Terahertz time-domain spectroscopy; Complex conductivity; Hole-transporting materials; Organic electronics; Ultrafast laser spectroscopy; Electron transfer dynamics; Charge carrier dynamics; Charge transport
Thorsmølle Verner K., Topgaard Daniel, Brauer Jan C., Zakeeruddin Shaik M., Grätzel Michael, Moser Jacques-E. (2012), Conduction through Viscoelastic Phase in a Redox-Active Ionic Liquid at Reduced Temperatures, in Advanced Materials
, 24, 781-784.
Paracchino Adriana, Brauer Jan Cornelius, Moser Jacques-Edouard, Thimsen Elijah, Grätzel Michael (2012), Synthesis and characterization of high-photoactivity electrodeposited Cu2O solar absorber by photoelectrochemistry and ultrafast spectroscopy, in J. Phys. Chem. C
, 116, 7341-7350.
Thorsmølle Verner K., Brauer Jan Cornelius, Zakeeruddin Shaik M., Grätzel Michael, Moser Jacques-E. (2012), Temperature-dependent ordering phenomena of a polyiodide system in a redox-active ionic liquid, in J. Phys. Chem. C
, 116, 7989-7992.
Thorsmolle VK, Rothenberger G, Topgaard D, Brauer JC, Kuang DB, Zakeeruddin SM, Lindman B, Gratzel M, Moser JE (2011), Extraordinarily Efficient Conduction in a Redox-Active Ionic Liquid, in CHEMPHYSCHEM
, 12(1), 145-149.
Punzi A, Brauer JC, Marchioro A, Ghadiri E, de Jonghe J, Moser JE (2011), Photoinduced Interfacial Electron Transfer and Lateral Charge Transport in Molecular Donor-Acceptor Photovoltaic Systems, in CHIMIA
, 65(5), 353-355.
Brauer Jan C., Teuscher Joël, Punzi Angela, Moser Jacques-E. (2011), Transient photoconductivity of dye-sensitized TiO2 nanocrystalline films probed by optical pump-THz probe spectroscopy, in Chergui M. (ed.), Oxford University Press, New York, 358-360.
The conducting and semiconducting properties of organic charge-transport materials, and hybrid inorganic-organic distributed heterojunction systems have attracted considerable attention over the past decade due to several important applications in unconventional photoactive systems and organic electronics, such as light emitting diodes and photovoltaic cells. A systematic technique to accurately measure the charge transport parameters, and to understand the carrier dynamics in these disordered systems is yet to be fully developed. Terahertz time-domain spectroscopy (THz-TDS) is a very powerful technique for material studies, which covers the spectral range ~ 0.2-10 meV, bridging the gap between microwave and infrared experimental methods. Linear THz-TDS as a contact less, coherent optical technique allows for direct determination of the complex conductivity of materials. Both the absorption and the dispersion of the sample can be measured directly, allowing in particular to discriminate between free charge carrier and excitonic transport. Optical-pump THz-probe spectroscopy (OPTP) is a powerful tool to temporally resolve phenomena at the fundamental timescales of nuclear and electronic motion. This method probes charge transport over nano-scale distances, allowing for the determination of the intrinsic mobility of charge carriers in a material.The objective of the present project is to use THz spectrometry for ultrafast time-resolved conductivity studies of various materials as a function of frequency, temperature and pressure. We will utilize THz-TDS and OPTP spectroscopies to study photogenerated charge carriers transport and dynamics in nanocrystalline inorganic, organic charge transport materials and nanocomposite hybrid systems. Redox-active ionic liquids, hole transporting molecular liquids, such as alkoxylated triarylamines, amorphous solid hole-conducting materials, such as spiro-MeOTAD, cyanine dye and DPP layers will be more particularly scrutinized. The effect of the crystallinity of the materials upon the mobility and trapping of charge carriers, as well as the influence of nanostructuring will be in the focus of this research. Charge transport in oxide nanoparticle networks of importance for dye-sensitized photovoltaic solar cells will be studied in the absence and in the presence of organic hole transporting materials filling the pores. Important results regarding the correlation of electron and holes on both sides of the distributed interface are expected to be gained through the use of THz spectroscopy.Finally, low frequency vibrations that are associated with the self trapping of charges in small polarons can as well be observed in the frequency range 0.2 - 4 THz. Application of OPTP spectroscopy will thus provide invaluable information on the detailed mechanism of interfacial light-induced electron transfer and charge transport processes in dye-sensitized photoactive hybrid devices.