The research focuses on understanding the fundamental physicochemical properties of materials for energy conversion, with particular emphasis on three distinct categories: (i) ternary and quaternary metal oxides, (ii) high-entropy metal oxides, and (iii) oxynitride semiconductors. Ternary and quaternary metal oxides, composed of three or four different metal elements, offer diverse electronic, optical, and catalytic properties critical for applications in photovoltaics and photocatalysis. High-entropy metal oxides, characterized by five or more equimolar cations stabilized into a single-phase structure by configurational entropy, present a new frontier in material science. These materials exhibit unique structural stability and tunable properties, potentially surpassing conventional oxides in energy conversion efficiency. With their mixed anionic lattices, Oxynitride semiconductors offer an exciting avenue for solar energy conversion due to their tunable bandgaps and enhanced stability. The study delves into the synthesis-structure-property relationships in these materials, mainly their opto-electronic properties.

These material classes are challenging to synthesize in a pure phase (especially at sub-nanometers to nanometers regimes), which often may lead to non-optimized structures, enabling the study of their intrinsic properties in depth. Using our synthesis approaches (vide supra, novel synthesis methods section), we aim to comprehensively understand how the synthesis and structural characteristics affect the physicochemical properties of these materials. This research aims to unlock new pathways for developing highly efficient and stable materials for sustainable energy conversion.