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Neuartige mesoporöse Filme transparenter Oxide für optoelektronische Anwendungen mit optimierten Eigenschaften

Fachliche Zuordnung Physikalische Chemie von Festkörpern und Oberflächen, Materialcharakterisierung
Förderung Förderung von 2012 bis 2017
Projektkennung Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 222760133
 
Erstellungsjahr 2018

Zusammenfassung der Projektergebnisse

The project was aimed at the development of nanostructured transparent conducting oxides (TCOs) for their use as advanced current collectors for electrochemical applications. Nanostructured TCO layers gain increasing importance as a novel type of electrodes for optoelectrochemical devices due to a combination of a high surface area with a large conducting interface and optical transparency. The availability of such electrodes have been however limited so far because of numerous synthetic challenges, which have been successfully addressed in this project. We have developed a new synthesis of antimony-doped tin oxide (ATO) resulting in very small nanoparticles with a size below 3 nm. The nanoparticles feature high electrical conductivity, which increases by several orders of magnitude upon substitutional doping with antimony, and are very good dispersible in polar solvents such as water and ethanol that was not achieved before. In collaboration with Dr. H. Nemec (Institute of Physics, Prague) we have investigated the particle conductivity using terahertz spectroscopy. It was shown that the conductivity increase upon doping is caused by the transition from hopping in the undoped samples to band-like conduction in the doped samples. Significant part of our research was devoted to the assembly of nanoparticles to nanostructured TCO electrode layers with a special focus on the control of pore morphology. We have investigated different template-assisted self-assembly strategies to obtain 3D-electrode morphologies with targeted pore size and adjustable performance. Particularly notable in this respect was the use of a novel PEO-b-PHA block copolymer performed in collaboration with Prof. M. Stefik, which enabled tunable ATO morphologies with adjustable pore sizes from 10 nm mesopores to 80 nm macropores by changing the solution processing conditions. The importance of the morphology control was demonstrated by us on an example of differently sized electroactive species adsorbed on the electrode surface. While all the obtained electrodes incorporated a large amount of small redox molecules, only the electrodes with larger macropores were able to accommodate high amounts of bulky photoactive photosystem I (PSI) protein complexes. Remarkable also is an 11-fold enhancement of the current response of PSI modified macroporous ATO electrodes compared to the planar TCOs, which makes the developed ATO layers promising electrodes for biohybrid electrochemical devices. We have also developed the procedure to fabricate macroporous TCO electrodes using shape-persistent latex (PMMA) beads as the porosity templates. We have applied this procedure to produce macroporous ATO films with 300 nm large pores. Furthermore, we used this approach to fabricate tin doped indium oxide (ITO) macroporous electrodes from waterdispersible indium tin hydroxide nanoparticles developed by us in the first project, resulting in conducting macroporous ITO films with a large periodically ordered conducting interface. An important objective of our project was the use of developed TCO layers as advanced current collectors for electrochemical applications. As a part of this study we have investigated the interaction of TCO nanostructures with different redox molecules such as photosystem- and small redox proteins enabling their efficient incorporation and resulting in a greatly increased electrochemical response. These impressive results, published by us in several papers and presented on numerous conferences, have attracted attention of different research groups and initiated collaborative projects on novel applications. Thus, together with Prof. F. Lisdat (TU Wildau) we have used porous TCO electrodes to develop enzyme-based biosensors. We have fabricated hybrid electrodes on the base of macroporous ITO layers containing polymerentrapped enzymes (pyrroloquinoline quinone-dependent glucose dehydrogenase, fructose dehydrogenase and xanthine dehydrogenase). The use of macroporous instead of planar ITO electrodes resulted in a significantly enhanced bioelectrocatalysis and an increased stability of the devices. Together with A. Hufnagel and Prof. T. Bein (LMU) we have demonstrated that the use of nanostructured TCO current collectors instead of conventional planar electrodes can significantly improve the performance of photoelectrodes for water splitting. Atomic layer deposition of thin zinc ferrite photoabsorber layers on macroporous ATO electrodes increased the photocurrent up to five times compared to the planar electrodes.

Projektbezogene Publikationen (Auswahl)

 
 

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