PhoMAS

This project aims to elucidate the electronic structure and the energetic band alignment at the heterointerfaces of photoelectrochemical multijunction devices. Understanding the band energy diagrams of photoelectrochemical devices in the vicinity of the electrolyte in relation to their relative energetic position and the formation of electronic surface states will help to understand the efficiency limiting factors of the whole device. The coupling of absorbers to chemical and electronic passivation layers as well as co-catalysts will be systematically investigated, mainly by electrochemical methods coupled in-vacuo to photoelectron spectroscopy. The density functional theory will allow a detailed interpretation of the experimental data and finally provide an atomistic view on the origin of the energetic orientations. Since the elementary processes of light absorption, charge separation and transfer, and multi-electron catalysis are closely related, we will focus on two established water-splitting multiple arrangements that have already shown high efficiencies but have not yet reached their physical limits: Silicon-based multiple arrays and III-V compound semiconductor-based tandem cells. The hereby identified ways to modify the electrical-electronic coupling of the heterointerfaces will also be investigated and evaluated under operating conditions in close collaboration with the other partners. For the long-term perspective of the research consortium, this project will provide generalized research approaches that can be transferred to other highly efficient multiple systems.