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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.