Theoretical exploration of p-doped BiFeO3: models, screening, and applications

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The project has three intertwined research objectives, centered around the investigation of p-doped BiFeO3 (BFO) with the aim of finding suitable compositions for BFO p/n-junctions, in order to enable oxide electronics and photovoltaics. In the first research objective, it is planned to evaluate and refine effective theoretical models for production runs (such as hybrid-DFT and DFT+U) by adjusting their parameters in order to reproduce results obtained from highly accurate benchmark calculations (many body calculations including excitonic effects). Secondly, I want to screen suitable dopant cations for p-type doping in BFO with respect to their induced changes on the electronic structure and the polarization of BFO by standard DFT. The description of the most promising candidates will be refined with the refined methods obtained in the first part of the project. In addition, fabrication and experimental testing of the best dopant candidates is envisioned within an interdisciplinary study using already established collaborations at the host institute, which will enable the fabrication of BFO p/n-junctions in further steps. This part of the project will be carried out in a way that will allow to find trends with respect to the dopant ions, which in turn will allow the transfer of the obtained results to similar ferroelectric metal oxides. In the last research objective, the previously obtained results will be further processed by employing the expertise of the host group in the description of the bulk-photovoltaic effect (BPVE) to the studied systems and methods. This means, I want to investigate the effects that p-doping and the quality of the wave function have on the computed shift current, which was shown to be the dominant mechanism of the BPVE by Prof. Rappe and his group.In summary, the project covers the design and investigation of p-doped BFO from basis research and the development of a suitable, more accurate but feasible theoretical description, over intense but efficient screening in order to identify promising candidates, up to experimental synthesis of the developed materials and device fabrication. Thus, the project provides a systematic, intelligent material design of p-doped BFO and results that are transferable to similar host structures, contributing to the design and fabrication of metal oxide p/n-junctions and, thus, future oxide electronics and photovoltaics.