Preparation of In2S3 and Cu-Doped In2S3 2D Ultrathin Nanoflakes with Tunable Absorption and Intense Pho-tocurrent Response
WANG Pengfei, CHEN Kai, PAN Guiming, XIE Ying, ZHOU LiSchool of Physics and Technology, Wuhan University, Wuhan 430072, Hubei, China
We reported an effective method to synthesize In2S3 and Cu-doped In2S3 two-dimensional ultrathin nanoflakes by the hydrothermal method through tuning the Cu/In molar ratio. The transmission electron microscope images showed that the products had ultrathin flake-like shape with wrinkling and rolling. The X-ray diffraction patterns indicated the crystal phase of nanoflakes was varied from β-In2S3 to tetragonal-CuInS2 as the Cu/In molar ratio was increased. The In2S3 nanoflakes exhibited absorption band at 450 nm, while new absorption peaks in turn appeared at 550 nm and 670 nm as the Cu/In molar ratio was increased. In addition, the two-dimensional ultrathin nanoflakes exhibited intense photocurrent response.
Key words:ultrathin nanoflakes; Cu doping; crystal phase; absorption; photocurrent
 Cao G X, Zhao Y B, Wu Z S. Synthesis and characterization of In2S3 nanoparticles [J]. Journal of Alloys and Compounds, 2009, 472(1-2): 325-327.
 Yan C, Liu F Y, Song N, et al. Band alignments of different buffer layers (CdS, Zn(O,S), and In2S3) on Cu2ZnSnS4 [J]. Applied Physics Letters, 2014, 104(17): 173901.
 Xiong X, Zhang Q, Gan L, et al. Geometry dependent photoconductivity of In2S3 kinks synthesized by kinetically controlled thermal deposition [J]. Nano Research, 2016, 9 (12): 3848-3857.
 Siol S, Dhakal T P, Gudavalli G S, et al. Combinatorial reactive sputtering of In2S3 as an alternative contact layer for thin film solar cells [J]. ACS Applied Materials & Interfaces, 2016, 8(22): 14004-14011.
 Chen W, Bovin J O, Joly A G, et al. Full-color emission from In2S3 and In2S3:Eu3+ nanoparticles [J]. The Journal of Physical Chemistry B, 2004, 108(32): 11927-11934.
 Wang L G, Xia L, Wu Y J, et al. Zr-doped β-In2S3 ultrathin nanoflakes as photoanodes: Enhanced visible-light-driven photoelectrochemical water splitting [J]. ACS Sustainable Chemistry & Engineering, 2016, 4(5): 2606-2614.
 Yao B B, Zhao R, Lu S Y, et al. Quantum phase transition from superparamagnetic to quantum superparamagnetic state in In2S3:Eu nanoparticles [J]. RCS Advances, 2013, 3(33): 13878- 13883.
 Rodriguez-Hernandez P E, Nieto-Zepeda K E, Guillén- Cervantes A, et al. Structural and optical properties of In2S3 thin films grown by chemical bath deposition on pet flexible substrates [J]. Chalcogenide Letters, 2017, 14(8): 331-335.
 Kim T W, Park H, Bae H, et al. Sulfurization-induced growth of single-crystalline high-mobility β-In2S3 films on InP [J]. AIP Advances, 2017, 7(12): 125109.
 Bi K, Sui N, Wang Y H, et al. Temperature-dependent charge carrier dynamics investigation of heterostructured Cu2S-In2S3 nanocrystals films using injected charge extraction by linearly increasing voltage [J]. Applied Physics Letters, 2017, 110(8): 083104.
 Kim J, Hiroi H, Todorov T K, et al. High efficiency Cu2ZnSn (S, Se)4 solar cells by applying a double In2S3/CdS emitter [J]. Advanced Materials, 2014, 26(44): 7427-7431.
 John T T, Mathew M, Kartha C S, et al. CuInS2/In2S3 thin film solar cell using spray pyrolysis technique having 9.5% efficiency [J]. Solar Energy Materials and Solar Cells, 2005, 89(1): 27-36.
 Zhou J, Tian G H, Chen Y J, et al. Growth rate controlled synthesis of hierarchical Bi2S3/In2S3 core/shell microspheres with enhanced photocatalytic activity [J]. Scientific Reports, 2014, 4(2955): 4027.
 Li H J, Gao Y Y, Zhou Y, et al. Construction and nanoscale detection of interfacial charge transfer of elegant Z-scheme WO3/Au/In2S3 nanowire arrays [J]. Nano Letters, 2016, 16(9): 5547-5552.
 Fu X L, Wang X X, Chen Z X, et al. Photocatalytic performance of tetragonal and cubic β-In2S3 for the water splitting under visible light irradiation [J]. Applied Catalysis B: Environmental, 2010, 95(3-4): 393-399.
 Chen L Y, Zhang Z D, Wang W Z. Self-assembled porous 3D flowerlike β-In2S3 structures: Synthesis, characterization, and optical properties [J]. The Journal of Physical Chemistry C, 2008, 112(11): 4117-4123.
 Steigmann G A, Sutherland H H, Goodyear J. The crystal structure of β-In2S3 [J]. Acta Crystallographica, 1965, 19(6): 967-971.
 Cherian A S, Mathew M, Kartha C S, et al. Role of chlorine on the opto-electronic properties of β-In2S3 thin films [J]. Thin Solid Films, 2010, 518(7): 1779-1783.
 Jayakrishnan R, Sebastian T, Sudha kartha C, et al. Effect of defect bands in β-In2S3 thin films [J]. Journal of Applied Physics, 2012, 111(9): 093714.
 Choe S H, Bang T H, Kim N O, et al. Optical properties of β-In2S3 and β-In2S3:Co2+ single crystals [J]. Semiconductor Science and Technology, 2001, 16(2): 98-102.
 Maha M H Z, Bagheri-Mohagheghi M M, Azimi-Juybari H. Tin doped β-In2S3 thin films prepared by spray pyrolysis: Correlation between structural, electrical, optical, thermoelectric and photoconductive properties [J]. Thin Solid Films, 2013, 536(1): 57-62.
 Yao B B, Wang P, Wang S M, et al. Ce doping influence on the magnetic phase transition in In2S3:Ce nanoparticles [J]. CrystEngComm, 2014, 16(13): 2584-2588.
 Tapia C, Berglund S P, Friedrich D, et al. Synthesis and characterization of V-doped β-In2S3 thin films on FTO substrates [J]. The Journal of Physical Chemistry C, 2016, 120(50): 28753-28761.
 Tang J, Konstantatos G, Hinds S, et al. Heavy-metal-free solution-processed nanoparticle-based photodetectors: Doping of intrinsic vacancies enables engineering of sensitivity and speed [J]. ACS Nano, 2009, 3(2): 331-338.
 Chen B K, Chang S, Li D, et al. Template synthesis of CuInS2 nanocrystals from In2S3 nanoplates and their application as counter electrodes in dye-sensitized solar cells [J]. Chemistry of Materials, 2015, 27(17): 5949-5956.
 Liu L, Liu H J, Kou H Z, et al. Morphology control of β-In2S3 from chrysanthemum-like microspheres to hollow microspheres: Synthesis and electrochemical properties [J]. Crystal Growth & Design, 2009, 9(1): 113-117.
 Peng S J, Liang J, Zhang L, et al. Shape-controlled synthesis and optical characterization of chalcopyrite CuInS2 microstructures [J]. Journal of Crystal Growth, 2007, 305(1): 99- 103.