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HL: Fachverband Halbleiterphysik
HL 24: Functional semiconductors for renewable energy solutions I (joint session HL/CPP)
HL 24.5: Vortrag
Dienstag, 17. März 2020, 11:15–11:30, POT 151
Atomic-Layer-Deposited TiO2 protection layers for InP photocathodes — •Matthias Kuhl1, Oliver Bienek1, Alex Henning1, Agnieszka Paszuk2, Thomas Hannappel2 und Ian D. Sharp1 — 1Walter Schottky Institut, Technische Universität München — 2Institut für Physik, Technische Universität Ilmenau
InP has gained increased interest as a photocathode for solar fuels generation due to its suitable band gap of 1.34 eV, a conduction band edge slightly above the water reduction potential and a high incident photon to charge conversion efficiency (IPCE). While it has been found that a TiO2 passivation layer, grown by atomic layer deposition (ALD), improve the InP/TiO2 photocathode stability, the influence of the TiO2 optoelectronic properties on surface reactions and interfacial charge transfer is not yet understood.
Here we investigate the role of ultrathin TiO2 (<10nm), grown by plasma-enhanced ALD, its phase, as well as defect type and concentration for the photoelectrochemical (PEC) performance of InP/TiO2 photocathodes. Tetrakis(dimethylamino)titanium (TDMAT) and titanium isopropoxide (TTIP) as precursors as well as H2O and O2-Plasma as oxidants are used to grow ALD TiO2 films with different oxidation states and defect levels. X-Ray photoelectron spectroscopy of TiO2 grown by PE-ALD revealed only trace amounts of impurities and stoichiometric TiO2 consistent with a lower defect density measured by photothermal deflection spectroscopy. This work provides insights into how electronic properties of photocathode protection layers affect interfacial charge injection.