Combined Theoretical and Experimental Investigations of Atomic Doping To Enhance Photon Absorption and Carrier Transport of LaFeO3 Photocathodes

Perovskite-type lanthanum iron oxide, LaFeO3, is a p-type semiconductor that can achieve overall water splitting using visible light while maintaining photostability. These features make LaFeO3 a promising photocathode candidate for various photoelectrochemical cells. Currently, the photoelectrochemical performance of a LaFeO3 photocathode is mainly limited by considerable bulk electron-hole recombination. This study reports a combined theoretical and experimental investigation on the atomic doping of LaFeO3, in particular, substitutional doping of La3+ with K+, to increase its charge-transport properties and decrease electron-hole recombination. The computational results show that K-doping enhances not only the charge-transport properties but also photon absorption below the bandgap energy of the pristine LaFeO3. The effect of K-doping was systematically investigated by comparing the electronic and atomic structures, majority carrier density, hole-polaron formation, and optical properties of pristine and K-doped LaFeO3. The computational results were then verified by experimentally characterizing the crystal structures, compositions, optical properties, and photoelectrochemical properties of LaFeO3 and K-doped LaFeO3 electrodes. For this purpose, pristine LaFeO3 and K-doped LaFeO3 were prepared as high- surface-area, high-purity photoelectrodes having the same morphology to accurately and unambiguously evaluate the effect of K-doping. The combined computational and experimental investigations presented in this study provide useful insights into the effect of composition tuning of LaFeO3 and other p-type oxides with a perovskite structure.