Structural, Optical, and Photoelectrochemical Evaluation of TiO2 /SnO2 /Zn0.3Cd0.7S Multilayer Heterostructures for Enhanced Solar-driven Applications
J. Environ. Nanotechnol., Volume 14, No 4 (December 2025) pp. 463-480
Abstract
This study presents the fabrication and characterization of a multilayer TiO2/SnO2/Zn0.3Cd0.7S thin film heterostructure for optoelectronic applications. This heterostructure system was prepared by thermochemical decomposition method. Structural analysis via X-ray diffraction (XRD) confirmed the polycrystalline nature of the films with distinguishable peaks for each constituent layer. The incorporation of Zn0.3Cd0.7S into the TiO2/SnO2 system led to a reduction in crystallite size and an increase in microstrain, suggesting enhanced lattice distortion and interfacial stress conducive to charge separation. Surface morphology assessed through SEM and AFM revealed uniform grain distribution and improved film compactness in the heterostructure. Optical characterizations conducted by UV-Vis absorption spectroscopy and Tauc analysis revealed that the band gap energy in the pristine SnO and TiO material was 3.20 eV and 3.10 eV, respectively and reduced to 2.25 eV in the resulting composite, which improves the visible light absorption. The refractive index and extinction coefficient were improved in the heterostructured film, and light interaction with matter also improved. Mott-Schottky analysis revealed that all samples are n-type with TiO2/SnO2/Zn0.3Cd0.7S having a higher flat-band potential (+0.22 V) and lower donor concentration. Such shifts indicate a better band bending and carrier separation. Under illumination, the I-V characteristics showed an increase in photocurrent and a reduction in the dark current in the heterostructure, emphasizing its enhanced photoelectrochemical performance. The overall multilayer TiO2/SnO2/Zn0.3Cd0.7S system has desirable structural, optical, and electronic characteristics, rendering it a feasible next-generation photovoltaic and photoelectrochemical application.
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Reference
Achi, A. A., Universal Pharmaceutical Calculations: An Overview, Clin. Pharmacol. Biopharm., 6, e127 (2017).
https://doi.org/10.4172/2167-065X.1000e127
Ahmad, A. A., Migdadi, A. B. and Bataineh, A. M. Q., Structural, optical, and electrical properties of strontium-doped tin dioxide films for high photoconductivity, Thin Solid Films, 796, 140312 (2024).
https://doi.org/10.1016/j.tsf.2024.140312
Banerjee, A., The design, fabrication, and photocatalytic utility of nanostructured semiconductors: focus on TiO2-based nanostructures, Nanotechnol. Sci. Appl., 4, 35-65 (2011).
https://doi.org/10.2147/NSA.S9040
Bocarsly, B. A., Cava, R. and Frick, J. J., Chalcopyrite CuIn(S1–xSex)2 for Photoelectrocatalytic H2 Evolution: Unraveling the Energetics and Complex Kinetics of Photogenerated Charge Transfer in the Semiconductor Bulk, Chem. Mater., 30(13), 4422-4431 (2018).
https://doi.org/10.1021/acs.chemmater.8b01827
Chen, J., Lv, S., Shen, Z., Tian, P., Chen, J. and Li, Y., Novel ZnCdS Quantum Dots Engineering for Enhanced Visible-Light-Driven Hydrogen Evolution, ACS Sustainable Chem. Eng., 7(16), 13805-13814 (2019).
https://doi.org/10.1021/acssuschemeng.9b01632
Dahl, M., Liu, Y. and Yin, Y., Composite Titanium Dioxide Nanomaterials, Chem. Rev., 114(19), 9853-9889 (2014).
https://doi.org/10.1021/cr400634p
Danilyuk, L. A., Borisenko, E. V., Lu, C., Sidorova, T. N., Rusli, R. and Wang, H., An Enhanced Charge Carrier Separation in a Heterojunction Solar Cell with a Metal Oxide, Phys. Status Solidi A, 219, 2100525 (2022).
https://doi.org/10.1002/pssa.202100525
Devadoss, I., Sakthivel, P. and Krishnamoorthy, A., Band gap tailoring and photoluminescence performance of CdS quantum dots for white LED applications: influence of Ba2+ and Zn2+ ions, J. Mater. Sci.: Mater. Electron., 32(5), 5729-5737 (2021).
https://doi.org/10.1007/s10854-021-05293-y
Duan, C., Luo, W., Jiu, T., Li, J., Wang, Y. and Lu, F., Facile preparation and characterization of ZnCdS nanocrystals for interfacial applications in photovoltaic devices, J. Colloid Interface Sci., 512, 353-360, (2018).
https://doi.org/10.1016/j.jcis.2017.09.108
Elsherif, S. O., Muftah, A. E. G., Abubaker, O. and Dharmadasa, I. M., Structural, optical and electrical properties of SnO2:F thin films deposited by spray pyrolysis for application in thin film solar cells, J. Mater. Sci.: Mater. Electron., 27, 12280-12286 (2016).
https://doi.org/10.1007/s10854-016-5206-x
Ezema, I. F., Ezugwu, S., Nkele, C. A. and Suguyima, M., Structural and Electronic Properties of Metal Oxides and Their Applications in Solar Cells, Chem. Deposited Nanocryst. Metal Oxide Thin Films, 147-163 (2021).
https://doi.org/10.1007/978-3-030-68462-4_6
Feng, L., Ai, L., Wang, L., Guo, N., Xu, M., Leng, C., Ma, Q., Tan, C. and Shi, H., Constructing a Type-II CdS/Bi2MoO6 Heterostructure: Promoting Photocatalytic Degradation of Contaminants, Langmuir, 40(36), 18896-18905 (2024).
https://doi.org/10.1021/acs.langmuir.4c01143
Fu, Y. X., Xiao, X. F., Wei, Q. Z., Xiao, G., Mo, L. Q. and Hou, S., Fine Tuning of Charge Motion Over Homogeneous Transient Metal Chalcogenides Heterostructured Photoanodes for Photoelectrochemical Water Splitting, Chem. Eng. J., 433, 133641 (2022).
https://doi.org/10.1016/j.cej.2021.133641
Fujisawa, I. J., Eda, T. and Hanaya, M., Comparative study of conduction-band and valence-band edges of TiO2, SrTiO3, and BaTiO3 by ionization potential measurements, Chem. Phys. Lett., 685, 23-26, (2017).
https://doi.org/10.1016/j.cplett.2017.07.031
Gelderman, K., Lee, L. and Donne, W. S., Flat-Band Potential of a Semiconductor: Using the Mott Schottky Equation, J. Chem. Educ., 84(4), 685-688 (2007).
https://doi.org/10.1021/ed084p685
Ghosh, S., Sarkar, S., Das, K. B., Sen, D., Samanta, M. and Chattopadhyay, K. K., Band Edge Tuned ZnxCd1-xS Solid Solution Nanopowders for Efficient Solar Photocatalysis, Phys. Chem. Chem. Phys., 19(44), 29998-30009 (2017).
https://doi.org/10.1039/C7CP06305A
Hadke, S., Huang, M., Chen, C., Tay, F. H., Chen, S., Tang, J. and Wong, L., Emerging Chalcogenide Thin Films for Solar Energy Harvesting Devices, Chem. Rev., 122(11), 10170-10265 (2022).
https://doi.org/10.1021/acs.chemrev.1c00301
Han, A. M., Kim, J. H., Lee, C. H., Park, S. J. and Lee, N. H., Effects of porosity and particle size on the gas sensing properties of SnO2 films, Appl. Surf. Sci., 481, 133-137 (2019).
https://doi.org/10.1016/j.apsusc.2019.03.043
Hanaor, H. A. D. and Sorrell, C. C., Review of the anatase to rutile phase transformation, J. Mater. Sci., 46(4), 855-874 (2011).
https://doi.org/10.1007/s10853-010-5113-0
Haryński, Ł., Olejnik, A., Grochowska, K. and Siuzdak, K., A facile method for Tauc exponent and corresponding electronic transitions determination in semiconductors directly from UV–vis spectroscopy data, Opt. Mater., 127, 112205 (2022).
https://doi.org/10.1016/j.optmat.2022.112205
Hou, S., Li, S., Xiao, X. F., Xiao, G., Zhu, C. S. and Mo, L. Q., Precisely Modulating the Photosensitization Efficiency of Transition-Metal Chalcogenide Quantum Dots toward Solar Water Oxidation, lnorg. Chem., 61(32), 1188-1194 (2022).
https://doi.org/10.1021/acs.inorgchem.1c03550
Huang, Q. W., Wen, S., Hu, W., Huang, G. F. and Yang, K., Interfacial interaction in monolayer transition metal dichalcogenide/metal oxide heterostructures and its effects on electronic and optical properties: The case of MX2/CeO2, Appl. Phys. Express, 10, 011201 (2016).
https://doi.org/10.7567/APEX.10.011201
Iqbal, A. M., Ahmad, A., Malik, M., Choi, R. J. and Pham, V. P., Pressure-Induced Bandgap Engineering and Tuning Optical Responses of Cd0.25Zn0.75S Alloy for Optoelectronic and Photovoltaic Applications, Mater., 15(7), 2617 (2022).
https://www.mdpi.com/1996-1944/15/7/2617
Jayaraman, P. J., Velpula, M., Hamdan, M., Kaisare, S. N. and Chandiran, K. A., BiVO4/Cs2PtI6 Vacancy-Ordered Halide Perovskite Heterojunction for Panchromatic Light Harvesting and Enhanced Charge Separation in Photoelectrochemical Water Oxidation, ACS Appl. Mater. interfaces, 13(14), 16267-16278 (2021).
https://doi.org/10.1021/acsami.0c22654
Jolivet, A., Labbé, C., Frilay, C., Debieu, O., Marie, P., Horcholle, B., Lemarié, F., Portier, X., Grygiel, C., Duprey, S., Jadwisienczak, W., Ingram, D., Upadhyay, M., David, A., Fouchet, A., Lüders, U. and Cardin, J., Structural, optical, and electrical properties of TiO2 thin films deposited by ALD: Impact of the substrate, the deposited thickness and the deposition temperature, Appl. Surf. Sci., 608, 155214 (2023).
https://doi.org/10.1016/j.apsusc.2022.155214
Kang, M., Kim, W. S. and Park, Y. H., Optical properties of TiO2 thin films with crystal structure, J. Phys. Chem. Solids, 123, 266-270 (2018).
https://doi.org/10.1016/j.jpcs.2018.08.009
Kang, S. Y., Zheng, Y. J., Van, K. T., Kim, Y. D., Pawar, A. U. and Pham, Q. L., Formation of a CdO layer on CdS/ZnO nanorod arrays to enhance their photoelectrochemical performance, ChemSusChem., 7(12), 3505-3512 (2014).
https://doi.org/10.1002/cssc.201402365
Kania, A., Szindler, M. M., Szindler, M., Brytan, Z. and Łoński, W., Structure and Selected Properties of SnO2 Thin Films, Mater., 17(13), 3348 (2024).
https://www.mdpi.com/1996-1944/17/13/3348
Kasap, O. S., Tan, C. W., Singh, J. and Ray, K. A., Fundamental Optical Properties of Materials I, Optical Properties of Materials and Their Applications, 2nd Ed., John Wiley & Sons Ltd, 1-36 (2020).
https://doi.org/10.1002/9781119506003.ch1
Khoshkhoo, S. M., Scudino, S., Thomas, J., Gemming, T., Wendrock, H. and Eckert, J., Size evaluation of nanostructured materials, Mater. Lett., 108, 343-345 (2013).
https://doi.org/10.1016/j.matlet.2013.06.035.
Kim, J. H., Yoo, M. S., Yu, S. and Lee, I. W., Photocatalytic Behavior of TiO2 Films: Thickness and Roughness Dependence, Rapid Commun. Photosci., 2(1), 1-8 (2013).
https://doi.org/10.5857/RCP.2013.2.1.001
Kite, V. S., Sathe, J. D., Patil, S. S., Bhosale, N. P. and Garadkar, M. K., Nanostructured TiO2 thin films by chemical bath deposition method for high photoelectrochemical performance, Mater. Res. Express, 6, 026411 (2018).
https://doi.org/10.1088/2053-1591/aaed81
Kumar, P. and Rao, K. G., The effect of precursor concentration and post-deposition annealing on the optical and micro-structural properties of SILAR deposited SnO2 films, Mater. Res. Express, 7(1), 016428 (2020).
https://doi.org/10.1088/2053-1591/ab6932
Kumar, S. and Tiwary, P. K., ZnCdS Thin Film: Preparation, Properties and Applications, Emerging Trends in Nanotechnology, Springer, Singapore185-219 (2021).
https://doi.org/10.1007/978-981-15-9904-0_7
Kumar, S., Rajpal, S., Sharma, K. S., Roy, D. and Kumar, R. s., Effect of Zn concentration on the structural, morphological and optical properties of ternary ZnCdS nanocrystalline thin films, Dig. J. Nanomater. Biostruct., 12(2), 339-347 (2017).
Laatar, F., Moussa, H., Alem, H., Balan, L., Girot, E., Medjahdi, G., Ezzaouia, H. and Schneider, R., CdSe nanorod/TiO2 nanoparticle heterojunctions with enhanced solar- and visible-light photocatalytic activity, Beilstein J. Nanotechnol., 8, 2741-2752 (2017).
https://doi.org/10.3762/bjnano.8.273
Larbah, Y., Adnane, M. and Sahraoui, T., Effect of substrate temperature on structural and optical properties of spray deposited ZnO thin films, Mater. Sci.-Pol., 33(3), 491-496 (2016).
https://doi.org/10.1515/msp-2015-0062
Li, Q., Meng, H., Zhou, P., Zheng, Y., Wang, J., Yu, J., and Gong, J., Zn1–xCdxS Solid Solutions with Controlled Bandgap and Enhanced Visible-Light Photocatalytic H2-Production Activity, ACS Catal., 3(5), 882-889 (2013).
https://doi.org/10.1021/cs4000975.
Ling, M., Taylor, A., Thakur, K. P., Scanlon, O. D., Parkin, P. I.,Vazquez, S. C., Durrant, R. J., Kafizas, A., Blackman, S. C., Cabrera, Q. R., Palgrave, G. R., Lee, L. T. and Watson, W. G., Evidence and Effect of Photogenerated Charge Transfer for Enhanced Photocatalysis in WO3/TiO2 Heterojunction Films: A Computational and Experimental Study, Adv. Funct. Mater., 27(18), 1605413 (2017).
https://doi.org/10.1002/adfm.201605413.
Mandal, R., Pramanik, S., Kuiri, K. P., Mukherjee, B. and Nath, R., Synergistic effect of grain size and surface oxygen vacancies for enhanced photoresponse properties of nanocrystalline SnO2 films, Opt. Mater., 155, 115917 (2024).
https://doi.org/10.1016/j.optmat.2024.115917
Manole, A. V., Dobromir, M., Gîrtan, M., Mallet, R., Rusu, G. and Luca, D., Optical properties of Nb-doped TiO2 thin films prepared by sol–gel method, Ceram. Int., 39(5), 4771-4776 (2013).
https://doi.org/10.1016/j.ceramint.2012.11.066
Mathews, R. N., Morales, R. E., Jacome, C. A. M. and Antonio, T. A. J., TiO2 thin films – Influence of annealing temperature on structural, optical and photocatalytic properties, Sol. Energy, 83(9), 1499-1508 (2009).
https://doi.org/10.1016/j.solener.2009.04.008.
Mazumder, K., Voit, B. and Banerjee, S., Recent Progress in Sulfur-Containing High Refractive Index Polymers for Optical Applications, ACS Omega, 9(6), 6253-6279 (2024).
https://doi.org/10.1021/acsomega.3c08571
Minami, T., Transparent conducting oxide semiconductors for transparent electrodes, Semicond. Sci. Technol., 20(4), S35 (2005).
https://doi.org/10.1088/0268-1242/20/4/004
Mittal, A., Kumar, N., Sharma, S. and Chauhan, N. S., TiO2 and its composites as promising biomaterials: a review, BioMetals, 31, 147-159 (2018).
https://doi.org/10.1007/s10534-018-0078-6
Monshi, A., Foroughi, R. M. and Monshi, R. M., Modified Scherrer Equation to Estimate More Accurately Nano-Crystallite Size Using XRD, World J. Nano Sci. Eng., 2(3), 154-160 (2012).
https://doi.org/10.4236/WJNSE.2012.23020
Mukherjee, A., Fu, M. and Mitra, P., Influence of Zn incorporation in CdS: Structural and morphological studies, J. Phys. Chem. Solids, 82, 50-55 (2015).
https://doi.org/10.1016/j.jpcs.2015.03.009
Naujokaitis, A., Savickaja, I., Juodkazytė, J., Grigucevičienė, A., Pakštas, V. and Šebeka, B., Study on charge transfer processes in thin-film heterojunction between cuprous oxide and hematite, Mater. Sci. Semicond. Process., 80, 56-62 (2018).
https://doi.org/10.1016/j.mssp.2018.02.020
Nguyen, T. T., Patel, M., Kim, W. J., Lee, W. and Kim, J., Functional TiO2 interlayer for all-transparent metal-oxide photovoltaics, J. Alloys Compd., 816, 152602 (2020).
https://doi.org/10.1016/j.jallcom.2019.152602
O'Regan, B. and Grätzel, M., A low-cost, high-efficiency solar cell based on dye-sensitized colloidal TiO2 films, Nat., 353, 737-740, (1991).
https://doi.org/10.1038/353737a0
Özçelik, V. O., Azadani, J. G., Yang, C., Koester, J. S. and Low, T., Band alignment of two-dimensional semiconductors for designing heterostructures with momentum space matching, Phys. Rev. B, 94(3), 035125 (2016).
https://doi.org/10.1103/PhysRevB.94.035125
Palma, M. J. R., Duart, M. M. J. and Macleod, A., Determination of the optical constants of a semiconductor thin film employing the matrix method, IEEE Trans. Educ., 43(1), 63-68, (2000).
https://doi.org/10.1109/13.825742
Podelinska, A., Neilande, E., Pankratova, V., Serga, V., Bandarenka, H., Burko, A., Piskunov, S., Pankratov, V. A., Sarakovskis, A., Popov, I. A. and Bocharov V. D., Structural and Spectroscopic Characterization of TiO2 Nanocrystalline Materials Synthesized by Different Methods, Nanomater., 15(7), 498 (2025).
https://www.mdpi.com/2079-4991/15/7/498
Pyun, I. S. and Kim, H. C., Determination of donor concentration in anodically passivating polycrystalline TiO2 films from analysis of nonlinear Mott-Schottky plots, Int. J. Hydrogen Energy, 16, 661-664 (1991).
https://doi.org/10.1016/0360-3199(91)90187-N
R. Shashidhar, R., and L. C. S. Murthy. "Influence of thickness and air annealing on structural, morphological, compositional, electrical properties of sprayed TiO^ sub 2^ thin films." International Journal of Engineering Science and Technology 5.4 (2013): 747.
Saad, F. O., Nadir, F. H. and Sami, S. C., Physical characterization of sprayed SnO2 thin films, Mater. Sci.: an Indian J., 10(9), 397-401 (2014).
Schneider, J., Matsuoka, M., Takeuchi, M., Zhang, J., Horiuchi, Y., Anpo, M. and Bahnemann, W. D., Understanding TiO2 Photocatalysis: Mechanisms and Materials, Chem. Rev., 114(19), 9919-9986 (2014).
https://doi.org/10.1021/cr5001892
Selvakumari, C. J., Ahila, M., Malligavathy, M. and Padiyan, P. D., Structural, morphological, and optical properties of tin(IV) oxide nanoparticles synthesized using Camellia sinensis extract: a green approach, Int. J. Miner., Metall. Mater., 24, 1043-1051 (2017).
https://doi.org/10.1007/s12613-017-1494-2
Serin, T., Serin, N., Karadeniz, S., Sarı, H., Tuğluoğlu, N. and Pakma, O., Electrical, structural and optical properties of SnO2 thin films prepared by spray pyrolysis, J. Non·Cryst. Solids, 352(3), 209-215 (2006).
https://doi.org/10.1016/j.jnoncrysol.2005.11.031
Singh, N. V., Min, S. H., Jang, J. S. and Mahadik, M., Metal Oxide based Chalcogenides Heterostructure Thin Film Photoanodes for Photoelectrochemical Solar Hydrogen Generation, Asian J. Chem., 31(1), 18-24 (2019).
https://doi.org/10.14233/AJCHEM.2019.21647
Singh, N., Mehra, R. M., Kapoor, A. and Soga, T., ZnO based quantum dot sensitized solar cell using CdS quantum dots, J. Renewable Sustainable Energy, 4(1), 013110 (2012).
https://doi.org/10.1063/1.3683531
Štengl, V. and Králová, D., TiO2/ZnS/CdS Nanocomposite for Hydrogen Evolution and Orange II Dye Degradation, Int. J. Photoenergy, 2011(1), 532578 (2011).
https://doi.org/10.1155/2011/532578
Sun, J. R., Yan, W., Chang, W., Yang, R, G. and Ren, S. X., Effect of Calcination Temperature on Characterization and Photocatalytic Activity of Cd0.6Zn0.4S/TiO2 Hierarchical Heterostructure, Adv. Mater. Res., 1092-1093, 980-983 (2015).
https://doi.org/10.4028/www.scientific.net/AMR.1092-1093.980
Urper, O., Tonka, M. and Baydogan, N., Modification of optical constants at nanospherical ZnO:Al thin film, J. Mater. Sci.: Mater. Electron., 34(4), 1-11 (2023).
https://doi.org/10.1007/s10854-022-09751-z
Vadivel, S., Rajarajan, G. Influence of Cu doping on structural, optical and photocatalytic activity of SnO2 nanostructure thin films. J Mater Sci: Mater Electron 26, 5863–5870 (2015).
https://doi.org/10.1007/s10854-015-3154-5
Wei, L., Zeng, D., He, X., Wang, L., Bao, Y., He, G., Fujita, T. and Ong, J. W., Tunable Bandgap Engineering of Zn x Cd1−x Se Solid Solution with Controlled Ratio via a Facile One-Pot Synthesis for Visible-Light Photocatalytic H2 Production, Adv. Energy Sustainability Res., 3(5), 2100210 (2022).
https://doi.org/10.1002/aesr.202100210
Wu, H., Yuan, C., Chen, R., Wang, J., Dong, F., Li, J. and Sun, Y., Mechanisms of Interfacial Charge Transfer and Photocatalytic NO Oxidation on BiOBr/SnO2 p–n Heterojunctions, ACS Appl. Mater. Interfaces, 12(39), 43741-43749 (2020).
https://doi.org/10.1021/acsami.0c12628
Y. B. Bendahmane, N. E. H. Touidjen and F. Mansour, "Characterization of SnO2 Thin Films Fabricated by Chemical Spray Pyrolysis," 2019 International Conference on Advanced Electrical Engineering (ICAEE), Algiers, Algeria, 2019, pp. 1-6, doi: 10.1109/ICAEE47123.2019.9015158.
Kaawash, N.M.S., Halge, D.I., Narwade, V.N., Thabit, M.Y.H., Khanzode, P.M., Dadge, J.W., Alegaonkar, P.S. and Bogle, K.A. (2024), Nitrocellulose-Passivated SnO2 Thin Film as a Ultraviolet-C Photodetector. Adv. Eng. Mater., 26: 2301602.
https://doi.org/10.1002/adem.202301602
Yang, W., Xu, Y., Bu, Q., Zhao, R., Xu, W., Jia, N. and Yu, G., 0D/1D type Ⅱ CdS/TiO2 nanocone arrays/Ti hybrids for visible-light-driven rapid photocatalytic degradation of tetracycline: An insight investigation of the interfacial electron transport mechanism, Appl. Surf. Sci., 643, 158688 (2024).
https://doi.org/10.1016/j.apsusc.2023.158688.
Yang, Y., Wang, Y. and Yin, S., Oxygen vacancies confined in SnO2 nanoparticles for desirable electronic structure and enhanced visible light photocatalytic activity, Appl. Surf. Sci., 420, 399-406 (2017).
https://doi.org/10.1016/j.apsusc.2017.05.176
Yusuf, S. A., Abubakar, A. A., Mohammed, K. I., Ahmadu, U. and Isah, U. K., A review of coating tin oxide electron transport layer for optimizing the performance of perovskite solar cells, Chem. Inorg. Mater., 6, 100100 (2025).
https://doi.org/10.1016/j.cinorg.2025.100100
Zulfiqar, S., Khan, R., Yuan, Y., Iqbal, Z., Yang, J., Wang, W., Ye, Z. and Jianguo, L., Variation of structural, optical, dielectric and magnetic properties of SnO2 nanoparticles, J. Mater. Sci.: Mater. Electron., 28, 4625-4636 (2017).
