When 3:30 PM - 5:00 PM Sep 20, 2013
Where 1670 Beyster Building
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Atomistic Modelling of Nanostructured Solar Cell Interfaces: The Steep Path to Rational Design

Feliciano Giustino
University of Oxford, Department of Materials

The terms “nanostructured solar cells” broadly refer to those bio-inspired photovoltaic devices where the processes of light absorption and charge transport take place in different materials. In this category we find dye-sensitized and semiconductor-sensitized solar cells, organic photovoltaics and hybrid organic-inorganic cells. Despite the overwhelming multitude of device architectures and materials combinations, nanostructured solar cells share a common denominator, namely that the energy conversion efficiency critically depends on the physical and chemical properties of one or more donor-acceptor interfaces. The atomic and electronic structures of donor-acceptor interfaces underpin key properties and phenomena such as the open circuit voltage, the rates for carrier injection and recombination, and the dynamics of exciton dissociation. Despite their importance as the true “engine” of nanostructured solar cells, surprisingly little is known about even the most common interfaces. Furthermore in many important cases it is still unclear why certain materials combinations work better than others. In this talk, by reviewing some prototypical case studies from the research carried out at Oxford during the past three years, I will try to provide a critical assessment of where we stand in the computational modelling of donor-acceptor interfaces for nanostructured solar cells. In particular I will touch upon transition-metal oxide interfaces found in hybrid and sensitized solar cells, eg the ZnO/P3HT and the TiO2/N3 interfaces. I will discuss how we can use first-principles calculations in combination with photoelectron spectroscopy and scanning tunneling microscopy in order to improve our understanding of the atomistic structure and the electronic properties of such interfaces; and how to use first-principles calculations for performing some rudimentary computational design. From the talk it will become apparent how solar cell interfaces are so complex that in order to make progress we need to systematically combine atomistic modelling with materials characterization at the nanoscale: along the way to rational design experiment and theory must walk hand in hand.

1. C. E. Patrick and F. Giustino, O-1s core-level shifts at the anatase TiO2(101)/N3 photovoltaic interface: signature of H-bonded supramolecular assembly. Phys. Rev. B. 84, 085330 (2010).

2. C. E. Patrick and F. Giustino, Structural and electronic properties of semiconductor-sensitized solar cells interfaces. Adv. Funct. Mater. 21, 4663 (2011).

3. C. E. Patrick and F. Giustino, GW quasiparticle band gaps of anatase TiO2 starting from DFT+U. J. Phys.: Condens. Matter. 24, 202201 (2012).

4. K. Noori and F. Giustino, Ideal energy-level alignment at the ZnO-P3HT photovoltaic interface, Adv. Func. Mater. 22, 5089 (2012).

5. M. R. Filip, C. E. Patrick, and F. Giustino, GW quasiparticle band structures of stibnite, antimonselite, bismuthinite, and guanajuatite Phys. Rev. B 87, 205125 (2013).

6. C. E. Patrick and F. Giustino, Quantitative analysis of valence photoemission spectra and quasiparticle excitations at chromophore-semiconductor interfaces, Phys. Rev. Lett. 109, 116801 (2012).

7. C. K. Yong, K. Noori, Q. Gao, H. J. Joyce, H. H. Tan, C. Jagadish, F. Giustino, M. B. Johnston, and L. M. Herz, Strong carrier lifetime enhancement in GaAs nanowires coated with semiconducting polymer, Nano Letters 12, 6293 (2012).

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