Dresden 2020 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 24: Functional semiconductors for renewable energy solutions I (joint session HL/CPP)

HL 24.6: Vortrag

Dienstag, 17. März 2020, 11:30–11:45, POT 151

Photoanode protection by atomic-layer-deposited TiO₂ thin films — •Oliver Bienek, David Silva, and Ian D. Sharp — Technische Universität München, Walter Schottky Institut, Germany

In the development of artificial photosystems, significant effort has been devoted to preventing the degradation of photoanodes under harsh electrochemical reaction environments. A promising solution is the deposition of highly conformal protective coatings by atomic layer deposition (ALD). While the application of TiO₂ protection layers to improve the stability of photoanodes has been demonstrated successfully, questions remain regarding the mechanisms of charge carrier transport across the interface and the critical role of defects on performance characteristics. In this work, TiO₂ thin films are fabricated by plasma-enhanced ALD using different precursors and oxidizing agents on n-type Si substrates to vary both defect concentration and crystallinity of the films. In addition, the defect concentration, which is typically dominated by oxygen vacancies, is manipulated by post-annealing treatments in oxidizing atmosphere. The successful removal of defects is confirmed by analysis of sub-bandgap absorption using photothermal deflection spectroscopy. Grazing incidence X-ray diffractometry and Raman spectroscopy further prove changes in the film structure from amorphous to anatase phase upon annealing. Supplementing the optical and structural characteristics, the role of film structure and defect concentration on charge injection across the interface into the electrolyte during water oxidation is investigated using photoelectrochemical methods.