Improved photoelectrode performance of chemical solution-derived Bi2O3 crystals via manipulation of crystal characterization

Abstract

Three-dimensional Bi2O3 crystals with various morphologies were successfully synthesized on F-doped tin oxide substrates with and without homoseed layers via chemical bath deposition (CBD) routes. The structural analysis reveals that control of the pH value of the reaction solution resulted in as-grown Bi2O3 crystals with nanosheet and plate morphologies. A lower pH value of the reaction solution engendered formation of a porous sheet-like morphology of Bi2O3; by contrast, a higher pH value of the reaction solution is favorable for formation of solid Bi2O3 plates on the substrates. Furthermore, a sputter coated Bi2O3 seed layer with dual alpha- and beta-Bi2O3 phases plays an important role in the CBD-derived Bi2O3 crystallographic structures. The Bi2O3 crystals formed via CBD processes without a sputter coated Bi2O3 homoseed layer demonstrated a high purity in beta-Bi2O3 phase; those grown with a homoseed layer exhibited a dual alpha/beta phase. The photoactive performance results show that construction of an alpha/beta-Bi2O3 homojunction in the CBD-derived Bi2O3 crystals substantially improved their photoactive performance. Comparatively, the porous Bi2O3 nanosheets with a dual alpha/beta-Bi2O3 phase demonstrated the highest photoactive performance among various Bi2O3 crystals in this study. The superior photoactivity of the porous alpha/beta-Bi2O3 nanosheets herein is attributed to their high light absorption capacity and photoinduced charge separation efficiency. The experimental results in this study provide a promising approach to design CBD-derived Bi2O3 crystals with desirable photoelectric conversion functions via facile morphology control and seed layer crystal engineering.