berry, M. Gibbs and M. Law, J. Am. Chem. Soc., 2011, 133, 716; (b) Y. Bi, Y. B. Yuan, C. L. Exstrom, S. A. Darveau and J. S. Huang, Nano Lett., 2011, 11, 4953. (a) S. G. Hickey, C. Waurisch, B. Rellinghaus and A. Eychmuu¨ller, J. Am. Chem. Soc., 2008, 130, 14978; (b) M. A. Franzman, C. W. Schlenker, M. E. Thompson and R. L. Brutchey, J. Am. Chem. Soc., 2010, 132, 4060; (c) W. J. Baumgardner, J. J. Choi, Y.-F. Lim and T. Hanrath, J. Am. Chem. Soc., 2010, 132, 9519; (d) P. D. Antunez, J. J. Buckley and R. L. Brutchey, Nanoscale, 2011, 3, 2399. J. Puthussery, S. Seefeld, N. Berry, M. Gibbs and M. Law, J. Am. Chem. Soc., 2012, 134, 23. (a) C. Yan, C. Huang, J. Yang, F. Liu, J. Liu, Y. Lai, J. Li and Y. Liu, Chem. Commun., 2012, 48, 2603; (b) X. Y. Zhang, N. Z. Bao, K. Ramasamy, Y. H. A. Wang, Y. F. Wang, B. P. Lin and A. Gupta, Chem. Commun., 2012, 48, 4956; (c) L. Li, X. Y. Liu, J. Huang, M. Cao, S. Y. Chen, Y. Shen and L. J. Wang, Mater. Chem. Phys., 2012, 133, 688. J. V. Embden and Y. Tachibana, J. Mater. Chem., 2012, 22, 11466. C. H. An, Q. C. Liu, K. B. Tang, Q. Yang, X. Y. Chen, J. W. Liu and Y. T. Qian, J. Crys. Growth., 2003, 256, 128. A. Kyono and M. Kimata, Am Mineral., 2005, 90, 162. (a) M. Kar, R. Agrawal and H. W. Hillhouse, J. Am. Chem. Soc., 2011, 133, 17239; (b) A. Shavel, D. Cadavid, M. Ibanez, A. Carrete and A. Cabot, J. Am. Chem. Soc., 2012, 134, 1438. (a) H. Ye, H. S. Park, V. A. Akhavan, B. W. Goodfellow, M. G. Panthani, B. A. Korgel and A. J. Bard, J. Phys. Chem. C, 2011, 115, 234; (b) V. A. Akhavan, B. W. Goodfellow, M. G. Panthani, C. Steinhagen, T. B. Harvey, C. J. Stolle and B. A. Korgel, J Solid State Chem, 2012, 189, 2.

This journal is ß The Royal Society of Chemistry 2012