Photoelectrochemical properties of single-grain hematite films grown by electric-field-assisted liquid phase deposition

This article reports a modification of the conventional liquid phase deposition (C-LPD) method for the single-grain deposition of α-Fe2O3 (hematite) films into an electric-field-assisted liquid phase deposition (EA-LPD). The latter is similar to C-LPD except that a conductive substrate, such as fluorine-doped tin oxide (FTO)-coated glass, is connected to the negative side of a direct current power supply, and a neutral electrode, such as a graphite rod, is connected to the positive side of the power supply. Microstructure studies suggest that the films deposited by EA-LPD have single grains along their thickness, with fewer grain boundaries than their multigrain counterpart films. The single-grain films exhibited a photocurrent density of 0.50 mA cm-2 at 1.23 vs. reversible hydrogen electrode (RHE), threefold that of the films deposited using conventional liquid phase deposition (0.15 mA cm-2). Photoluminescence investigations confirmed the depression of the electron-hole recombination process for the single-grain films. This study shows that reducing the grain boundary is a highly efficient way to increase the photocurrent density for photoelectrochemical processes.