Proceedings of 6th International Conference on Hybrid and Organic Photovoltaics (HOPV14)
Publication date: 1st March 2014
We report electron transfer (ET) rates in dye sensitized oxide systems as a function of donor-acceptor Gibbs free energy difference (ΔG, i.e. ET driving force) using high-frequency (TeraHertz) conductivity measurements.A set of 3 Ru based dyes (RuN3, Ru505 and Ru470) sensitizing SnO2 matrices were studied. These samples are defined by decreasing donor-acceptor ET driving forces (ΔG(RuN3) > ΔG(Ru505) > ΔG(Ru470), see figure 1/left) and were selected for their identical donor-acceptor coupling strengths due to identical bonding geometry and LUMO localization – as supported by DFT calculations.
Optical pump-THz probe spectroscopy (OPTP), allowing for ultrafast, contact-free conductivity measurements, is uniquely suited for investigation of electron transfer (ET) rates in sensitized architectures.1-4 While charge carriers are confined within the molecular dyes (lack of ET), no real conductivity would be measurable in the system. When ET occurs after dye photo-excitation, the THz probe will interact with free electrons populating the oxide, giving rise to a time-dependent photo-conductivity signal which is directly proportional to the product of electron density and mobility within the mesoporous oxide. The time-dependent increase in conductivity (inset in fig. 1) directly provides the ET rate. For the studied systems, Marcus theory predicts slower ET rates for reduced ΔG(Ket(RuN3) > Ket(Ru505) > Ket(Ru470)). However, as seen in Figure 1/left we observed identical rates for the Ru505 and Ru470 dyes. This observation points to an enhanced donor-acceptor wave-function overlap (coupling strength) for the Ru470 dye compared with Ru505.
With the help of first principles calculations (see figure 1/right) we show that the ET from the ionic Ru470 dye to the SnO2 oxide is only energetically feasible if the dye is neutralized after bonding, i.e. 2 electrons are donated from the oxide. The strong resulting dipole at the dye/oxide interface is likely responsible for the enhanced ET for the ionic Ru470 dye when compared with the neutral Ru505.
Figure 1. left) OPTP dynamics (inset) and ET rates of dyes RuN3, Ru505 and Ru470 sensitizing SnO2. Right) DFT calculations for total energies (G for T=0K) of Ru505, ionic Ru470 (in solution) and neutralized Ru470 (adsorbed).
1-Pijpers, J. J. H. ; Koole, R. ; Evers, W. H.; Houtepen, A. J.; Boehme, S.; Donegá, C. d. M.; Vanmaekelbergh, D.; Bonn, M. Spectroscopic Studies of Electron Injection in Quantum Dot Sensitized Mesoporous Oxide Films. Phys. Chem. C 2010, 114, 18866–18873. 2- Pijpers, J. J. H.; Koole, R.; Evers, W. H.; Houtepen, A. J.; Boehme, S.; Donegá, C. d. M.; Vanmaekelbergh, D.;Bonn, M. Picosecond Electron Injection Dynamics in Dye-Sensitized Oxides in the Presence of Electrolyte. J. Phys. Chem. C 2011, 115, 2578, 2578–2584. 3-Cánovas, E.; Moll, P.; Jensen, S. A.; Gao, Y.; Houtepen, A. J.; Siebbeles, L. D. A.; Kinge, S.; Bonn, M. Size-Dependent Electron Transfer from PbSe Quantum Dots to SnO2 Monitored by Picosecond Terahertz Spectroscopy. Nano Letters 2011, 11, 5234–5239. 4- Wang, H.; McNellis, E. R.; Kinge, S.; Bonn, M.; Cánovas, E. Tuning Electron Transfer Rates through Molecular Bridges in Quantum Dot Sensitized Oxides. Nano letters 2013, 13, 5311–5315.
nanoGe is a prestigious brand of successful science conferences that are developed along the year in different areas of the world since 2009. Our worldwide conferences cover cutting-edge materials topics like perovskite solar cells, photovoltaics, optoelectronics, solar fuel conversion, surface science, catalysis and two-dimensional materials, among many others.
Previously nanoGe Spring Meeting (NSM) and nanoGe Fall Meeting (NFM), MATSUS is a multiple symposia conference focused on a broad set of topics of advanced materials preparation, their fundamental properties, and their applications, in fields such as renewable energy, photovoltaics, lighting, semiconductor quantum dots, 2-D materials synthesis, charge carriers dynamics, microscopy and spectroscopy semiconductors fundamentals, etc.
International Conference on Hybrid and Organic Photovoltaics
International Conference on Hybrid and Organic Photovoltaics (HOPV) is celebrated yearly in May. The main topics are the development, function and modeling of materials and devices for hybrid and organic solar cells. The field is now dominated by perovskite solar cells but also other hybrid technologies, as organic solar cells, quantum dot solar cells, and dye-sensitized solar cells and their integration into devices for photoelectrochemical solar fuel production.
Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics
The main topics of the Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics (IPEROP) are discussed every year in Asia-Pacific for gathering the recent advances in the fields of material preparation, modeling and fabrication of perovskite and hybrid and organic materials. Photovoltaic devices are analyzed from fundamental physics and materials properties to a broad set of applications. The conference also covers the developments of perovskite optoelectronics, including light-emitting diodes, lasers, optical devices, nanophotonics, nonlinear optical properties, colloidal nanostructures, photophysics and light-matter coupling.
The International Conference on Perovskite Thin Film Photovoltaics Perovskite Photonics and Optoelectronics (NIPHO) is the best place to hear the latest developments in perovskite solar cells as well as on recent advances in the fields of perovskite light-emitting diodes, lasers, optical devices, nanophotonics, nonlinear optical properties, colloidal nanostructures, photophysics and light-matter coupling.