Photoelectrochemical Solar Cells Research Articles

Si microwire array photoelectrochemical cells: Stabilized and improved performances with surface modification of Pt nanoparticles and TiO2 ultrathin film

Abstract To achieve the semiconductor photoelectrochemical (PEC) cells targeting the industry applications with commercial competitiveness, high efficiency and good stability are requisite properties. To improve the PEC response, the vertically-aligned silicon microwire arrays (SiMWAs) modified with isolated Pt nanoparticles (PtNPs) and conformal TiO 2 ultrathin film (TiO 2 /Pt@SiMWAs) are fabricated and examined in this study. The modified system shows the significantly enhanced responses and operation stability, that is, an enhancement of ∼30.0% in saturation photocurrent density ( J sat ), a cathodic shift of ∼0.85 V (relative to the bare SiMWAs) in applied potential for J sat , and an attenuation ratio of the photocurrent 2 ultrathin film protects the SiMWAs from photo-oxidation/corrosion as well as suppresses the surface recombination. Our results indicate a feasible route for the practical applications of oxidizable and corrodible semiconductor micro-/nanostructures in the fields of PEC solar cells, water splitting, photodegradation, and so on.

Fine Tuning of Colloidal CdSe Quantum Dot Photovoltaic Properties by Microfluidic Reactors

Colloidal quantum dots (QDs) are attractive materials for application in photovoltaic and photoelectrochemical devices, due to their unique properties including band energy tunability, high absorption coefficient and multiple exciton generation. Here, we construct continuous and automated microfluidic reactors for the synthesis of CdSe QDs, and apply the synthesized QDs to the QD-sensitized solar cells (QDSCs) as a photosensitizer. The spectral range, quantum yield (QY) and surface states of QDs are facilely and finely tuned by controlling the flow rates of precursor solutions and solvents in the microfluidic reactors. The photovoltaic and photoelectrochemical performances of QDSCs are strongly affected by both the spectral range and QY of CdSe QDs. In particular, the conversion efficiency is enhanced by about 19% with the increase in QY from 15.4% to 23.2%, at the same spectral range. Furthermore, the enhanced surface purity of QDs by modified synthetic condition leads to the reduced electron recombination in the QD-sensitized TiO2 electrodes, which is confirmed by electrochemical impedance analysis. This study demonstrates the great potential of microfluidic system for the synthesis QDs and their application in photoelectrochemical solar cells.

Nanostructure Zn–Cu co-doped CdS chalcogenide electrodes for opto-electric-power and H2 generation

An efficient photoanode of Zn–Cu: doped nanostructure CdS film has been fabricated by a very simple and commercially usable chemical bath deposition methodology. The electrodes of various sizes were deposited, those ranged from 10 × 10 mm to 100 × 100 mm. Physico-chemical property of the film is investigated in-depth for the photo-electrochemical (PEC) hydrogen production and electric-power generation application. Especially, we studied the effect of Zn and Cu co-doping in the hexagonal CdS-lattice w.r.t. the structural, optical and PEC properties of the nanostructure film. Zn-doping induces an increase in the absorption of visible light photons. The doping enhances the photocurrent by twice as to the undoped, and generates a net photocurrent of ∼817 μA/cm2, at a very low applied potential of 0.1 V/SCE, in contrast to 366 μA/cm2 of its undoped counterpart. Electrochemical impedance spectroscopy demonstrated that the reduced e–h recombination is responsible for the superior performance of the electrodes. PEC cell fabricated by these electrodes showed a maximum hydrogen generation rate of ∼6.74 μmol/h as compared to 0.58 μmol/h from undoped counterpart; Further a photo to electric-power conversion efficiency of ∼0.16% has been achieved even at low biasing potential of 0.1 V/SCE under AM 1.5 solar simulated illumination. Undoped, Zn doped and Cu co-doped films are highly useful for dual applications of “solar power-generation” and “solar hydrogen-generation”, revealing that the Zn doped PEC solar cell is most efficient system for the hydrogen generation even at a very low voltage bias of 0.1 V/SCE.

Optimization of Lead-free Organic–inorganic Tin(II) Halide Perovskite Semiconductors by Scanning Electrochemical Microscopy

Lead-free organic-inorganic tin halide perovskites were prepared and investigated by a rapid screening technique utilizing a modified scanning electrochemical microscope (SECM). We studied liquid junction photoelectrochemical (PEC) solar cells based on p-type methylammonium tin halide (MASnI3-xBrx) perovskites employing the benzoquinone (BQ) redox couple, BQ/BQ−, in dichloromethane (CH2Cl2). We found that the optimized Sn-based mixed halide perovskite, MASnI0.5Br2.5, exhibits enhanced performance and stability in liquid-junction PEC solar cells, with a power conversion efficiency of 1.51% (an increase of 20.8%) and a photovoltaic lifetime of 175min (an increase of 75.0%), in comparison to MASnI3 perovskites.

Integrated Photoelectrochemical Solar Energy Conversion and Organic Redox Flow Battery Devices

AbstractBuilding on regenerative photoelectrochemical solar cells and emerging electrochemical redox flow batteries (RFBs), more efficient, scalable, compact, and cost‐effective hybrid energy conversion and storage devices could be realized. An integrated photoelectrochemical solar energy conversion and electrochemical storage device is developed by integrating regenerative silicon solar cells and 9,10‐anthraquinone‐2,7‐disulfonic acid (AQDS)/1,2‐benzoquinone‐3,5‐disulfonic acid (BQDS) RFBs. The device can be directly charged by solar light without external bias, and discharged like normal RFBs with an energy storage density of 1.15 Wh L−1 and a solar‐to‐output electricity efficiency (SOEE) of 1.7 % over many cycles. The concept exploits a previously undeveloped design connecting two major energy technologies and promises a general approach for storing solar energy electrochemically with high theoretical storage capacity and efficiency.

Integrated Photoelectrochemical Solar Energy Conversion and Organic Redox Flow Battery Devices.

Building on regenerative photoelectrochemical solar cells and emerging electrochemical redox flow batteries (RFBs), more efficient, scalable, compact, and cost-effective hybrid energy conversion and storage devices could be realized. An integrated photoelectrochemical solar energy conversion and electrochemical storage device is developed by integrating regenerative silicon solar cells and 9,10-anthraquinone-2,7-disulfonic acid (AQDS)/1,2-benzoquinone-3,5-disulfonic acid (BQDS) RFBs. The device can be directly charged by solar light without external bias, and discharged like normal RFBs with an energy storage density of 1.15 Wh L-1 and a solar-to-output electricity efficiency (SOEE) of 1.7 % over many cycles. The concept exploits a previously undeveloped design connecting two major energy technologies and promises a general approach for storing solar energy electrochemically with high theoretical storage capacity and efficiency.

Numerical algorithms based on Galerkin methods for the modeling of reactive interfaces in photoelectrochemical (PEC) solar cells

This work concerns the numerical solution of a coupled system of self-consistent reaction–drift–diffusion–Poisson equations that describes the macroscopic dynamics of charge transport in photoelectrochemical (PEC) solar cells with reactive semiconductor and electrolyte interfaces. We present three numerical algorithms, mainly based on a mixed finite element and a local discontinuous Galerkin method for spatial discretization, with carefully chosen numerical fluxes, and implicit–explicit time stepping techniques, for solving the time-dependent nonlinear systems of partial differential equations. We perform computational simulations under various model parameters to demonstrate the performance of the proposed numerical algorithms as well as the impact of these parameters on the solution to the model.

Rapid sintering of MoS2 counter electrode using near-infrared pulsed laser for use in highly efficient dye-sensitized solar cells

Abstract Molybdenum disulfide (MoS 2 ) is a promising material for use as a low-cost electrocatalytic counter electrode (CE) in photoelectrochemical dye-sensitized solar cells (DSSCs). However, currently, the MoS 2 CEs are generally prepared with a high temperature sintering for the synthesis and crystallization of MoS 2 . Here, we report a simple and rapid method for the preparation of highly efficient MoS 2 CEs. The MoS 2 films were synthesized at 70 °C, followed by sintering with a near-infrared (IR) pulsed laser for 1 min. Compared to the conventional heat-sintered MoS 2 CE, the laser-sintered CE showed enhanced crystallinity and improved interconnection between the MoS 2 particles, resulting in superior electrocatalytic activity towards the I − /I 3 − redox couple. When used in a DSSC, the laser-sintered MoS 2 CE exhibited a higher conversion efficiency ( η = 7.19%) compared to that of the heat-sintered CE ( η = 5.96%). Furthermore, the laser-sintered CE had a comparable conversion efficiency compared to that of the conventional Pt CE ( η = 7.42%).

Enhanced Photoelectrochemical Performance of Nanostructured Zinc Oxide Photoelectrodes Via Morphology Control

Photoelectrochemical solar cells (PEC) provide both harvesting and storage of the solar energy by converting it to chemical energy. In other words PEC systems convert sunlight into fuels by means of electrochemical reactions [1]. Total system efficiency of the PEC is directly affected by the performance of the working photoelectrode and the counter electrode. Here we investigated the influence of the morphology of the zinc oxide (ZnO) nanostructured photoelectrodes on the efficiency. ZnO photoelectrodes with nano-film, nanowire, and urchin-like morphologies have been used as working electrode in the three-electrode in one compartment cell configuration. Nano-films (ZnO-NF), 60 nm thick, have been deposited on the indium tin oxide (ITO) coated glass via physical vapor deposition. These films were used as the seeding layer to grow the ZnO nanowire arrays (ZnO-NW) by chemical bath deposition (CBD). Finally we fabricated the urchin-like nanostructures (ZnO-UL) on fluorine doped tin oxide coated (FTO) glass substrates by again CBD technique. In order to increase the coverage and the adhesion of the urchin-like structures we modified the surface of the FTO via hydroxylation process [2]. These electrodes were labeled as ZnO-H-UL. As expected, the light absorption of the nanowire and urchin-like structures was superior to the nanofilms. Therefore, nanowire formation slightly increased the current density under illumination at VAg/AgCl=0V bias. On the other hand, current density increased approximately 103 times and reached to 3 mA/cm2 for the ZnO-H-UL samples compare to the nano-films. Another drastic change was observed for the photoresponse, which is a measure of photo-generated current in the system. In other words photoresponse of the electrode can be calculated from the ratio of Jill-Jdark to Jdark, where Jill is the current density under illumination and Jdark is the current density at dark. The maximum photoresponse of the ZnO-NF was 4.5 indicating almost no current change in dark and under illumination. However, this value was 55, 7.9x102, and 1.2x103 for ZnO-NW, ZnO-UL and ZnO-H-UL electrodes, respectively. Enhancement in the photo generated current density for the urchin like structure could be related with the better light absorption and longer electron lifetime. According to our best knowledge this is the highest photoresponse reported in literature. Efficiency of the ZnO electrodes was calculated using the well known applied bias photon-to-current efficiency (ABPE) definition [3]. ABPE of the ZnO-NF and NW electrodes was 0.09 and 0.32 %, respectively. Efficiency of the ZnO electrodes increased with formation of needle like structures on the spherical bases. 0.65 and 0.87 % ABPE was observed for ZnO-UL and H-UL nanostructures, respectively. One can determine the overall PEC device efficiency by the ratio between the energy of the produced hydrogen and the total energy spent to accomplish the water splitting reaction [4]. PEC solar cells produced using ZnO-H-UL photoanode had the overall device efficiency of the 2.5%. Better photoresponse, photo current density, and the device efficiency of the ZnO-H-UL electrodes compare to the other nanostructures made them very favorable in PEC systems as working electrodes.

(Invited) Photoelectrochemical Water Splitting with Doped TiO2 Nanotube Arrays: Limits and Water Oxidation Efficiency

While solar energy is one of the few energy sources capable of meeting the world’s energy demands,1 the transient nature of sunlight necessitates the development of technologies to store that energy for on-demand use to supplement photovoltaics.2 Photoelectrochemical solar cells use sunlight to electrolyze water to produce hydrogen as an on-demand fuel, which can then be converted to electricity by a fuel cell. TiO2 nanotubes formed by the anodization of titanium foils in electrolytes containing fluoride ions produce aligned arrays of tube-like structures 70-100 nm in width and tunable length on the order of microns. These structures are a promising architecture for photoelectrochemical applications3 because of their high stability in solution and under irradiation, high surface area, and 1-dimensional charge transport for efficient movement of photogenerated charges. While hundreds of microns long nanotubes in principle may be grown, one major limitation on the performance of TiO2 nanotubes is the presence of defects in the crystal structure which facilitate the recombination of photogenerated electron-hole pairs;4 the best photoelectrochemical performance of TiO2 nanotubes for water splitting has been observed in Nb-doped TiO2 with a length of 7um and an associated photocurrent of 1.0 mA/cm2.5 Electrochemical H or Li doping was demonstrated to passivate the trap states in TiO2 nanotubes, suppressing recombination. This process resulted in up to a 2 fold increase in the photoelectrochemical performance of 1 um long TiO2 nanotubes compared to the undoped samples.6 For long TiO2 nanotubes, a new optimum length of 15 um was achieved, resulting in 1.5 mA/cm2 of photocurrent at 1.0 VSCE under simulated sunlight as seen in Figure 1(c). Photocurrent measurements with and without a hole scavenger did show a high efficiency towards water oxidation. These results demonstrate the ability to produce high performance TiO2 nanotubes for photoelectrochemical solar energy devices using simple electrochemical techniques. (1) Lewis, N. S.; Nocera, D. G. Proc. Natl. Acad. Sci. U. S. Amer. 2006, 103, 15729. (2) Cook, T. R.; Dogutan, D. K.; Reece, S. Y.; Surendranath, Y.; Teets, T. S.; Nocera, D. G. Chem. Rev. 2010, 110, 6474. (3) Tsui, L. -k.; Zangari, G. J. Electrochem. Soc. 2014, 161, D3066 (4) Tsui, L.; Zangari, G. Electrochim. Acta 2014, 121, 203. (5) Das, C.; Roy, P.; Yang, M.; Jha, H.; Schmuki, P. Nanoscale 2011, 3, 3094. (6) Tsui, L.; Saito, M.; Homma, T.; Zangari, G. J. Mater. Chem. A 2015, 3, 360.

(Invited) Si Photoelectrodes with Patterned Catalysts for Efficient and Stable Photoelectrochemical Solar Chemical Production

Solar fuel production using sun, CO2, and water at a semiconductor/water interface attracts intense interest for converting solar energy into storable and distributable chemicals. While numerous semiconductors have been investigated, a tandem cell comprised of semiconductors with two different bandgaps is considered one of the most promising candidates for realization of for unassisted efficient and stable solar chemical production. Si has a bandgap of 1.12 eV and can be used as an ideal bottom cell in a tandem configuration. Here, I’ll present our recent works on Si photoelectrodes with patterned co-catalysts for efficient and stable photoelectrochemical (PEC) solar chemical producing cells. In the first part of the presentation, I’ll talk about PEC properties of Si photoanode for oxygen evolution reaction with enhanced stability. Our Si photoanode is covered with chemically stable and electrically passivating SiO2 layer to prevent corrosion of Si in water. Since SiO2 is insulating, we locally pattern the oxide to expose Si surface and deposit Ni co-catalysts on the exposed Si. By controlling surface coverage of Ni co-catalysts, we achieve 27 mA/cm2 of oxygen evolving current density at 1.23 V (vs. RHE) for more than 24 hours. I'll present PEC device modeling of our Si photoelectrode structures. In the second part of talk, I’ll present Si photocathodes with nanoporous Au mesh for solar CO2 reduction reaction. Our Si photocathode with the nanoporous Au mesh shows CO2 reduction selectivity more than 90% at more positive potential than CO2/CO redox potential. In the presentation, PEC performance of our Si electrode will be presented in detail.

(Invited) Photocurrent Spectroscopy in Corrosion and Passivity Studies: A Critical Assessment

Photocurrent Spectroscopy (PCS) is currently employed for the characterization of solid-state properties of semiconducting and insulating materials, since the knowledge of their band gap is a prerequisite to any possible application in different fields such as: solar energy conversion (photoelectrochemical and photovoltaic solar cells, photocatalysis) and microelectronics (high-k, high band-gap materials) (1-2). In the last 20-30 years an increasing number of scientists working in the area of corrosion has been attracted by this technique owing to its versatility and ability to scrutinize in situ corrosion layers and passive films having semiconducting or insulating behaviour. In previous works (3-4) we have shown that PCS is able to provide detailed information on characteristic energy levels of passive film/electrolyte junctions (flat band potential: Ufb; internal photoemission threshold: Eth; band gap value: Eg), which control the mechanism of charge transfer (electrons and ions) at the metal/corrosion layer/ electrolyte interface. Further advantages stem out from the fact that PCS does not require particular surface finishing control and can be used both in large area as well as in microscopic region of the electrode, and can reach high sensitivity by using a lock-in amplifier coupled to a mechanical light chopper. According to this, numerous experimental studies have shown how it is possible to scrutinize corrosion layer and passive films of very limited thickness grown on metals and alloys (Fe, Cr, Ni and SS) of relevant industrial interest (3-4 and refs. therein). In an attempt to make more quantitative the characterization of corrosion layer and passive by PCS, in previous works (3-4) we have shown that it is possible to correlate semi-empirically the band gap values of numerous binary oxides to their composition by using the Pauling’s equation for the average bond energy, i.e.: Eg =2[EI(χM -χO)2 +Ξ] (1) where χM and χO are the electronegativities, in the Pauling’s scale, of metal and oxygen respectively, and the remaining terms have been defined in the original work (5). Apart few noticeably exceptions, eq. (1) assumed, for sp-metal and d-metal oxides the following expression: Eg - ΔEam (eV) = 2.17(χM−χO)2 − 2.71 for sp metal (1b) Eg - ΔEam(eV) = 1.35(χM −χO)2 − 1.49 for d metal (1c) where ΔEam = 0 for crystalline oxides, whilst increasing ΔEam values have been suggested with a decreasing crystallinity degree. Moreover in several successive works (see refs. in 3-4), we have been able to show that in the case of ternary oxides by using of an average electronegativity parameter defined as the atomic % average between electronegativities of partner metals, eqs. (1b) and (1c) were able to correlate the band gap values measured by PCS with the mixed oxide composition. In this work, in order to test the validity of eq.1 for ternary oxides, we will carry out a comparison between several experimental Eg values of ternary oxides and the Eg values obtained by using eq.1 with the average electronegativity value for ternary oxide given by: χav = x1χcat1 + x2χcat2 where χ cat1,cat2 and x1,2 are the electronegativity parameter and atomic fraction of cations 1,2 in the ternary oxides, respectively. Moreover, some very recently publishes Eg values of mixed d-d metal oxides, of large interest in corrosion studies, theoretically derived from Density Functional Theory will be compared with PCS measured data and with those estimated according to eq. (1). Possible explanations of the difference in experimental and theoretical data will be presented and discussed. References 1- L. Peter, in "Comprehensive Chemical Kinetics", vol.29, p.382, Ed. by R.G. Compton, Elsevier Science, Oxford (1989). 2- V. Afanas'ev, A. Stesmans, Andre, Journal of Applied Physics, 102 (2007) 1 3- F. Di Quarto, M. Santamaria, and C. Sunseri, in “Analytical Methods in Corrosion Science and Technology”, P. Marcus and F. Mansfeld, Editors, p. 697, Taylor and Francis, Boca Raton, FL (2005) 4- F. Di Quarto, F. La Mantia, M. Santamaria, in "Modern Aspects of Electrochemistry, No. 46: Progress in Corrosion Science and Engineering I", Ed. by Su-Il Pyun and Jomg-Won Lee, Ch. 4, p. 231, New York: Springer (UNITED STATES), 2009. 5- F. Di Quarto, C. Sunseri, S. Piazza, M.C. Romano, J.Phys. Chem. B, 101, 2519 (1997)

Copper Indium Sulfide Photoelectrode Design for Solar Water Splitting

There is a considerable interest in copper based chalcopyrite thin films for photoelectrochemical (PEC) water-splitting due to their high absorption coefficient and tunable band gap. Among the other chalcopyrite semiconductor materials various advantages of copper indium sulfide (CuInS2) thin films made them favorable in photovoltaic applications as well as in solar water splitting. First CuInS2 thin films can be deposited on various substrates via cost effective methods including solution-based manufacturing. Second the control of structure and the properties of CuInS2 thin films are easier than that of quaternary chalcopyrite films like copper indium gallium sulfide/selenide. At last but not least, it is possible to produce fully green manufacturing of CuInS2 thin films unlike selenium containing compounds. In this work, spray pyrolysis technique has been used to manufacture CuInS2 based electrodes. Spray pyrolysis is a facile way to produce thin films over large areas using very little amount of solution. High throughput of this technique is especially important for the deposition of rare materials like indium. More specifically, here we used only 0.75 ml of precursor solution per cm2 to build 1 micrometer thick CuInS2 films, which is the lowest solution amount reported in literature. CuInS2, CuInS2/In2S3 and ZnO-nanowire/CuInS2 heterojunctions on indium tin oxide (ITO) coated glass have been studied as the photocathode for solar water splitting. The maximum current density observed under illumination and therefore the maximum photoconversion efficiency of the CuInS2 electrodes has been affected by the precursor solution. In other words stoichiometry of the films were important to enhance the electron transfer from the CuInS2 to the conduction band of ITO. It has been observed that Cu/In and S/(Cu+In) ratios directly affected the photoelectrochemical performance. As a general trend the applied bias photon-to-current efficiency (ABPE) increased with increasing the S/(Cu+In) ratio. Besides the maximum performance of the spray pyrolyzed CuInS2 electrodes were observed for Cu/In=1.3. Although the efficiencies of the CuInS2 photocathodes reached to 6.6 %, photosensitivity of the electrodes was poor. The maximum efficiency for CuInS2 electrodes calculated using the differences between dark and illuminated current density, which is called as photo current density (Jphoto), was 0.53%. Therefore, indium sulfide (In2S3) thin films have been deposited on CuInS2 electrodes via again spray pyrolysis. The photosensitiy and the stability of the CuInS2 photocathodes were increased with In2S3 deposition. The maximum efficiency calculated using Jphoto was about 0.93% for the CuInS2/In2S3 all-spray-deposited electrodes. Finally we fabricated ZnO-nanowire/CuInS2 heterojunctions to improve the sensitivity and absorption. Nanowire arrays provided better electron transport and hence enhanced performance. The efficiency of the photocathodes increased more than five times compare to the flat electrode designs of CuInS2. The maximum efficiency of 2.8% has been observed for the ZnO-nanowire/CuInS2 heterojunction electrodes. This value is very promising to utilize them into low cost and efficient photoelectrochemical solar cells as photocathode.

Hydropowered photoelectrochemical water splitting solar cell for hydrogen production

Photoelectrochemical (PEC) water splitting has been considered to be a promising route for sustainable hydrogen production from the solar energy. However, owing to the suitable potential required for such process, the external bias is usually indispensable on the PEC cell, which hinders its wide application. In this paper, we integrated the PEC cell with hydroelectric generator for water splitting, where the bias potential of the PEC was supplied from its water environment. The ZnO and TiO2 films were prepared on conductive FTO substrates for photoanodes by magnetron sputtering and atomic layer deposition, respectively, while structures and morphologies of the films were characterized by XRD and AFM. A three-electrode electrochemical cell configuration was performed to measure the PEC performance. The results demonstrate that PEC performance can be effectively facilitated when the PEC cell was connected with the hydroelectric generator, which suggests a promising route toward full green design for hydrogen production.

Dye sensitized solar cell based on TiO2 nanoparticles and chlorophyll from Pandanus amaryllifolius Roxb. leaves

Dye sensitized solar cell (DSSC) is a low-cost photo electrochemical solar cell, that belongs to third generation solar cells and known for its easy fabrication procedures. Its working is based on the interfacial kinetics between a photo-sensitized nanocryastalline anode and an electrolyte, with a counter electrode to complete the cell configuration. A lot of research has been conducted due to their interesting potential for low-cost, lightweight, with reasonably good photovoltaic efficiency. Present work reports the dye sensitized solar cells using TiO2 nanoparticles with Pandanus amaryllifolius chlorophyll as an absorber. P. amaryllifolius leaves are rich in chlorophyll and widely used as natural colorant to impart deep green colour to food products. Moreover, the leaves are rich in basmati aroma volatiles. In the present investigation, chlorophyll pigment was extracted from P. amaryllifolius leaves and nanocrystalline Titanium dioxide (TiO2) film was prepared by doctor blade method. The Titania films were immersed overnight in the chlorophyll extract for sensitization. An electrolyte solution consisting of Polyiodide was injected into the cell before sealing it. Pt coated FTO was used as counter electrode to assemble the cell configuration before it was characterized for its photovoltaic performance. The photoelectrochemical performance of the fabricated DSSC based on this dye showed 0.14 mA/cm2 short circuit current (JSC) and 0.125 V open circuit voltage (VOC).

Photoelectrochemical characteristics, photodegradation and kinetics of metal and non-metal elements co-doped photocatalyst for pollution removal

Considering coordination effects, this study prepared a photocatalyst with a highly visible light respondence using co-doped titania with non-metal (nitrogen and sulfur) and lanthanide metal ions (cerium). As well, the photoelectrochemical characteristics and photocatalytic effects were tested. The feasibility was investigated on the power of the photoelectrochemical solar cell and the photodegradation of volatile organic compounds (VOCs) from indoor air pollution, taking toluene as a model compound. In this study, the different intensities of a light-emitting diode (LED) and the different initial concentrations (10–50ppmv) were examined, and the kinetic model was addressed. The maximum power (Pm) at white light emitting diode (WLED) was 35.5 and 174.68times that of the solar cell without cerium doping and without Ce, N and S doping, respectively. The decomposition efficiency (ηD) was more than 99.9% below 30ppmv at 5050WLED with 10Ce/TiNxSyO2−x−y (10Ce/TNST). The photocatalytic decomposition was elucidated according to the Langmuir-Hinshelwood model. The reaction rate constant (k) and adsorption equilibrium constant (KL) of 10Ce/TNST with 5050WLED in the range of 10–50ppmv were 0.2637ppmvmin−1 and 0.7008ppmv−1, respectively. This study succeeded in predicting optimum photodegradation conditions from the PECSC test. The photocurrent and power from the co-doped photocatalysts are related to the photodegradation efficiency.

Novel CuIn1-xGaxTe2Structures for High Efficiency Photo-electrochemical Solar Cells

Novel CuIn1-xGaxTe2Structures for High Efficiency Photo-electrochemical Solar Cells

Synthesis of SnS2 thin film via non vacuum arrested precipitation technique for solar cell application

In the current status, we have successfully synthesized SnS2 thin film by using economically cheap and non vacuum arrested precipitation technique (APT) for photoelectrochemical (PEC) solar cell application for the first time. The X-ray diffraction (XRD) pattern confirms the formation of pure hexagonal crystal structure. Scanning electron microscopy (SEM) micrographs illustrate the formation of spherical surface morphology with homogeneous coverage of substrate surface. PEC study demonstrates 0.0023 % conversion efficiency.

Inorganic p-Type Semiconductors: Their Applications and Progress in Dye-Sensitized Solar Cells and Perovskite Solar Cells

Considering the increasing global demand for energy and the harmful ecological impact of conventional energy sources, it is obvious that development of clean and renewable energy is a necessity. Since the Sun is our only external energy source, harnessing its energy, which is clean, non-hazardous and infinite, satisfies the main objectives of all alternative energy strategies. With attractive features, i.e., good performance, low-cost potential, simple processibility, a wide range of applications from portable power generation to power-windows, photoelectrochemical solar cells like dye-sensitized solar cells (DSCs) represent one of the promising methods for future large-scale power production directly from sunlight. While the sensitization of n-type semiconductors (n-SC) has been intensively studied, the use of p-type semiconductor (p-SC), e.g., the sensitization of wide bandgap p-SC and hole transport materials with p-SC have also been attracting great attention. Recently, it has been proved that the p-type inorganic semiconductor as a charge selective material or a charge transport material in organometallic lead halide perovskite solar cells (PSCs) shows a significant impact on solar cell performance. Therefore the study of p-type semiconductors is important to rationally design efficient DSCs and PSCs. In this review, recent published works on p-type DSCs and PSCs incorporated with an inorganic p-type semiconductor and our perspectives on this topic are discussed.

Electronic and chemical structure of the H2O/GaN(0001) interface under ambient conditions.

We employed ambient pressure X-ray photoelectron spectroscopy to investigate the electronic and chemical properties of the H2O/GaN(0001) interface under elevated pressures and/or temperatures. A pristine GaN(0001) surface exhibited upward band bending, which was partially flattened when exposed to H2O at room temperature. However, the GaN surface work function was slightly reduced due to the adsorption of molecular H2O and its dissociation products. At elevated temperatures, a negative charge generated on the surface by a vigorous H2O/GaN interfacial chemistry induced an increase in both the surface work function and upward band bending. We tracked the dissociative adsorption of H2O onto the GaN(0001) surface by recording the core-level photoemission spectra and obtained the electronic and chemical properties at the H2O/GaN interface under operando conditions. Our results suggest a strong correlation between the electronic and chemical properties of the material surface, and we expect that their evolutions lead to significantly different properties at the electrolyte/electrode interface in a photoelectrochemical solar cell.