Hybrid Perovskite/Metal Oxide Heterojunctions as Bifunctional Electrodes in Photobatteries: Syntheses, Analyses and Structure-Property Relations (StoreLight)

• Applicant: Dr. Helen Grüninger
• Subject Area: Solid State and Surface Chemistry, Material Synthesis
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 565381591

Photobatteries, which convert and store solar energy by coupling a battery with a solar cell in a single system, represent a promising development for future energy supply. Photobatteries use bifunctional electrodes that can photogenerate charge carriers, chemically store ions and transport both. However, the field is still largely unexplored, and requires both the design of new materials or material composites as well as an in-depth understanding of interlocking photophysical and electrochemical processes. Therefore, the main objective of this project is the synthesis and characterization of bifunctional heterojunction electrodes based on hybrid perovskites as photoactive material in junction with metal oxides. The latter acts as electron or hole extraction material for the perovskite and as battery electrode storing reversibly Li+ or Na+ ions. We focus on TiO2 and V2O5 as model metal oxides to build the heterojunction with hybrid perovskites creating photoanodes and -cathodes. We will nanostructure the heterojunction interface to increase the efficiency for charge carrier generation and separation by both, an efficient illumination and maximized charge transfer at the junction interface. The nanostructure will further serve the battery function by maximizing metal oxide surfaces, reducing ion diffusion lengths and facilitating (dis)charging. A multitude of dynamic processes including electronic and ionic transport are crucial for the function of the bifunctional electrode. Thus, an emphasis lies in a comprehensive characterization of the individual heterojunction composites and photobattery devices (including in-situ/operando). First, we aim at understanding electronic processes of the nanostructured heterojunction composites during light harvesting, charge carrier transport and separation at the junction to the metal oxide. Secondly, we will evaluate ionic processes from (photo)electrochemical properties and structural analyses with a focus on reversible dynamic crystalline and/or amorphous phase transformations, and irreversible side reactions or degradation. Furthermore, we will focus on changes in band gap energies and band edge positions associated with (photo-)electrochemical phase transformations and their impact on band alignment and electronic transport. These electronic and ionic processes will be addressed by using optical spectroscopy, current-potential characteristics, (photo)electrochemical analyses, operando solid-state NMR spectroscopy and X-ray diffraction. The comprehensive characterization of physicochemical and structural properties will allow us to derive structure-function relations. Ideally, we will ultimately develop concepts for efficient and stable hybrid perovskite/metal oxide heterojunctions for photobatteries to serve both functionalities, i.e. energy harvest and storage, with high sustainability.

• DFG Programme: Emmy Noether Independent Junior Research Groups
• Major Instrumentation: LED 3.2mm MAS NMR Probe
• Instrumentation Group: 1741 Festkörper-NMR-Spektrometer