Johanna Eichhorn

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Transition metal oxide and nitride semiconductors show promise for application in solar energy conversion. However, their efficiencies and stabilities are often controlled by the presence of defects as well as nanoscale chemical and physical heterogeneities. These material properties must be understood and controlled to enable their implementation in functional systems. Here, recent experimental advances in understanding nanoscale defect and interface properties will be presented, which are key to optimizing material properties, corrosion protection, and catalyst layers for solar energy conversion.

Economically viable and scalable photosystems often use polycrystalline thin films with complex structures, where grain boundaries, facet orientations, and composition variations affect their photoelectrochemical properties. For copper vanadate thin films, we correlated local structural, chemical, and optoelectronic properties with their photoelectrochemical performance to link nanoscale and macroscale characteristics for designing durable and efficient photosystems. [1]

Furthermore, we synthesized Ta3N5 thin film photoelectrodes with differing degrees of structural disorder and defect concentrations to reveal the relationship between atomic-scale point defects and macroscale photoelectrochemical stability. Specifically, we showed that shallow oxygen donors can kinetically stabilize the interface, whereas deep-level defects facilitate rapid photocarrier trapping and surface oxidation. [2]

To stabilize and activate their surface, we interfaced photoelectrodes with conformal and nanoscale layers that maintain chemical stability, enable efficient interfacial charge transport, and minimize parasitic light absorption. In particular, we leveraged unsaturated oxidation conditions in plasma-enhanced atomic layer deposition to synthesize cobalt oxide layers with tailored catalytic activities and chemical stabilities. [3]

References
[1] J. Eichhorn et al., ACS Appl. Mater. Interfaces 13, 23575 (2021).
[2] L. M. Wolz et al., Adv. Funct. Mater. 34, 2405532 (2024).
[3] M. Kuhl et al., Adv. Mater. Inter. 9, 2200582 (2022).

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TUM
Seminarraum PH1
Contact: Erwann Bocquillon / Matteo Cacco