ABSTRACT
Hematite photoanodes for photoelectrochemical (PEC) water splitting are often fabricated as extremely-thin films to minimize charge recombination because of the short diffusion lengths of photoexcited carriers. However, poor crystallinity caused by structural interaction with a substrate negates the potential of ultrathin hematite photoanodes. This study demonstrates that ultrathin Ga2O3 underlayers, which were deposited on conducting substrates prior to hematite layers by atomic layer deposition, served as an isomorphic (corundum-type) structural template for ultrathin hematite and improved the photocurrent onset of PEC water splitting by 0.2 V. The benefit from Ga2O3 underlayers was most pronounced when the thickness of the underlayer was approximately 2 nm. Thinner underlayers did not work effectively as a template presumably because of insufficient crystallinity of the underlayer, while thicker ones diminished the PEC performance of hematite because the underlayer prevented electron injection from hematite to a conductive substrate due to the large conduction band offset. The enhancement of PEC performance by a Ga2O3 underlayer was more significant for thinner hematite layers owing to greater margins for improving the crystallinity of ultrathin hematite. It was confirmed that a Ga2O3 underlayer was applicable to a rough conducting substrate loaded with Sb-doped SnO2 nanoparticles, improving the photocurrent by a factor of 1.4. Accordingly, a Ga2O3 underlayer could push forward the development of host-guest-type nanocomposites consisting of highly-rough substrates and extremely-thin hematite absorbers.
ABSTRACT
An overview of a collaborative experimental and theoretical effort toward efficient hydrogen production via photoelectrochemical splitting of water into di-hydrogen and di-oxygen is presented here. We present state-of-the-art experimental studies using hematite and TiO(2) functionalized with gold nanoparticles as photoanode materials, and theoretical studies on electro and photo-catalysis of water on a range of metal oxide semiconductor materials, including recently developed implementation of self-interaction corrected energy functionals.
ABSTRACT
Herein, we present a straightforward bottom-up synthesis of a high electron mobility and highly light scattering macroporous photoanode for dye-sensitized solar cells. The dense three-dimensional Al/ZnO, SnO(2), or TiO(2) host integrates a conformal passivation thin film to reduce recombination and a large surface-area mesoporous anatase guest for high dye loading. This novel photoanode is designed to improve the charge extraction resulting in higher fill factor and photovoltage for DSCs. An increase in photovoltage of up to 110 mV over state-of-the-art DSC is demonstrated.
Subject(s)
Coloring Agents/chemistry , Electric Power Supplies , Electrodes , Nanotechnology/instrumentation , Solar Energy , Coloring Agents/radiation effects , Equipment Design , Equipment Failure Analysis , LightABSTRACT
Herein, we present a novel morphology for solid-state dye-sensitized solar cells based on the simple and straightforward self-assembly of nanorods into a 3D fibrous network of fused single-crystalline anatase nanowires. This architecture offers a high roughness factor, significant light scattering, and up to several orders of magnitude faster electron transport to reach a near-record-breaking conversion efficiency of 4.9%.
ABSTRACT
We introduce a simple solution-based strategy to decouple morphological and functional effects of annealing nanostructured, porous electrodes by encapsulation with a SiO(2) confinement scaffold before high temperature treatment. We demonstrate the effectiveness of this approach using porous hematite (α-Fe(2)O(3)) photoanodes applied for the storage of solar energy via water splitting and show that the feature size and electrode functionality due to dopant activation can be independently controlled. This allows a significant increase in water oxidation photocurrent from 1.57 mA cm(-2) (in the control case) to 2.34 mA cm(-2) under standard illumination conditions in 1 M NaOH electrolyte-the highest reported for a solution-processed hematite photoanode. This increase is attributed to the improved quantum efficiency, especially with longer wavelength photons, due to a smaller particle size, which is afforded by our encapsulation strategy.
ABSTRACT
TiO(2) nanotube arrays prepared by electrochemical anodization of Ti foils show impressive light to electricity conversion efficiency in the dye-sensitized solar cells (DSCs). The length of the TiO(2) nanotube arrays (5-14 microm) was controlled by varying the anodization time from 2 to 20 h. The influence of nanotube lengths on the photovoltaic performance of DSCs was investigated by impedance. A flexible DSC using TiO(2) nanotube arrays on a Ti foil as a working electrode and polyethylene naphthalate (ITO/PEN) as counterelectrode in combination with solvent-free ionic liquid electrolyte achieved 3.6% photovoltaic conversion efficiency under simulated AM 1.5 sunlight.
