Dr. Abdelhafed Taleb

(Dr. Abdelhafed Taleb, Chimie ParisTech, Pierre & Marie Curie University, Paris, France)
Over the last decade, the photovoltaic energy appears as a potential alternative to the currently dominant fossil energy. Furthermore, despite the great scientific and technical advances made in photovoltaic solar cell, significant challenges remain for the design and synthesis of novel material architectures that must be low-cost and have high energy conversion efficiency. Design of new material architecture has emerged as an interesting aspect of nanotechnology for fabricating advanced multifunctional materials. In fact, to obtain materials with the desired properties, chemical composition is not enough and the geometrical aspect has to be considered. Beyond nanostructuring of material with uniform composition, design of hybrid nanocomposites is an alternative approach to create a synergy between different components which will enhance the existing properties or induce new properties. However, optimization of material properties becomes a balancing act in which several parameters must be taken into account: chemical composition and material structure [1]. 

To optimize the overall solar energy conversion efficiency, it is important to determine material architecture of prepared nanocomposite films that lower recombination currents and enhance light absorption and harvesting. Improving the efficiency of photo-induced charge separation and transport remains a challenge. The photosensitization with visible and IR light absorbing dyes has led to development of dye-sensitized solar cells (DSSC) with efficiencies greater than 10% [2]. Furthermore, the increase in TiO2 film thickness results in higher light harvesting but promotes charge recombination and consequently a further limitation of charge transport through the film which in turn reduces the solar energy conversion efficiency. Since the emergence of the concept of DSSCs by O’Reagan and Grätzel in 1991 [1], there has been a proliferation of design methods to form TiO2 film with optimized architecture. Recently it was shown that a multi-scale structure of TiO2 film composed of micron sized particles with high specific surface area, such as mesoporous TiO2 beads [3], nano-embossed hollow spherical TiO2 particles [4], exhibits many advantages, large surface area for dye molecules adsorption and light harvesting efficiency, which improve DSSC performances.

In the present work, we report different strategies to control TiO2 anatase nanoparticles packing and film architectures. Efficiency of DSSC fabricated with the obtained TiO2 packing aggregate films was reported to depend on the size of the packing aggregate and the film architecture. We show that the increasing of the TiO2 aggregate size (number of TiO2 nanoparticles) improves DSSC performances [5]. The obtained results were discussed in terms of a balance between the incident light scatterings, dye adsorption, cracks free structure and the efficiency of electron transfer (reduction of recombination process).

References:
[1] O’Reagan and Grätzel, Nature, 353 (1991) 737.
[2] S. K. Deb, Solar Energy Materials &solar cells, 88 (2005) 1.
[3] F. Huang, D. Chen, X. L. Zhang, R. A. Caruso, Y. B. Cheng, Advanced Functional Materials 20 (2010) 1301
[4] H. J. Koo, Y. J. Kim,; Y. H. Lee, W. I. Lee, K. Kim, N. G. Park, Advanced Materials 20 (2008) 195
[5] A. Taleb, F. Mesguich, X. Yanpeng, C. Colbeau-Justin, P. Dubot, submitted (2014)

Biography of Dr. Abdelhafed Taleb:

Abdelhafed Taleb is associate professor at University of Pierre & Marie Curie in the “Institut de recherche de Chimie Paris” (IRCP / ENSCP), where he is leading the group “Elaboration and Modelling of Nanostructred Films” group. He received his PhD diploma in nanomaterials science under the supervision of Prof. Marie Paul Pileni from University Pierre & Marie Curie in Paris in 1998. During his PhD, he pointed out a new collective’s properties due to nanoparticles organisation. In 2000, he joined the UPMC, where he worked on the synthesis of inorganic-organic hybrid nanomaterials and the development of new strategies to assemble them in different structures. In 2005, he joined Jean Pierre Badiali’s group where he focused on the corrosion process simulation as a new way to prepare nanomaterials. Since 2009, he leads the group focusing on the design of nanostructured films with novel properties and their applications in different areas such as sensing, self-cleaning coating, photovoltaic (DSSC), anticorrosion coating, magnetic storage etc …