Dual Role of Sb-Incorporated Buffer Layers for High Efficiency Cuprous Oxide Photocathodic Performance: Remarkably Enhanced Crystallinity and Effective Hole Transport

Abstract

The high performance of electrodeposited cuprous oxide (Cu2O)-based photoelectrochemical (PEC) cells has been limited due to low electrical conductivity hindering effective carrier transport to electrodes and chemically unstable properties in aqueous environments, despite their several advantages such as suitable band gap, band position, and cost-effective and environmentally friend elements. To improve the fundamental photoelectrochemical properties of photocathode Cu2O layers, particularly their photocurrent and stability, we present a simple approach using a double-layer photocathode, where the double-layer structure consists of Sb-incorporated Cu2O (Cu2O:Sb) and undoped Cu2O. The Cu2O:Sb double layer enhanced the preferred crystal growth along the [111] direction, as well as the crystallinity of the Cu2O. This microstructural change resulted in high electrical conductivity owing to high hole mobility and the suppression of instability related to surface facets. Consequently, the introduction of Cu2O:Sb led to the simultaneous roles of seed crystal and effective hole transport, and our double-layer photoelectrodes have shown good photocurrent without any metal photocatalysts and relatively better photostability without the help of protection layers.

Cuprous/Cupric Heterojunction Photocathodes with Optimal Phase Transition Interface via Preferred Orientation and Precise Oxidation

“…As shown in Figure c, the absorbance of SL-5 is observably higher than that of DL-5 at the long wavelength of >500 nm. This is attributed to the strongly preferred orientation and vertically aligned grain boundaries in the double layer samples, as reported in our previous study . Even though general fact that high absorbance leads to the high photocurrent, but our experiment yielded opposite results.…”

“…In this study, we produced optimally aligned Cu 2 O/CuO heterostructure photocathodes by oxidizing the orientation-controlled Cu 2 O layers under reduced oxygen partial pressure. When the Cu 2 O films were preferentially oriented along the [111] direction by using the Cu 2 O:Sb buffer layer, the exposed facets mostly consisted of {200} crystal planes with three-faced pyramids . Subsequent thermal oxidation of the Cu 2 O:Sb/Cu 2 O double layer mitigated the defect formation at the Cu 2 O/CuO interface by minimizing lattice mismatch.…”

Optimal n-Type Al-Doped ZnO Overlayers for Charge Transport Enhancement in p-Type Cu2O Photocathodes

“…ALD is attracting increasing attention as an important deposition technology for the production of nanoscale transparent conductive oxide (TCO) films because it allows the deposition of thin films with excellent uniformity on various substrates. Although numerous ALD-based studies on Al-doped Zn-base oxides have been conducted [ 13 , 30 , 31 ], not many studies have focused on the effect of ZnO-based overlayers on the photoelectrochemical reaction.…”

Bundle-Type Columnar Cu2O Photoabsorbers with Vertical Grain Boundaries Fabricated Using Instant Strike-Processed Metallic Seeds and Their Enhanced Photoelectrochemical Efficiency

“…As photovoltaic technology improves, there are results of high-performance PEC water splitting using crystalline Si photoelectrodes. , However, single crystals of popular PEC absorber materials (BiVO 4 , Fe 2 O 3 , Cu 2 O, etc.) cannot readily be produced using inexpensive solution processes, such as sol–gel, hydrothermal, and electrodeposition. − In particular, the crystallinity of previously electrodeposited Cu 2 O photoabsorbers with stable p-type characteristics has been optimized by adjusting the typical electrochemical conditions, such as pH, applied potential, salt concentration, and temperature. , Nevertheless, conventional electrodeposition methods are not enough to control crystallinity. Hence, we propose the concept of a polycrystalline “bundle-type columnar structure” as a unique alternative structure, where individual crystal grains are well-aligned perpendicular to the substrate.…”