首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 515 毫秒
1.
In this paper, we report a novel CdS and PbS quantum dots (QDs) co-sensitized TiO2 nanorod arrays photoelectrode for quantum dots sensitized solar cells (QDSSCs). TiO2 film consisting of free-standing single crystal nanorods with several microns high and 90–100 nm in diameter were deposited on a conducting glass (SnO2:FTO) substrate by hydrothermal method. Then CdS/PbS QDs were deposited in turn on TiO2 nanorods by facile SILAR technique. The FTO/TiO2/CdS/PbS, used as photoelectrode in QDSSCs, produced a light to electric power conversion efficiency (Eff) of 2.0% under AM 1.5 illumination (100% sun), which shows the best power conversion efficiency compared with single CdS or PbS sensitized QDSSCs. One dimension TiO2 nanorod provides continuous charge carrier transport pathways without dead ends. The stepwise structure of the band edges favored the electron injection and the hole-recovery for both CdS and PbS layers in photoelectrode, which may gave a high electric power conversion efficiency. The facile preparation and low cost nature of the proposed method and structure make it has a bright application prospects in photovoltaic areas in the future.  相似文献   

2.
Titanium dioxide thin films were deposited by filtered cathodic arc evaporation (FCAE) from a Ti target in an oxygen atmosphere onto (a) fluorine-doped tin oxide substrates SnO2:F (FTO) and (b) glass microscope slides. The growth rate calculated from film thickness profilometry measurements was found to be approximately 0.8?nm/s. The films were highly transparent to visible light. x-Ray photoemission spectroscopy analysis of the Ti 2p electron binding- energy shift confirmed the presence of a TiO2 stoichiometric compound. The results for the root-mean-square (RMS) surface roughness of the films deposited onto FTO substrates evaluated by atomic force microscopy suggested nanostructured film surfaces. When exposed to hydrogen plasma, TiO2 films revealed insignificant changes in the optical spectra. The initial sheet resistance of the SnO2:F layer was 14?Ω/sq. The deposition of the top TiO2 layer (45?nm thick) over the FTO electrode resulted in an increase of the sheet resistance of 2?Ω/sq. In addition, the sheet resistance of the double-layer FTO/TiO2 transparent conductive oxide (TCO) electrode increased by 1?Ω/sq as a result of H+ plasma exposure. Regardless of the TiO2 film’s low conductivity, a thin protective layer could be coated onto FTO films (presumably 15?nm thick) due to their high transparency, offering high resistance to aggressive H+ plasma conditions. In this paper we show that ~50-nm-thick TiO2 coating on FTO films provides sufficient protection against deterioration of transparency and conductivity due to hydrogen radical exposure.  相似文献   

3.
In the present work, CdS nanoparticles as a sensitizer were grown on the spin coated nanoporous TiO2 film by repeated cycles of a Successive Ionic Layer Adsorption and Reaction (SILAR) method. ZnS layer was coated on the CdS/TiO2 anodes to act as a protection layer on CdS. The crystallite size of CdS nanocrystals is calculated to be 3 nm from XRD spectra. The optical band gap of the film determined from transmittance spectra decreases from 3.46 to 2.15 eV with the increase in the number of CdS SILAR cycles. SEM and TEM analysis depict the enabled penetration of CdS (1 1 1) nanoparticles into the nanoporous TiO2 (1 0 1) structure. EDX study confirms the presence of all the elements (Ti, Cd, S, Zn and O) found on the photoanode. The attachment of cubic structured CdS on anatase phase of TiO2 in the photoanode is verified using Raman spectra. Photoluminescence (PL) study shows that the emission peak corresponding to TiO2 has been slightly blueshifted due to the interaction of CdS nanoparticles in TiO2 nanoporous structures. The electrical measurement shows that the dark and light illuminated resistivity of the preferred photoanode is 7.91 and 5.65 Ω cm respectively.  相似文献   

4.
Based on the normal pulsed laser ablation method,femtosecond pulsed laser deposition(fs-PLD)is adopted in vacuum for the production of TiO2nanoparticle-assembled films.We study the morphology and electronic characteristics of TiO2nanoparticle-assembled films deposited at different oxygen background gas pressures from high vacuum(~10-4Pa)to 100 Pa and different deposition time.Our results show that TiO2nanoparticle-assembled films obtained in high vacuum present both a mixture with rutile phase and anatase phase and a pure rutile phase.At the same time,there are more mesoporous structures in the film after annealing,which is beneficial for the enhancement of photocatalytic activity.In water splitting experiment,part of the TiO2nanoparticle-assembled films embedded with a small mass fraction of CdS nanoparticles(~5%)present an interesting photocurrent enhancement with a maximum value of~0.2mA/cm2under a solar simulator.  相似文献   

5.
TiO2 nanotube arrays and particulate films are modified with CdS quantum dots with an aim to tune the response of the photoelectrochemical cell in the visible region. The method of successive ionic layer adsorption and reaction facilitates size control of CdS quantum dots. These CdS nanocrystals, upon excitation with visible light, inject electrons into the TiO2 nanotubes and particles and thus enable their use as photosensitive electrodes. Maximum incident photon to charge carrier efficiency (IPCE) values of 55% and 26% are observed for CdS sensitized TiO2 nanotube and nanoparticulate architectures respectively. The nearly doubling of IPCE observed with the TiO2 nanotube architecture is attributed to the increased efficiency of charge separation and transport of electrons.  相似文献   

6.
TiO2 nanorod arrays (NRAs) were prepared on fluorine doped tin oxide (FTO) substrates by a facile two-step hydrothermal method. The nanorods were selectively grown on the FTO regions which were covered with TiO2 seeding layer. It took 5 h to obtain the compact arrays with the nanorod length of ~2 μm and diameter of ~50 nm. The photoelectrochemical (PEC) properties of TiO2 NRAs are also investigated. It is demonstrated that the TiO2 NRAs indicate the good photoelectric conversion ability with an efficiency of 0.22% at a full-wavelength irradiation. A photocurrent density of 0.21 mA/cm2 is observed at 0.7 V versus the saturated calomel electrode (SCE). More evidences suggest that the charge transferring resistance is lowered at an irradiation, while the flat-band potential (Vfb) is shifted towards the positive side.  相似文献   

7.
TiO2 nanotubes were prepared by hydrothermal treatment of TiO2 powder in NaOH aqueous solution and then calcined at various temperatures. The post-calcination treated TiO2 nanotubes were decorated with CdS by wetness impregnation and subsequently sulfurization to fabricate CdS/TiO2 composites. The photocatalytic performance of CdS/TiO2 composites toward hydrogen production from water splitting was investigated. The results show that the calcination temperature of TiO2 nanotubes has a significant effect on the photocatalytic performance of CdS/TiO2. With the increase of calcination temperature from 300 to 500 °C, the crystallinity of TiO2 nanotubes is increased resulting in the enhanced photocatalytic performance of CdS/TiO2. When the calcination temperature is higher than 500 °C, TiO2 nanotubes gradually transform into nanorods and finally completely collapse, which leads to the decrease of photocatalytic performance of CdS/TiO2. The CdS/TiO2 composite with TiO2 nanotubes calcined at 500 °C exhibits the highest hydrogen evolution rate, which could be attributed to its 1 D nanotubular structure and good crystallinity.  相似文献   

8.
A composition of CdS nanoparticles and nanowires were deposited on TiO2 nanorods by successive ionic layer adsorption and reaction method grown on Ti substrate. CdS/TiO2/Ti device were used as photoanode in solar cell. Efficiency, short circuit current, and open circuit voltage were measured. Also, electron life time in each Fermi level and order of recombination were obtained by open circuit voltage decay and short circuit photocurrent interrupt voltage; respectively. Our results showed that there is an optimum composition of CdS nanoparticles and nanowires which improves solar cell properties of this type of cell.  相似文献   

9.
Lead sulfide (PbS) and cadmium sulfide (CdS) quantum dots (QDs) are prepared over mesoporous TiO2 films by a successive ionic layer adsorption and reaction (SILAR) process. These QDs are exploited as a sensitizer in solid‐state solar cells with 2,2′,7,7′‐tetrakis(N,N‐di‐p‐methoxyphenylamine)‐9,9′‐spirobifluorene (spiro‐OMeTAD) as a hole conductor. High‐resolution transmission electron microscopy (TEM) images reveal that PbS QDs of around 3 nm in size are distributed homogeneously over the TiO2 surface and are well separated from each other if prepared under common SILAR deposition conditions. The pore size of the TiO2 films and the deposition medium are found to be very critical in determining the overall performance of the solid‐state QD cells. By incorporating promising inorganic QDs (PbS) and an organic hole conductor spiro‐OMeTAD into the solid‐state cells, it is possible to attain an efficiency of over 1% for PbS‐sensitized solid‐state cells after some optimizations. The optimized deposition cycle of the SILAR process for PbS QDs has also been confirmed by transient spectroscopic studies on the hole generation of spiro‐OMeTAD. In addition, it is established that the PbS QD layer plays a role in mediating the interfacial recombination between the spiro‐OMeTAD+ cation and the TiO2 conduction band electron, and that the lifetime of these species can change by around 2 orders of magnitude by varying the number of SILAR cycles used. When a near infrared (NIR)‐absorbing zinc carboxyphthalocyanine dye (TT1) is added on top of the PbS‐sensitized electrode to obtain a panchromatic response, two signals from each component are observed, which results in an improved efficiency. In particular, when a CdS‐sensitized electrode is first prepared, and then co‐sensitized with a squarine dye (SQ1), the resulting color change is clearly an addition of each component and the overall efficiencies are also added in a more synergistic way than those in PbS/TT1‐modified cells because of favorable charge‐transfer energetics.  相似文献   

10.
Residual CdCl2 in chemical bath deposited (CBD) CdS layer was utilized to observe grain growth in CdTe layer for glass/SnO2/CBD-CdS/CdTe structures. The above as-deposited composite films were subjected to rapid thermal annealing (RTA) for observing grain growth and subsequent cell fabrication. The films were characterized by studying their microstructural and compositional properties. Interfacial mixing behavior was studied by secondary ion mass spectroscopy (SIMS) measurements which showed a slight interfacial diffusion of the CdS layer into the CdTe layer. Performance of a photovoltaic (PV) cell structure with non-optimized thickness of the CdTe and CdS layers obtained by this technique was studied. Carrier life time was obtained from Voc decay measurement. Photoinduced charge separation observed in this glass/SnO2/CBD–CdS/CdTe structure was associated with an increase in the dielectric constant and a decrease in the device resistance.  相似文献   

11.
Efficient charge separation and transport as well as high light absorption are key factors that determine the efficiency of photoelectrochemical (PEC) water splitting devices. Here, a PEC device consisting of a hematite nanoporous film deposited on Pt nanopillars, followed by the decoration with an Fe2TiO5 passivation layer, is designed and fabricated. This structure can largely improve the light absorption in the composite materials, and significantly enhance the water oxidation performance of hematite photoanodes. The Fe2TiO5 thin shell and Pt underlayer significantly improve the interfacial charge transfer while minimizing the hole‐migration length in Fe2O3 photoanodes, leading to a drastically increased photocurrent density. Specially, the Fe2TiO5/Fe2O3/Pt photoanode yields an excellent photoresponse for PEC water splitting reactions with 1.0 and 2.4 mA cm?2 obtained at 1.23 and 1.6 VRHE under AM 1.5G illumination in 1 m KOH. The resulting photocurrents are 2.5 times enhanced compared to a pristine Fe2O3 photoanode of the same geometry. These results demonstrate a synergistic charge transfer effect of Fe2TiO5 and Pt layers on hematite for the improvement of PEC water oxidation.  相似文献   

12.
A novel scaffold layer composed of TiO2-ZrO2 composite was fabricated for perovskite solar cell. Compared with pure TiO2 nanoparticles (NPs), the relatively larger ZrO2 NPs could increase film roughness and enhance light-scattering effect in TiO2-ZrO2 composite films. The device exhibited outstanding power conversion efficiency (PCE) of 11.41%. The morphology and aggregation of particles, three-dimensional roughness, as well as the ingredient and micro-structure of FTO/compact TiO2/TiO2-ZrO2 was investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscope (AFM), energy dispersive spectrometer (EDS), and X-ray diffraction (XRD), respectively. Moreover, the optical property of TiO2-ZrO2 films for visible light was characterized by UV–visible absorption spectroscopy (UV–vis), and its influence on quantum yield of the device was further demonstrated by incident photon-to-electron conversion efficiency (IPCE). Owing to the inert oxide, the short-circuit current density of perovskite solar cell using TiO2-ZrO2 composition as scaffold layer increased by 21% compared to the one employing pure TiO2 mesoporous film.  相似文献   

13.
The feasibility of measuring contact wetting angles to characterize processing induced changes to thin film semiconductors in CdTe/CdS solar cells is evaluated. The contact angles of water and formamide are used to determine the polar and dispersive surface energies of the thin films using two analysis methods. Changes in surface energies resulting from processing are correlated to changes in surface chemistry and structure detected by glancing incidence X‐ray diffraction (GIXRD), X‐ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). Surface energies are evaluated for sputtered In2O3:SnO2, chemical surface‐deposited CdS, and physical vapor‐deposited (PVD) CdTe thin films under as‐deposited and treated conditions. Treatments include thermal anneal in air, argon, and CdCl2 ambient as well as surface etching. Indium tin oxide (ITO) and CdS films exhibit increased polar surface energy corresponding to enhanced crystallization of surfaces resulting from processing and increasing CdS growth temperature. Native oxidation of PVD CdTe (111)‐oriented film surfaces occurs rapidly and is readily detected by changes in contact angle. Surface energies of PVD (111)‐oriented CdTe stored under various humidities prior to processing are energetically similar due to native oxidation. The polar energy of CdTe surfaces is affected by the addition or removal of crystalline surface oxides during film processing. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

14.
Cadmium sulfide (CdS) thin films were deposited onto soda lime glasses and p-Si semiconductors at various substrate temperatures (40, 150 and 275 °C) by radio frequency (RF) sputtering technique. The effect of substrate temperature on morphological, structural and optical properties of CdS thin films were analyzed by means of atomic force microscopy (AFM), x-ray diffraction (XRD) and uv–vis spectrum data. The results showed that the average roughness (Ra) of thin films increased from 2.0 to 4.0 nm and all films had hexagonal wurtzite structure. The optical band gaps of CdS thin films varied between 2.46–2.43 eV. Characteristic parameters of CdS/p-Si heterojunctions including ideality factor, barrier height, series resistance and rectification ratio were measured. It was seen that both ideality factor and barrier height values of the heterojunctions increase with the increase substrate temperature. It was attributed to increase in inhomogenity of the thin films. Furthermore, the photoelectrical parameters of CdS/p-Si heterojunctions were studied.  相似文献   

15.
CdS thin films are a promising electron transport layer in PbS colloidal quantum dot (CQD) photovoltaic devices. Some traditional deposition techniques, such as chemical bath deposition and RF (radio frequency) magnetron sputtering, have been employed to fabricate CdS films and CdS/PbS CQD heterojunction photovoltaic devices. However, their power conversion efficiencies (PCEs) are moderate compared with ZnO/PbS and TiO2/PbS heterojunction CQD solar cells. Here, efficiencies have been improved substantially by employing solution‐processed CdS thin films from a single‐source precursor. The CdS film is deposited by a straightforward spin‐coating and annealing process, which is a simple, low‐cost, and high‐material‐usage fabrication process compared to chemical bath deposition and RF magnetron sputtering. The best CdS/PbS CQD heterojunction solar cell is fabricated using an optimized deposition and air‐annealing process achieved over 8% PCE, demonstrating the great potential of CdS thin films fabricated by the single‐source precursor for PbS CQDs solar cells.  相似文献   

16.
A novel hierarchical structured photoanode based on metal–organic frameworks (MOFs)‐derived porous Co3O4‐modified TiO2 nanorod array grown on Si (MOFs‐derived Co3O4/TiO2/Si) is developed as photoanode for efficiently photoelectrochemical (PEC) water oxidation. The ternary Co3O4/TiO2/Si heterojunction displays enhanced carrier separation performance and electron injection efficiency. In the ternary system, an abnormal type‐II heterojunction between TiO2 and Si is introduced, because the conduction band and valence band position of Si are higher than those of TiO2, the photogenerated electrons from TiO2 will rapidly recombine with the photogenerated holes from Si, thus leading to an efficient separation of photogenerated electrons from Si/holes from TiO2 at the TiO2/Si interface, greatly improving the separation efficiency of photogenerated hole within TiO2 and enhances the photogenerated electron injection efficiency in Si. While the MOFs‐derived Co3O4 obviously improves the optical‐response performance and surface water oxidation kinetics due to the large specific surface area and porous channel structure. Compared with MOFs‐derived Co3O4/TiO2/FTO photoanode, the synergistic function in the MOFs‐derived Co3O4/TiO2/Si NR photoanode brings greatly enhanced photoconversion efficiency of 0.54% (1.04 V vs reversible hydrogen electrode) and photocurrent density of 2.71 mA cm?2 in alkaline electrolyte. This work provides promising methods for constructing high‐performance PEC water splitting photoanode based on MOFs‐derived materials.  相似文献   

17.
Multiwalled carbon nanotube/TiO2 multilayer nanocomposite was successfully deposited on the fluorine-doped tin oxide (FTO) glass via layer-by-layer assembly technique to modify interfacial contact between the FTO surface and nanocrystalline TiO2 layer as well as carbon nanotube/TiO2 contacts in photoanode of dye sensitized solar cell. Using this approach, binder-free interfacial thin film was developed with nonagglomerated, well-dispersed MWCNTs on FTO and into TiO2 matrix and with maximum covering of TiO2 nanoparticles on MWCNTs. Introduction of MWCNTs/TiO2 interfacial layer into the TiO2 photoanode increased short circuit current density (Jsc) from 11.90 to 17.25 mA/cm2 and open circuit voltage (Voc) from 730 mV to 755 mV, whereas there was no notable change in the fill factor (FF). Consequently, power conversion efficiency (η) was enhanced from 5.32% to 7.53%, yielding a 41.5% enhancement. The results suggest that our simple strategy can integrate reduction of back electron reaction at FTO/TiO2 interface with the effective charge transport ability of carbon nanotubes and possessing high surface area for efficient dye loading.  相似文献   

18.
The CdS:Cl thin films have been prepared using thermally evaporated, CdCl2-mixed CdS powder at 200°C substrate temperature. The percentage of CdCl2 in the mixture varied from 0% to 0.20%. The electrical properties and the grain size of the deposited films were investigated. The results show that light doping, resistivity, carrier concentration, and mobility follow Seto’s model for polycrystalline material. However, with heavy doping, these properties undergo a saturation trend. The saturation behavior can be understood in terms of the rapid formation of the A-center complexes in the films. The deposited films were annealed at 250°C and 300°C. The resistivity of pure and lightly doped CdS films increased with annealing temperature, whereas carrier concentration and mobility in these films decreased. However, for the higher doping concentrations, the resistivity decreased, whereas carrier concentration and mobility showed improvement. These changes in electrical properties of the deposited films with annealing and doping concentration are attributed to a reduction in the lattice defect sites in CdS upon annealing. The experimental results are interpreted in terms of a modified version of Seto’s model for polycrystalline materials.  相似文献   

19.
CdS is a promising visible light response photoanode of photoelectrochemical (PEC) water splitting, but it remains a great challenge for practical application, due to the photohole‐induced self‐corrosion, and sulfide/sulfite ions as hole scavengers are always necessary for stable solar hydrogen generation. Herein, a CdS/SnSx nanorods/nanosheets hierarchical heterostructure with novel phase‐engineered band alignment is rationally designed via a two‐step solution reaction route for PEC water splitting. In the Na2SO4 aqueous electrolyte without any hole scavengers, compared with the pristine CdS, the CdS/SnSx photoanode achieves a remarkably enhanced photocurrent density of 1.59 mA cm?2 and a considerable stability at bias potential 1.23 V versus reversible hydrogen electrode (RHE) under simulated sunlight. It is proposed that the deposited SnSx nanosheets not only act as protective layers to restrain the photocorrosion of CdS, but also facilitate the charge separation in CdS by the virtue of the Type II heterojunction formed between CdS and SnSx.  相似文献   

20.
In this research, TiO2 thin films prepared via thermal oxidation of Ti layers were deposited by RF-magnetron sputtering method at three different sputtering powers. The effects of sputtering power on structure, surface and optical properties of TiO2 thin films grown on glass substrate were studied by X-ray diffraction (XRD), atomic force microscopic (AFM) and UV–visible spectrophotometer. The results reveal that, the structure of layers is changed from amorphous to crystalline at anatase phase by thermal oxidation of deposited Ti layers and rutile phase is formed when sputtering power is increased. The optical parameters: absorption coefficient, dielectric constants, extinction coefficient, refractive index, optical conductivity and dissipation factor are decreased with increase in sputtering power, but increase in optical band gap is observed. The roughness of thin films surface is affected by changes in sputtering power which is obtained by AFM images.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号