Conduction Band Tuning by Controlled Alloying of Fe into Cs2AgBiBr6 Double Perovskite Powders

• Published in: Advanced functional materials 2024-12, Vol.34 (50), p.n/a
• Main Authors: Jöbsis, Huygen J., Fykouras, Kostas, Reinders, Joost W.C., Katwijk, Jacco, Dorresteijn, Joren M., Arens, Tjom, Vollmer, Ina, Muscarella, Loreta A., Leppert, Linn, Hutter, Eline M.
• Format: Article
• Language: English
• Subjects: Absorption; Conduction bands; Density functional theory; DFT calculations; double perovskites; electronic structures; Energy gap; First principles; mechanochemical synthesis; Perovskites; photocatalysis; Photoredox catalysis; Photovoltaic cells; Semiconductors; Sunlight
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.202306106

Halide double perovskite semiconductors such as Cs2AgBiBr6 are widely investigated as a more stable, less toxic alternative to lead‐halide perovskites in light conversion applications including photovoltaics and photoredox catalysis. However, the relatively large and indirect bandgap of Cs2AgBiBr6 limits efficient sunlight absorption. Here, it is shown that controlled replacement of Bi3+ with Fe3+ via mechanochemical synthesis results in a remarkable tunable absorption onset between 2.1 and ≈1 eV. First‐principles density functional theory (DFT) calculations suggest that this bandgap reduction originates primarily from a lowering of the conduction band upon the introduction of Fe3+, and predict a direct bandgap when >50% of Bi3+ is replaced with Fe3+. The tunability of the conduction band energy is found and reflected in the photoredox activity of these semiconductors. These findings open new avenues for enhancing the sunlight absorption of double perovskite semiconductors and for harnessing their full potential in sustainable energy applications. Here, it is shown that controlled alloying of Cs2AgBiBr6 with Fe3+ via mechanochemical synthesis results in a tunable absorption onset between 2.1 and ≈1 eV. First‐principles density functional theory calculations suggest that this bandgap reduction originates from a lowering of the conduction band upon the introduction of Fe3+. These findings open new avenues for enhancing the sunlight absorption of double perovskite semiconductors.