Ultrathin Lutetium Oxide Film as an Epitaxial Hole‐Blocking Layer for Crystalline Bismuth Vanadate Water Splitting Photoanodes

Abstract

Here a novel ultrathin lutetium oxide (Lu 2 O 3 ) interlayer is integrated with crystalline bismuth vanadate (BiVO 4 ) thin film photoanodes to facilitate carrier transport through atomic-scale interface control. The epitaxial Lu 2 O 3 interlayer fabricated by pulsed laser deposition features very few structural defects at the back contact of the heterojunction, and forms a unique band alignment that favors photohole blocking. An optimized interlayer thickness of 1.4 nm significantly enhances charge separation efficiency and photocurrent. Combined with photoelectrochemical characterization, solid-state electronic, and localized conductive atomic force microscopy measurements, it is revealed that the Lu 2 O 3 interlayer modulates the electronic conduction pathways along structural grain boundaries and determines the overall device performance. This study sheds light on the nature of interface-engineered carrier transport for efficient photoelectrode heterostructure design.

Photoelectrochemical Device Designs toward Practical Solar Water Splitting: A Review on the Recent Progress of BiVO4 and BiFeO3 Photoanodes

“…In general, the establishment of epitaxial thin film photoelectrode has been widely recognized to maximize the potential of photoelectrode materials in pursuit of a further breakthrough by exploring its fundamental properties. For that reason, recently, various research on the growth of the epitaxial BiVO 4 have been reported, to explore its fundamental properties for PEC water splitting [13,19,[56][57][58][59][60][61][62][63]. Based on many theoretical predictions, the research related to the growth of the epitaxial monoclinic BiVO 4 (a = 5.1956 Å, b = 5.0935 Å, c = 11.6972 Å, β = 90.387 • ) films have been focused on growth along the c-axis.…”

“…The growth of epitaxial BiVO 4 (001) thin films also could be achieved on the SrTiO 3 (001) (STO, a = 3.905 Å) substrate by the insertion of the WO 3 as template layer, which could reduce the lattice mismatch between the BiVO 4 and the STO [13]. In addition, Zhang et al reported on the improved PEC performance of the epitaxial BiVO 4 (001) thin film by inserting lutetium oxide (Lu 2 O 3 ) as a hole blocking layer [60].…”

Boosting the Performance of BiVO4 Prepared through Alkaline Electrodeposition with an Amorphous Fe Co‐Catalyst

“…Among these methods, BiVO 4 doping, photocharging, cathodic polarization, nanostructuring,, as well as its interfacing with: highly active OER co‐catalysts ( cocats ) another SC and plasmonic materials, have shown great promise. The synthesis of photoelectrochemically active BiVO 4 on a conductive substrate is thus of great importance and can be performed by: i ) spray‐based,,, or ii ) hydrothermal, methods, iii ) metal‐organic decomposition,,, iv ) physical vapor deposition, and v ) electrodeposition ,. The latter approach is very attractive due to its simplicity and its low cost, and electrodeposited BiVO 4 has already led to very important breakthroughs ,.…”

Atomic Layer Deposition of Space‐Efficient SnO2 Underlayers for BiVO4 Host–Guest Architectures for Photoassisted Water Splitting

“…For n‐type materials like BiVO 4 , the underlayer is sometimes called a hole blocking layer or a “hole mirror.” Previous works have commonly utilized tin oxide (SnO 2 ) and tungsten oxide (WO 3 ), where SnO 2 is perhaps the most studied underlayer material for BiVO 4 . Other materials that have been used as interfacial layers in BiVO 4 photoanodes include TiO 2 , Lu 2 O 3 , and GaO x N 1‐ x ; SnO 2 was selected for this study based on its suitable band alignment relative to BiVO 4 , stability, low cost, and as‐yet unexplored investigation as a BiVO 4 underlayer using atomic layer deposition (ALD). Popular synthetic methods for SnO 2 , such as spray pyrolysis, yield optimal PEC performance with 65–80 nm of underlayer thickness .…”