Angstrom Thick ZnO Passivation Layer to Improve the Photoelectrochemical Water Splitting Performance of a TiO2 Nanowire Photoanode: The Role of Deposition Temperature

Karadaş

et al. 2019

Plasmonics

Self Cite

In this paper, we demonstrate a highly efficient light trapping design that is made of a metal-oxide-semiconductor-semiconductor (nanograting/nanopatch) (MOSS g/p) four-layer design to absorb light in a broad wavelength regime in dimensions smaller than the hole diffusion length of the active layer. For this aim, we first adopt a modeling approach based on the transfer matrix method (TMM) to find out the absorption bandwidth (BW) limits of a simple hematite (α-Fe 2 O 3)-based metal-oxide-semiconductor (MOS) cavity design. Our modeling findings show that this design architecture can provide near-perfect absorption in shorter wavelengths. To extend the absorption toward longer wavelengths, a nanostructured semiconductor is placed on top of this MOS design. This nanostructure supports the Mie resonance and adds a new resonance in longer wavelengths without disrupting the lower wavelength absorption capability of MOS cavity. By this way, a polarization-insensitive absorption above 0.8 can be acquired up to λ=565 nm. Moreover, to have a better qualitative comparison, the water-splitting photocurrent of this design has been estimated. Our calculations show that a photocurrent as high as 10.6 mA cm −2 can be achieved with this design that is quite close to the theoretical limit of 12.5 mA cm −2 for hematite-based water-splitting photoanode. This paper proposes a design approach in which the superposition of cavity modes and Mie resonances can lead to a broadband, polarization-insensitive, and omnidirectional near-perfect light absorption in dimensions smaller than the carrier's diffusion length. This can be considered as a winning strategy to design highly efficient and ultrathin optoelectronic designs in a variety of applications including photoelectrochemical water splitting and photovoltaics.

Section: Introductionmentioning

confidence: 99%

Highly Efficient Semiconductor-Based Metasurface for Photoelectrochemical Water Splitting: Broadband Light Perfect Absorption with Dimensions Smaller than the Diffusion Length

Karadaş

et al. 2019

Plasmonics

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“…For the investigation of the existence of surface defects, the O 1s spectra of the samples were analyzed. The core‐level O 1s spectrum of as‐prepared BiVO 4 is deconvoluted into three Gaussian peaks, as explained in our previous study . The major O 1s peak at around 529.30 eV is attributed to the lattice oxygen atoms (O L ) in the metal oxide.…”

Section: Resultsmentioning

confidence: 96%

Strong Light–Matter Interactions in Au Plasmonic Nanoantennas Coupled with Prussian Blue Catalyst on BiVO₄ for Photoelectrochemical Water Splitting

Soydan

et al. 2020

ChemSusChem

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A facial and large‐scale compatible fabrication route is established, affording a high‐performance heterogeneous plasmonic‐based photoelectrode for water oxidation that incorporates a CoFe–Prussian blue analog (PBA) structure as the water oxidation catalytic center. For this purpose, an angled deposition of gold (Au) was used to selectively coat the tips of the bismuth vanadate (BiVO4) nanostructures, yielding Au‐capped BiVO4 (Au‐BiVO4). The formation of multiple size/dimension Au capping islands provides strong light–matter interactions at nanoscale dimensions. These plasmonic particles not only enhance light absorption in the bulk BiVO4 (through the excitation of Fabry–Perot (FP) modes) but also contribute to photocurrent generation through the injection of sub‐band‐gap hot electrons. To substantiate the activity of the photoanodes, the interfacial electron dynamics are significantly improved by using a PBA water oxidation catalyst (WOC) resulting in an Au‐BiVO4/PBA assembly. At 1.23 V (vs. RHE), the photocurrent value for a bare BiVO4 photoanode was obtained as 190 μA cm−2, whereas it was boosted to 295 μA cm−2 and 1800 μA cm−2 for Au‐BiVO4 and Au‐BiVO4/PBA, respectively. Our results suggest that this simple and facial synthetic approach paves the way for plasmonic‐based solar water splitting, in which a variety of common metals and semiconductors can be employed in conjunction with catalyst designs.

“…Chemical synthesis, chemical vapor deposition of 2D semiconductors (such as TMDs), and other innovative preparation and transfer routes can lead to substantial enhancement in the performance of these ultrathin optoelectronic designs. A further enhancement in the performance of these designs can be achieved by using ultrathin surface engineering where the electrical response is improved significantly while the optical response stays intact …”

Section: Light Trapping Schemesmentioning

confidence: 99%

Semiconductor Thin Film Based Metasurfaces and Metamaterials for Photovoltaic and Photoelectrochemical Water Splitting Applications

Advanced Optical Materials

Özbay

2019

Self Cite

throughput and large-scale compatibility. The photoactive material is generally composed of single or multiple semiconductor layers responsible for harvesting solar energy. This harvested solar irradiation can be used to generate electricity using photovoltaic (PV) devices, or it can be converted to chemical energy in the form of hydrogen which is the case for photoelectrochemical water splitting (PEC-WS). In both PV and PEC-WS applications, the ultimate goal is to establish an efficient photon capturing and electron collecting scheme to generate a huge number of photocarriers (including electron-hole pairs) with rational carrier dynamics (efficient charge generation, separation, and collection). This means that the device should be optically thick enough to generate high carrier's density and electrically thin enough to collect photogenerated carrier before they recombine. When light impinges a semiconductor surface, a part of the light is reflected back due to the mismatch between the air and the semiconductor layer refractive index. The rest will propagate within the bulk until it is fully absorbed by the semiconductor slab. The optical penetration depth (LPD) is defined as the depth at which the incident power falls to 1/e (≈37%) of its input value. This parameter differs from one semiconductor to another and it depends on the extinction coefficient (κ) of the In both photovoltaic (PV) and photoelectrochemical water splitting (PEC-WS) solar conversion devices, the ultimate aim is to design highly efficient, low cost, and large-scale compatible cells. To achieve this goal, the main step is the efficient coupling of light into active layer. This can be obtained in bulkysemiconductor-based designs where the active layer thickness is larger than light penetration depth. However, most low-bandgap semiconductors have a carrier diffusion length much smaller than the light penetration depth. Thus, photogenerated electron-hole pairs will recombine within the semiconductor bulk. Therefore, an efficient design should fully harvest light in dimensions in the order of the carriers' diffusion length to maximize their collection probability. For this aim, in recent years, many studies based on metasurfaces and metamaterials were conducted to obtain broadband and near-unity light absorption in subwavelength ultrathin semiconductor thicknesses. This review summarizes these strategies in five main categories: light trapping based on i) strong interference in planar multilayer cavities, ii) metal nanounits, iii) dielectric units, iv) designed semiconductor units, and v) trapping scaffolds. The review highlights recent studies in which an ultrathin active layer has been coupled to the above-mentioned trapping schemes to maximize the cell optical performance.