Fundamental understanding of charge transfer and transport at the nanoscale is important across disciplines as diverse as biology, chemistry, physics and engineering. In one hand, nanoscale objects are defined by large area-to-volume ratios, hence surface chemistry play a pivotal role on sample's functionality; furthermore, quantum confinement of charge carriers at the nanoscale make object's optoelectronic properties to be strongly tunable with structure. In this respect, establishing neat correlations between surface chemistry, structure and charge carrier dynamics taking place in nanostructured hybrid systems represent one of the most significant leading contemporary topics in applied physics, physical chemistry and material science.

Interfacial charge carrier dynamics in sensitized oxides

The sensitization of mesostructured oxides by excitonic absorbers (e.g. quantun dots or molecular dyes) represent an appealing route for developing low cost photovoltaic and photocatalytic devices.

We are interested on the analysis, modeling and ultimately fine-tuning of interfacial carrier dynamics in sensitized oxides with the aim of boosting photocovertion efficieny in solar energy conversion schemes (solar cells and fuels).

Dipolar Molecular Capping in Quantum Dot-Sensitized Oxides: Fermi Level Pinning Precludes Tuning Donor-Acceptor Energetics

Hai I. Wang, Hao Lu, Yuki Nagata, Mischa Bonn and Enrique Cánovas*, ACS Nano 11(5), 4760 (2017).

Boosting power conversion efficiencies of quantum-dot-sensitized solar cells beyond 8% by recombination control

Ke Zhao, Zhenxiao Pan, Ivan Mora-Sero, Enrique Canovas, Hai Wang, Ya Song, Xueqing Gong, Jin Wang, Mischa Bonn, Juan Bisquert, Xinhua Zhong, Journal of the American Chemical Society 137 (16), 5602-5609 (2015).

Interplay between structure, stoichiometry and electron transfer dynamics in SILAR-based quantum dot-sensitized oxides

H. Wang, I. Barceló, T. Lana-Villareal, R. Gómez, M. Bonn and E. Cánovas*, Nano Letters, 14(10), 5780-5786 (2014).

Tuning electron transfer rates through molecular bridges in quantum dot sensitized oxides

H. Wang, E. R. McNellis, S. Kinge, M. Bonn and E. Cánovas*, Nano Letters, 13(11), 5311-5315 (2013).

Size-Dependent Electron Transfer from PbSe Quantum Dots to SnO2 Monitored by Picosecond Terahertz Spectroscopy

E. Cánovas*, P. Moll, S. A. Jensen, Y. Gao, A. J. Houtepen, L. D. A. Siebbeles, S. Kinge and M. Bonn, Nano Letters 11, 5234 (2011).

Charge transport in nano- micro-structured hybrid systems

We are actively interrogating transport in nano- and micro-structured hybrid systems. THz spectroscopy is unique tool to characterize the nature of the photoconductivity with sub-ps resolution and in a contactless fashion. This is due to the fact that, in contrast to other pump-probe techniques, THz spectroscopy allows for the identification and modelling of the photo-generated species (e.g. excitons vs free carriers) via the frequency resolved complex conductivity.

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Phonon–electron scattering limits free charge mobility in methylammonium lead iodide perovskites

M Karakus, SA Jensen, F D’Angelo, D Turchinovich, M Bonn, E Canovas*, The journal of physical chemistry letters 6 (24), 4991-4996 (2015).

3rd generation photovoltaics

A conventional solar absorber suffers from two intrinsic major energy loss channels: (1) its inability to absorb photons with energy less than the material absorption threshold and (2) the waste of photon energy when photons with energies above the absorption threshold are absorbed (cooling). These aspects set a 30% upper efficiency limit for single gap photoconverters (the Shockley-Queisser limit). Part of our research efforts are focused on identifying and engineering nanostructured systems for diminishing those energetic losses towards breaking the 30% photoconversion efficiency barrier.

Efficient Hot Electron Transfer in Quantum Dot-Sensitized Mesoporous Oxides at Room Temperature

HI Wang*, I Infante, S Brinck, E Cánovas*, M Bonn*, Nano letters 18 (8), 5111-5115 (2018).

Boosting Biexciton Collection Efficiency at Quantum Dot-Oxide Interfaces by Hole Localization at the Quantum Dot Shell

Hai Wang, Mischa Bonn and Enrique Cánovas*, The Journal of Physical Chemistry Letters 8(12), 2654 (2017).

Molecular (opto)electronics

The field of molecular electronics analyses new paradigms for electronic devices approaching closer towards the limits of miniaturisation and aim exploring additional functionality to current device platforms by exploiting novel phenomena at the nanoscale (“More than Moore”).

In our group, we are interested on estimating the conductance of single molecules by measuring ET rates through well-defined donor-molecular bridge-acceptor assembles.

Tuning electron transfer rates through molecular bridges in quantum dot sensitized oxides

H. Wang, E. R. McNellis, S. Kinge, M. Bonn and E. Cánovas*, Nano Letters, 13(11), 5311-5315 (2013).

Nanostructured Photovoltaics

Max Planck Partner Group