Performance of TiO₂ Aggregates-Based Dye Solar Cells

Abstract:

TiO2 aggregates-based dye solar cells (DSCs) have gained an increasing interest due to their better light harvesting efficiency as a result of enhanced light scattering effect from the submicron spherical aggregates that can generate more electrons and the high internal surface area for dye chemisorption provided by nanocrystallites which made up the aggregates. Optimized TiO2 aggregates (0.45 µm) composing of nanocrystallites (10-40 nm) with desired physicochemical properties for enhanced overall light conversion efficiency of DSC were synthesized by varying the calcination temperature and water content in the hydrolysis of titanium alkoxide in ethanol. TiO2 aggregates obtained were characterized using FESEM, XRD and UV-Vis spectroscopy. The assembled DSCs were then evaluated using solar simulator under AM 1.5 (100 mW/cm2) simulated sunlight. Nanocrystallites were found to have an increasing size of 12 nm to 36 nm with increasing calcination temperature of 400C to 600C. Sample of aggregates calcined at 500C recorded the highest efficiency (4.456%) as the 20-nm nanocrystallites produced is considered to be the optimum size for dye absorption. With higher water content in the hydrolysis process, the aggregates lose their spherical shapes resulting in lower absorption intensity indicating the occurrence of low light scattering in the TiO2 film. Highest conversion efficiency was observed for DSC that used well-defined spherical TiO2 aggregates composing of 20-nm nanocrystallites which were synthesized using ethanol with low water content (0.9 vol%) followed by calcination at 500C. Thus, optimized TiO2 nanocrystallites which form spherical aggregate is critical in order to improve light harvesting efficiency of DSCs.

• Periodical: Materials Science Forum (Volume 737)
• Pages: 137-144
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.737.137
• Online since: January 2013
• Authors: Norani Muti Mohamed, Siti Nur Azella Zaine
• Keywords: Aggregates, Calcination, Chemisorption, Efficiency, Nanocrystallites, Scattering

References

[1] M. Gratzel, Mesoporous oxide junctions and nanostructured solar cells, Current Opinion in Colloid & Interface Science 4 (1999) 314.

DOI: 10.1016/s1359-0294(99)90013-4

[2] S. Nakade, Y. Saito, W. Kubo, T. Kitamura, Y. Wada, S. Yanagida, Influence of TiO2 nanoparticle size on electron diffusion and recombination in dye sensitized TiO2 solar cells, J. Phys. Chem. B 107 (2003) 8607.

DOI: 10.1021/jp034773w

[3] X. Chen, S.S. Mao, Synthesis of titanium dioxide (TiO2) nanomaterial, J. Nanoscience & Nanotechnology 6 (2006) 906.

[4] J. Jiu, S. Isoda, M. Adachi, F. Wang, Preparation of TiO2 nanocrystalline with 3-5 nm and application for dye-sensitized solar cell, Journal of Photochemmistry and Photobiology A: Chemistry 189 (2007) 314.

DOI: 10.1016/j.jphotochem.2007.02.021

[5] Q. F. Zhang, C.S. Dandeneau, X.Y. Zhou, G.Z. Cao, ZnO nanostructures for dye-sensitized solar cells, Adv. Mater 19 (2009) 4087.

DOI: 10.1002/adma.200803827

[6] J. Liu, G.Z. Cao, Z., Yang, D. Wang, D., Dubois, D., X. Zhou, X., G.L. Graff, L.R. Pederson, J.G. Zhang, Oriented nanostructures for energy conversion and storage, ChemSusChem 1 (2008) 676.

DOI: 10.1002/cssc.200800087

[7] T. P. Chou, Q.F. Zhang, G.E. Fryxell, G.Z. Cao, Hierarchically structured ZnO film for dye-sensitized solar cells with enhanced energy conversion efficiency, Adv. Mater 19 (2001) 2588.

DOI: 10.1002/adma.200602927

[8] Q. F. Zhang, T.P. Chou, B. Russo, S.A. Jenekhe, G.Z. Cao, Polydisperse aggregates of ZnO nanocrystallites: A method for energy-conversion-efficiency enhancement in dye-sensitized solar cells, Adv. Funct. Mater 18(2008) 1654.

DOI: 10.1002/adfm.200701073

[9] E. A. Barringer, H.K. Bowen, High-purity, monodisperse TiO2 powders by hydrolysis of titanium tetraethoxide: 1. Synthesis and physical properties, Langmuir 1 (1985) 414.

DOI: 10.1021/la00064a005

[10] E. A. Barringer, H.K. Bowen, High-purity, monodisperse TiO2 powders by hydrolysis of titanium tetraethoxide: 2. Aqueous Interfacial Electrochemistry and Dispersion Stability, Langmuir 1 (1985) 420.

DOI: 10.1021/la00064a006

[11] J. H. Jean, T.A. Ring, Nucleation and growth of monosized TiO2 powders from alcohol solution, Langmuir 2 (1986) 251.

DOI: 10.1021/la00068a025

[12] Y. Hu, H-L. Tsai, C.L. Huang, Phase transformation of precipitated nanoparticles, Material Science and Engineering A 344 (2003) 209.

[13] Y. Lee, J. Chae , M. Kang, Comparison of the photovoltaic efficiency on DSSC for nanometer sized TiO2 using a conventional sol-gel and solvothermal methods, J. Industrial & Engineering Chem. 16 (2010) 609.

DOI: 10.1016/j.jiec.2010.03.008

[14] G. Boschloo, T. Edvinsson and A. Hagfeldt, Dye-Sensitization Nanostructured ZnO Electrodes for Solar Cell Applications, in Nanostructured Materials for Solar Energy Conversion, T. Sogo, Elseveir, UK (2006) 227.

DOI: 10.1016/b978-044452844-5/50009-3

[15] Y. Lee, J. Chae, M. Kang, Comparison of the photovoltaic efficiency on DSSC for nanometer sized TiO2 using a conventional sol-gel and solvothermal methods, Journal of Industrial & Engineering Chemistry 16 (2010) 609.

DOI: 10.1016/j.jiec.2010.03.008

[16] Y. Leng, X-Ray diffraction method, in Material Characterization: Introduction to Microscopic and Spectroscopic Methods, Hong Kong: John Wiley & Sons (Asia) Pte. Ltd., 2008, p.45.

[17] Q. F. Zhang, T. P. Chou, B. Russo, S. A. Jenekhe, and G. Z. Cao, Aggregation of ZnO nanocrystallites for high conversion efficiency in dye-sensitized solar cells, Angew. Chem. Int. Ed. 47 (2008) 2402.

DOI: 10.1002/anie.200704919