Alternative Photoanode Research Articles

Enhancing Low–Bias performance of n–type Cu2O photoanode for solar water splitting via simultaneously accelerated charge transfer kinetics at back contact and liquid junction

Poor low–bias PEC performance of state–of–the–art BiVO4, α–Fe2O3 and WO3 photoelectrodes widely used in tandem and/or parallel PEC/PV and/or PEC/PEC devices has been reported to largely limit the cell efficiency for self–biased solar water splitting. A breakthrough of such bottleneck is put forward in this contribution by employing n–Cu2O with advantageous band edge positions straddling the HER and OER redox potentials as an alternative photoanode. The ohmic Cu/n–Cu2O back contact facilitates the interfacial photoelectron transfer while the gradient distribution of the oxygen vacancies (Vo) close to the n–Cu2O/electrolyte junction promotes the photoholes injected into water, synergistically leading to an outstanding photocurrent density of 3.5 mA cm−2, an unprecedented photocurrent–to–O2 conversion efficiency exceeding 70%, and a record ABPE of 2% at an ultralow applied potential of ∼0.6 VRHE, among the highest performance and the lowest external bias of state–of–the–art metal–oxide–based photoanodes reported to date.

Key modification strategies for the rational design of hematite to promote photoelectrochemical water oxidation: a review of recent advances

In this review article, multiple modification strategies for hematite, including controlling the morphology, heterojunction engineering, doping engineering, modification of co-catalyst and other modifications are proposed.

A comparison of investigations into the photovoltaic and electronic properties of the zinc-containing photoanodes for DSC applications

The study aimed to explore the possibility of using zinc oxide (ZO), zinc titanate (ZT), and zinc stannate (ZS) as alternative photoanode materials for DSC. The sol-gel process was used to synthesize the three materials. The prepared materials were characterized structurally by PXRD. UV-Visible spectroscopy was used to evaluate the absorption properties, dye loading, and aggregation behaviour of bare dye and dye-adsorbed photoanodes. As a result, ZS-based photoanodes have a high adsorption capacity (44 nmol/mg) and are less prone to aggregation. The photoelectric conversion behaviour of the materials was explored under one sunlight condition. It shows that ZS-based photoanodes have a higher photocurrent of 4.21 mA/cm 2 , a photovoltage of 0.613 V, and a better PCE of 1.66%, which can be attributed to the strong dye adsorption capacity of ZS. Similarly, photochemical data show a low R ct resistance and a high chemical capacitance for ZS. Zinc orientated with tin is viewed as a future DSC material that is less aggregative, low-cost, and high-performance than other derivatives. The details are presented herein. • An efficient comparison in PCE was conducted between several zinc-incorporated photoanodes (ZnO, ZnTiO 3 and ZnSnO 3 ). • The various photoanodes with zinc insertion were thoroughly examined regarding their electrochemistry and optical characteristics. • Zinc stannate (ZS) based photoanode exhibits higher device performance and is noted as a prospective candidate for DSC's future.

Effect of Varying AgNO3 and CS(NH2)2 Concentrations on Performance of Ag2S/ZnO NRs/ITO Photoanode

This research focuses on improving the photoelectrochemical performance of binary heterostructure Ag2S/ZnO NRs/ITO by manipulating synthesis conditions, particularly the concentrations of sliver nitrate AgNO3 and thiourea CS(NH2)2. The photoelectrochemical performance of Ag2S/ZnO nanorods on indium tin oxide (ITO) nanocomposite was compared to pristine ZnO NRs/ITO photoanode. The hydrothermal technique, an eco-friendly, low-cost method, was used to successfully produce Ag2S/ZnO NRs at different concentrations of AgNO3 and CS(NH2)2. The obtained thin films were characterized using field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), ultraviolet-visible spectroscopy (UV-vis), and photoelectrochemical studies (PECs). We observed that there was an enhancement in absorbance in the visible region and effective photoelectron transfer between the Ag2S/ZnO NRs/ITO photoelectrode and the electrolyte Red-Ox when illuminated with 100 mW cm−2. Increasing the concentration of AgNO3 caused a remarkable decrease in the optical bandgap energy (Eg) values. However, we noticed that there was an unstable trend in Eg when the concentration of CS(NH2)2 was adjusted. The photoelectrochemical studies revealed that at a bias of 1.0 V, and 0.005 M of AgNO3 and 0.03 M of CS(NH2)2, the maximum photocurrent of the Ag2S/ZnO NRs/ITO photoanode was 3.97 mA/cm2, which is almost 11 times that of plain ZnO nanorods. Based on the outcomes of this investigating, the Ag2S/ZnO NRs/ITO photoanode is proposed as a viable alternative photoanode in photoelectrochemical applications.

Synthesis and characterisation of heteroatom-doped reduced graphene oxide/bismuth oxide nanocomposites and their application as photoanodes in DSSCs.

Semiconductor materials have been recently employed in photovoltaic devices, particularly dye-sensitized solar cells (DSSCs), to solve numerous global issues, especially the current energy crisis emanating from the depletion and hazardous nature of conventional energy sources, such as fossil fuels and nuclear energy. However, progress for the past years has been mainly limited by poor electron injection and charge carrier recombination experienced by DSSCs at the photoanode. Thus, novel semiconductor materials such as bismuth oxide (Bi2O3) have been investigated as an alternative photoanode material. In this study, Bi2O3 was integrated with nitrogen- or boron-doped reduced graphene oxide (N-rGO or B-rGO, respectively) via a hydrothermal approach at a temperature of 200 °C. Various instrumental techniques were used to investigate the morphology, phase structure, thermal stability, and surface area of the resulting nanocomposites. The incorporation of N-rGO or B-rGO into Bi2O3 influenced the morphology and structure of the nanocomposite, thereby affecting the conductivity and electrochemical properties of the nanocomposite. B-rGO/Bi2O3 exhibited a relatively large surface area (65.5 m2 g−1), lower charge transfer resistance (108.4 Ω), higher charge carrier mobility (0.368 cm2 V−1 s−1), and higher electrical conductivity (6.31 S cm−1) than N-rGO/Bi2O3. This led to the fabrication of B-rGO/Bi2O3 photoanode-based DSSCs with superior photovoltaic performance, as revealed by their relatively high power conversion efficiency (PCE) of 2.97%, which outperformed the devices based on N-rGO/Bi2O3, rGO/Bi2O3, and Bi2O3 photoanodes. Therefore, these results demonstrate the promising potential of heteroatom-doped rGO/Bi2O3-based nanocomposites as photoanode materials of choice for future DSSCs.

Organic Semiconductors as Photoanodes for Solar-driven Photoelectrochemical Fuel Production.

The direct conversion of solar energy into chemical fuels, such as hydrogen, via photoelectrochemical (PEC) water splitting requires the efficient oxidation of water at a photoanode. While transition metal oxides have shown a significant success as photoanodes, their intrinsic limitations make them the bottleneck of PEC water splitting. Recently, initial research reports suggest that organic semiconductors (OSCs) could be possible alternative photoanode materials in both dye-sensitized and thin film photoelectrode configurations. Herein we review the progress to date, with a focus on the major issues faced by OSCs: stability and low photocurrent density in aqueous photoelectrochemical conditions. An outlook to the future of OSCs in photoelectrochemistry is also given.

Enhanced photovoltaic properties of dye-sensitized solar cells using three-component CNF/TiO2/Au heterostructure

To further increase the photoelectric efficiency of dye-sensitized solar cell (DSSC), enhancing the light adsorption of photoanode and suppressing the recombination of photo-generated charges are of great importance. Motivated by this, a novel and efficient three-component CNF/TiO2/Au heterostructure was successfully constructed and employed as an alternative photoanode material. The as-prepared CNF/TiO2/Au is characterized by conductive carbon nanofiber (CNF) core, uniform TiO2 outer shell assembled by upright nanorods, and surface modification with well-dispersed Au nanoparticles. To demonstrate the potential application of such material in DSSC, a comparison of photoelectric properties with commercial P25 and binary composite CNF/TiO2 was carried out. By contrast, the ternary composite CNF/TiO2/Au exhibited the highest short-circuit photocurrent density of 15.47 mA cm−2 and photoelectric conversion efficiency of 6.45%, which is about 31% higher than that of the commercial P25-based DSSCs. The great improvement of photoelectric properties for ternary composite CNF/TiO2/Au might be attributed to not only the conspicuous light adsorption ability derived from the sufficient dye loading of CNF/TiO2/Au and the surface plasmon resonance of Au nanoparticles, but also the reduced recombination endowed by the conductive CNF core and the heterojunctions at the interface.

Polyaniline-Layered Rutile TiO2 Nanorods as Alternative Photoanode in Dye-Sensitized Solar Cells.

In this paper, dye-sensitized solar cell (DSSC) performance of the less explored polymorph of TiO2, rutile, has been explored, and its performance has been modified with polyaniline (PANI) wrapping on the surface. For this purpose, highly crystalline rutile nanorods have been synthesized without any growth-directing substrates, employing a hydrothermal treatment. Further, to understand the phase composition and morphology, the synthesized nanorods and PANI-layered nanorods have been characterized through various physicochemical methods. The synthesized rods were implemented as photoanode material for DSSCs which exhibited a photoelectric conversion efficiency (PCE) of 4.28% with a high open-circuit voltage (VOC) of 0.84 V which is highly superior to DSSC with Degussa P25 (PCE = 3.95%) TiO2 nanoparticles. The resultant PCE of the nanorods was further enhanced to 6.23% on in situ deposition of PANI which acts as an electron-transporting layer. Introduction of conducting PANI over the rutile rod was explored as a new concept to improve the performance of photoanode material besides conventional TiCl4 treatment or scattering layer deposition.

Perforated BaSnO3 Nanorods Exhibiting Enhanced Efficiency in Dye Sensitized Solar Cells

Here, we report the synthesis of phase pure perforated porous BaSnO3 (BSO) nanorods and their application as an alternative photoanode in dye sensitized solar cells (DSSCs). BaSnO3, synthesized using different amounts of dextran, has been characterized through various physicochemical techniques to understand the effect of dextran in controlling its morphology. The porous morphology of the rod facilitated enhanced N719 dye loading capability within a very short duration of 20 min. The dye adsorption behavior of the nanorod has been monitored through UV–vis absorption spectroscopy and contact angle measurements. Further, as an alternative photoanode, a DSSC of active area 0.2826 cm2 fabricated with the porous BaSnO3 exhibited a maximum efficiency of 4.31% with a significantly high VOC of 0.82 V whereas, after TiCl4 treatment, the same cell exhibited an enhanced efficiency of 6.86% under 1 sun AM 1.5. On the basis of our results, we are able to establish porosity as an important factor in reducing the time r...

Self-Assembly of ZnO-Nanorods and Its Performance in Quasi Solid Dye Sensitized Solar Cells

Zinc oxide (ZnO) nanorods (NRs) were successfully prepared by self-assembly methods using zinc nitrate hexahydrate and hexamethylenetetramine as raw materials. ZnO-NRs were grown on FTO/ZnO seed layer and to enhance dye adsorption it was continued by deposition of titania (TiO2) paste by screen printing method. Deposition time of ZnO-NRs were varied, for 120, 150 and 180 minutes and subsequently stacked with one layer of TiO2 mesoporous. The resulting heterojunction layers of FTO/ZnO-Nrs/TiO2 was then applied as a photoanode in quasi-solid dye sensitized solar cell (QS- DSSC) with polymer gel electrolyte (PGE) as a hole conductor. UV-Vis spectrometer was used to investigate the changes of dye adsorption in photoanode with/without inserting titania mesoporous. Characterizations of scanning electron microscopy (SEM) and X-ray diffraction was carried out and the results shows that increasing the deposition time produces a smaller average grain size, diameter and denser layer of ZnO-nanorods. From current-voltage measurement, higher efficiency (η = 2.53%) was obtained for 120 min ZnO nanorods with short circuit current density (Jsc ) of 2.84 mA/cm2 and open circuit voltage (Voc) of 0.7 V. The combination of TiO2 and ZnO-NRs shows a better performance in solar cells characteristics due to increases of dye adsorption on photoanode and high photogenerated electron transport rate. This work emphasizes an optimum condition of ZnO-NRs in combination with TiO2 mesoporous as an alternative photoanode in QS-DSSC.

Preparation of Carbon Nanotube/TiO2 Mesoporous Hybrid Photoanode with Iron Pyrite (FeS2) Thin Films Counter Electrodes for Dye-Sensitized Solar Cell.

Multi-walled carbon nanotube (MWCNT)/TiO2 mesoporous networks can be employed as a new alternative photoanode in dye-sensitized solar cells (DSSCs). By using the MWCNT/TiO2 mesoporous as photoanodes in DSSC, we demonstrate that the MWCNT/TiO2 mesoporous photoanode is promising alternative to standard FTO/TiO2 mesoporous based DSSC due to larger specific surface area and high electrochemical activity. We also show that iron pyrite (FeS2) thin films can be used as an efficient counter electrode (CE), an alternative to the conventional high cost Pt based CE. We are able to synthesis FeS2 nanostructures utilizing a very cheap and easy hydrothermal growth route. MWCNT/TiO2 mesoporous based DSSCs with FeS2 CE achieved a high solar conversion efficiency of 7.27% under 100 mW cm−2 (AM 1.5G 1-Sun) simulated solar irradiance which is considerably (slightly) higher than that of A-CNT/TiO2 mesoporous based DSSCs with Pt CE. Outstanding performance of the FeS2 CE makes it a very promising choice among the various CE materials used in the conventional DSSC and it is expected to be used more often to achieve higher photon-to-electron conversion efficiencies.

Enhanced stability of Zn2SnO4 with N719, N3 and eosin Y dye molecules for DSSC application.

In view of the increased prospects of Zn2SnO4 as an alternative photoanode for dye sensitized solar cells (DSSCs), we synthesized phase pure Zn2SnO4 nanostructures by a cost effective sonochemical technique. In order to establish the stability of this alternative photoanode in DSSCs, we further explored the interaction of the synthesized Zn2SnO4 with commonly used photosensitizers in DSSCs, such as N3, N719 and eosin Y. Based on the time dependent optical studies we could establish the prominence of anchoring groups in controlling the dye loading. Optical studies confirmed an enhanced stable interaction of Zn2SnO4 with all the studied sensitizers which could be beneficial in designing DSSC devices in future. In addition, we also established contact angle measurement as an indirect tool to understand the surface characteristics and thereby optimize the dye loading and stability of the photoanode surface. With the help of contact angle data, we could unequivocally establish the stability of the Zn2SnO4 photoanode surface modified with N3 and N719 dye molecules. Our studies further suggest the enhanced and superior stability of the prepared Zn2SnO4 compared to ZnO in different chemical environments. The quenching of the fluorescence and the abrupt decrease in the contact angle owing to an increase in the surface roughness further strengthen the above conclusion. To our best knowledge, this probably is the first report on the synthesis of Zn2SnO4 by a sonochemical process and its interaction with various photosensitizers. An exceptionally high open circuit voltage of >0.8 V was observed for all the devices fabricated with the synthesized ZTO as a photoanode. Our studies could pave way to future developments in the area of DSSCs using Zn2SnO4 as a photoanode.

Nanostructured Carbon-TiO<SUB>2</SUB> Shells Onto Silica Beads as a Promising Candidate for the Alternative Photoanode in Dye-Sensitized Solar Cells

Nanostructured Carbon-TiO<SUB>2</SUB> Shells Onto Silica Beads as a Promising Candidate for the Alternative Photoanode in Dye-Sensitized Solar Cells

Dye-sensitized solar cells using double-oxide electrodes: a brief review

Dye-sensitized solar cells (DSC or DSSC) have been widely investigated because of their potentially high cost performance compared with Si-based solar cells and of their fascinating appearance. DSC with photoelectric conversion efficiency of >10 % (or even 12 %) have been reported, where porous TiO2 films are generally used as semi-conductor electrodes. Such porous TiO2 films usually have high specific surface area, and thus, they adsorb plenty of dye molecules, resulting in high photocurrent density. Recently, some double oxides have been examined as alternative photoanode materials, mainly in order to improve photovoltage. Here, studies on DSC using double-oxide electrodes, i.e., perovskite, spinel, ilmenite, wolframite, scheelite and pseudobrookite-types, are briefly reviewed.

Development in Photoanode Materıals for Highly Efficient Dye Sensitized Solar Cells

Dye-sensitized solar cells (DSSC) have been extensively studied due to their promising potential for high efficiency, low production cost and eco-friendly production. The photoanode is one of the main components in DSSCs which determines its performance. The main issues facing in DSSCs are the charge recombinations and low light harvesting capacity. Conventional TiO 2 nanoparticles with large surface area has low light scattering ability and low electron transport rate while one dimensional nanostructures have high electron transport rate and good light scattering ability but has a low surface area. Different approaches such as nanocomposite, light scattering layer and hierarchical structures to improve performance of 1D DSSCs are discussed. Besides that, works done on the optimization of TiO 2 photoanode in cobalt based DSSC is also discussed. Additionally, doping of TiO 2 to improve the properties of TiO 2 and studies on alternative photoanode materials which involved the application of band gap engineering are discussed to further improve the performance of DSSCs.

RETRACTED: Photocurrent enhancement by Ni2+ and Zn2+ ion doped in SnO2 nanoparticles in highly porous dye-sensitized solar cells

Searching on alternative photoanode materials for dye-sensitized solar cells (DSSCs) evidenced that rare works have been reported on studying Ni2+ and Zn2+ doped SnO2 nanoparticles. Mostly efficient DSSCs with perfect long-term stability were fabricated based on tin (IV) oxide (SnO2) nanocrystals doped with different metals ions. The co-precipitation technique was applied to prepare M-doped SnO2 nanoparticles. Moreover, the obtained powders were investigated using XRD, HRTEM, BET specific surface area (SBET) and UV–vis spectroscopy. In addition, an economic way to prepare semiconducting pastes for photoanodes was devised. The photovoltaic performance of dye-sensitized solar cells based on undoped and Ni2+ and Zn2+ doped SnO2 photoanodes was investigated. Zn and Ni doped SnO2, respectively, have a high power conversion efficiency of up to 4.2% and 3.6%, higher than that of undoped SnO2 which is 3.2% and the reason for this difference is that the Zn and Ni-doped films exhibit an elevated electron Fermi level, which may enhance band bending to lower the density of empty trap states. On account of these doping metals, the consequent DSSCs can alleviate the decay of light to electric energy conversion efficiency due to light intensity reduction. The enhanced transport of photogenerated electrons as a result of the trap density minimization is responsible for the high photovoltaic performance.

PbS/CdS-sensitized mesoscopic SnO2 solar cells for enhanced infrared light harnessing

Metal oxide semiconductors with lower lying conduction band minimum and superior electron mobility are essential for efficient charge separation and collection in PbS-sensitized solar cells. In the present study, mesoscopic SnO(2) was investigated as an alternative photoanode to the commonly used TiO(2) and examined comprehensively in PbS-sensitized liquid junction solar cells. To exploit the capability of PbS in an optimized structure, cascaded nPbS/nCdS and alternate n(PbS/CdS) layers deposited by a successive ionic layer adsorption and reaction method were systematically scrutinized. It was observed that the surface of SnO(2) has greater affinity to the growth of PbS compared with TiO(2), giving rise to much enhanced light absorption. In addition, the deposition of a CdS buffer layer and a ZnS passivation layer before and after a PbS layer was found to be beneficial for efficient charge separation. Under optimized conditions, cascaded PbS/CdS-sensitized SnO(2) exhibited an unprecedented photocurrent density of 17.38 mA cm(-2) with pronounced infrared light harvesting extending beyond 1100 nm, and a power conversion efficiency of 2.23% under AM 1.5, 1 sun illumination. In comparison, TiO(2) cells fabricated under similar conditions showed much inferior performance owing to the less efficient light harnessing of long wavelength photons. We anticipate that the systematic study of PbS-sensitized solar cells utilizing different metal oxide semiconductors as electron transporters would provide useful insights and promote the development of semiconductor-sensitized mesoscopic solar cells employing panchromatic sensitizers.

Dye-Sensitized Solar Cells Based on WO3

In research on alternative photoanode materials for dye-sensitized solar cells (DSCs), there is rarely any report on WO(3), probably due to its acidic surface and more positive (vs NHE) conduction band edge position compared to TiO(2) and ZnO. For the first time, dye-sensitized solar cells based on porous WO(3) nanoparticle films were successfully fabricated with efficiency of up to 0.75%. The multicrystalline structure of WO(3) was examined by Raman spectroscopy and X-ray diffraction analysis. It was found that significant performance enhancement can be obtained from treating the WO(3) nanoparticle film with TiCl(4); the TiCl(4)-treated WO(3) DSCs were recorded with efficiency reaching 1.46%.

PREPARATION OF MESOPOROUS ZnO MICROSPHERES AND THEIR APPLICATION IN DYESENSITIZED SOLAR CELLS

A novel ZnO photoanode with high specific surface area and good light scattering ability was fabricated for dye-sensitized solar cells(DSSCs).The photoanode comprised of mesoporous ZnO microspheres which were prepared by a solvothermal process.The structures and morphologies of ZnO microspheres were measured and confirmed by means of x-ray diffraction(XRD),scanning electron microscopy(SEM),energy dispersive spectrum(EDS),and multi-point Brunauer-Emmett-Teller(BET) analysis.ZnO microspheres are in sub-micrometer scale and have BET specific surface area of ~50m2·g-1.Furthermore,a~3μm thick photoanode made from ZnO microspheres resultes in a preliminary short-circuit current density(Jsc) of ~4.5mA·cm-2 with an open-circuit voltage(Voc) of ~602mV and a conversion efficiency of 1.28% in DSSCs.All these suggest that mesoporous ZnO microspheres can be an alternative and feasible photoanode material for DSSCs.

New Architectures for Dye‐Sensitized Solar Cells

Modern dye-sensitized solar cell (DSSC) technology was built upon nanoparticle wide bandgap semiconductor photoanodes. While versatile and robust, the sintered nanoparticle architecture exhibits exceedingly slow electron transport that ultimately restricts the diversity of feasible redox mediators. The small collection of suitable mediators limits both our understanding of an intriguing heterogeneous system and the performance of these promising devices. Recently, a number of pseudo-1D photoanodes that exhibit accelerated charge transport and greater materials flexibility were fabricated. The potential of these alternative photoanode architectures for advancing, both directly and indirectly, the performance of DSSCs is explored.