ZnS Photoanode Research Articles

Design strategy of TiO2/AgInSe/CdS/CdSe/ZnS photoanode and optimization of CdSe nanoparticles layer for increasing the efficiency of quantum dot-sensitized solar cells

In this study, ternary AgInSe (AISe) quantum dots compound were synthesized using a novel chemical precipitation method followed by a controlled hydrothermal treatment. The as-prepared particles were deposited onto a mesoporous TiO2 substrate to be applied as the photoelectrode of quantum dot sensitized solar cells (QDSSCs). Two configurations of multilayer photoanodes i.e. the TiO2 NCs/AgInSe/CdS/ZnS and TiO2 NCs/AgInSe/CdS/CdSe/ZnS were fabricated and employed for higher photovoltaic performance. The co-sensitizing CdS and CdSe nanocrystals layers were synthesized and deposited through successive ionic layer adsorption and reaction (SILAR) and chemical bath deposition (CBD) techniques, respectively. The results revealed that the QDSSCs with TiO2 NCs/AgInSe/ZnS photoanode initially showed an efficiency of 0.45 %. Incorporating CdS NCs as a quasi-shell film increased the efficiency to 3.9 % in the optimized TiO2/AgInSe/CdS(3 cycle)/ZnS configuration. Adding CdSe nanocrystals over-layer did not improve the efficiency of corresponding cells due to the increased thickness and resistance. Instead, the TiO2/AgInSe/CdS(2 cycle)/CdSe(12 min)/ZnS photoanode resulted in the efficiency of 4.10 % with 34 % improvement. Using the sub-micron size TiO2 hollow spheres (HSs) as the light scattering layer created further light absorption and enhanced performance. It was shown that the photovoltaic parameters were increased to short circuit current density (Jsc) of 23.25 mA/cm2, open-circuit voltage (Voc) of 512 mV and overall efficiency equal to 4.55 %

Facile fabrication of quantum dot–sensitized solar cells with multilayer TiO2 NCs/TiO2 HSs/CIS/CdS/CdSe(Xmin)/ZnS photoanode and modification of light scattering and co-sensitization for higher efficiencies

Facile fabrication of quantum dot–sensitized solar cells with multilayer TiO2 NCs/TiO2 HSs/CIS/CdS/CdSe(Xmin)/ZnS photoanode and modification of light scattering and co-sensitization for higher efficiencies

Mn-doped ZnS nanoparticle photoanodes: Synthesis, structural, optical, and photoelectrochemical characteristics

In this work, Mn-doped zinc sulfide (Mn:ZnS) nanoparticles (NPs) have been synthesized as a promising material for photoelectrochemical water splitting (PEC), using the co-precipitation method. PEC properties of Mn-doped zinc sulfide NPs were considered under the correlation between Mn-doping level and their particle size. The highest photocurrent density (8.03 mA cm−2) and largest photoconversion efficiency (0.63%) (at 0.4 V vs. RHE) were reached at 6 mol% Mn. Based on the results of used various materials characterization techniques, including transmission electron microscopy (TEM), X-ray diffraction, photoluminescence spectrum, and absorbance spectrum, it can be assessed that the outstanding PEC characteristics of Mn:ZnS photoanode are attributed to the narrow bandgap of Mn:ZnS nanoparticles and their notably small particle size, which is originated from the Mn-doping. For application, the stability and the effect of various electrolytes were also investigated.

Surface modification of CuS counter electrodes by hydrohalic acid treatment for improving interfacial charge transfer in quantum-dot-sensitized solar cells

High charge transfer resistance and low electrocatalytic activity of counter electrodes (CEs) are mainly responsible for the poor photovoltaic performance of quantum-dot-sensitized solar cells (QDSSCs). Herein, a novel strategy has been successfully introduced for the first time to improve the electrocatalytic activity and charge transfer properties of a copper sulfide (CuS) CE by modifying it with the addition of hydrohalic acids (HHA). Through the suitable surface modification of HHA-incorporated CuS CE, the charge transfer from the external circuit to the CE surface was effectively facilitated. The electrochemical analyses suggest that charge transfer resistance is sufficiently reduced at the CE/electrolyte interface by using the HHA-treated CuS CEs. This improvement is mainly attributed to the high electrocatalytic activity of the modified CEs for the reduction of the polysulfide redox couple electrolyte in QDSSCs. The device constructed with TiO2/CdS/CdSe/ZnS photoanodes and the hydrogen-fluoride-treated CuS (HFCuS) CE exhibits a power conversion efficiency of 4.25%, which is considerably higher than that of the device with the bare CuS CE (3.11%). These findings can facilitate the fabrication of highly efficient CEs for next-generation solar cells.

Constructing high-performance H3PW12O40/CoS2 counter electrodes for quantum dot sensitized solar cells by reducing the surface work function of CoS2.

A low cost H3PW12O40 (PW12)/CoS2 complex is prepared and used as a counter electrode (CE) to combine with sandwich quantum dot sensitized solar cells (QDSSCs) composed of a TiO2/CdS/CdSe/ZnS photoanode and polysulfide electrolyte to study their photovoltaic properties via a simple hydrothermal method. Under standard simulated sunlight, the photoelectric conversion efficiency (PCE) of 2%PW12 (PW12-2/CoS2) doped CEs was 6.29%, which was significantly 67.7% higher than those of QDSSCs based on undoped CoS2 CEs (3.75%). Due to the introduction of PW12, the nanoparticles forming the hollow structure of CoS2 changed from regular octahedra to rough nanoparticles, which increase the active sites. At the same time, the work function of CoS2 decorated with PW12 is decreased. This study and discovery demonstrate that POMs can be used to optimize CE materials and improve the photoelectric conversion efficiency of QDSSCs, which provide an experimental and theoretical basis for subsequent investigations.

Control of the interfacial charge transfer resistance to improve the performance of quantum dot sensitized solar cells with highly electrocatalytic Cu-doped SnS counter electrodes

High charge transfer resistance at the interface between counter electrodes (CEs) and sulfide/polysulfide based electrolytes is responsible for the low photoelectrochemical performance of quantum dot sensitized solar cells (QDSSCs). Here, for the first time, we fabricated highly electrocatalytic and stable Cu-doped SnS CEs by inexpensive chemical bath deposition (CBD) method, to control the interfacial charge transfer resistance in QDSSCs and increase their photovoltaic performance. TiO2/CdS/CdSe/ZnS photoanodes and an aqueous polysulfide electrolyte were used to fabricate the QDSSCs with CEs. The QDSSCs with a 10% Cu-doped SnS CE achieved an outstanding conversion efficiency of 4.07% under standard simulated AM 1.5 illumination, exceeding that of a cell with an undoped SnS CE (2.80%). The surface morphologies of SnS CEs with different Cu contents were significantly different. The voids between SnS nanoparticles deposited on fluorine-doped tin oxide (FTO) substrate were reduced upon the uniform distribution of Cu dopants. The Cu-doped SnS CE had significantly improved electrocatalytic activity for catalysis during the reduction of electrolyte, low charge transfer resistance at the CE/electrolyte interface, and fast electron transport from SnS surface to the electrolyte to regenerate the redox couple. These findings may inspire the design of efficient CEs for the large-scale production of next-generation QDSSCs.

Quantum Dot Donor-Polymer Acceptor Architecture for a FRET-Enabled Solar Cell.

Forster resonance energy-transfer (FRET)-based solution-processed solar cell is fabricated with cadmium sulfide (CdS) as the energy donor and poly[ N-9'-heptadecanyl-2,7-carbazole- alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)] (PCDTBT) as the energy acceptor. Carbon dots (C-dots) deposited on carbon fabric are applied as a counter electrode. Although electron injection from CdS to PCDTBT is energetically disfavored, evidences for energy transfer between the two components of the cell are obtained in terms of FRET parameters with the relative quantum yield of donor CdS quantum dots (QDs) being ∼0.3, a Forster radius of ∼3.7 nm, and an energy-transfer efficiency of ∼55%. Power conversion efficiency (PCE) of the TiO2/PCDTBT cell without the donor is 0.23% and when coupled with donor CdS QDs, the ensuing TiO2/PCDTBT/CdS cell experiences a 23 time increment in PCE, reaching 5.3%. The complete FRET cell: TiO2/PCDTBT/CdS/ZnS-S2--C-dots/C-fabric produces a PCE of 7.42%, under 1 sun illumination. External quantum efficiency studies reveal an enhanced spectral response spanning from 300 to 670 nm, with 300 and 175% increases attained for the FRET-enabled TiO2/PCDTBT/CdS/ZnS photoanode compared with the TiO2/PCDTBT photoanode over the blue and green-red portions of the solar spectrum.

Z-scheme design of Ag@g-C3N4/ZnS photoanode device for efficient solar water oxidation: An organic-inorganic electronic interface

Abstract Herein, we demonstrate a design of a composite photoanode comprising a very thin layer of ZnS NPs onto a dense layer of Ag@g-C3N4 to form a dual absorber tandem device based on organic-inorganic electronic interface for photo water-splitting. The XRD pattern of Ag@g-C3N4 showed both the diffraction peaks of cubic Ag and main peak of g-C3N3. The XPS survey spectrum confirms the existence of the C, N, Ag, Zn, and S elements on the surface of the Ag@g-C3N4/ZnS photoelectrode. With incorporating Ag in g-C3N4 structure, the band gap decreased from 2.90 for g-C3N4 to 2.55 eV for Ag@g-C3N4 and also light absorption ability increased. The device based on the architecture of TiO2/Ag@g-C3N4/ZnS/Ni(OH)2 showed a photocurrent of about 0.1 and 0.2 mA cm−2 at potential of 1.23 and 1.7 V vs. RHE. The Ag@g-C3N4/ZnS photoanode exhibited a photocurrent turn-on potential of 0.45 V vs. RHE. In this photoanode device, Ag@g-C3N4 as a second absorber layer could absorb the photons of visible light which are transparent to ZnS layer and transforms into additional photovoltage. This architecture introduces a successful band alignment for high efficiency water-splitting through organic-inorganic junction.

Optical properties of composited TiO2-aluminium-doped ZnS photoanode

Abstract A composited photoanode for optoelectronic devices have widely attracted much attention for many decades. In this work, wide band gap semiconductors, ZnS, and aluminium-doped ZnS were synthesized through simply chemical synthetic route with band gap energy of 3.67 – 3.69 eV. The thin films of TiO2/ZnS and TiO2/aluminium-doped ZnS composites with various concentration were prepared by doctor blade technique. By means of X-ray diffraction, the thin film structures of TiO2 is rarely dominated by ZnS or aluminium-doped ZnS. A ruthenium sensitizer (N719) was sensitized on the composited thin films. The absorption and photoluminescence of the composited photoanode were characterized, indicating the band gap energy of 3.41 eV for all thin films. It was observed that both ZnS and aluminium-doped Zns reduce the amount of dye uptake. Also, the photoluminescence of dye sensitized TiO2/ZnS and TiO2/aluminium-doped ZnS photoanode was rather blue-shifted and enhanced with the increasing of ZnS or aluminium-doped ZnS amount. Moreover, using Time Correlated Single Photon Counting technique (TCSPC), the emission lifetimes of dye sensitized TiO2, TiO2/ZnS and TiO2/aluminium-doped ZnS anodes are 3.32 ns, 8.40 ns and 6.42 ns, respectively which indicate the charge injection from excited dye to photoanode.

Improvement photovoltaic performance of quantum dot-sensitized solar cells using deposition of metal-doped ZnS passivation layer on the TiO2 photoanode

The thin film of metal ions (Mn2+ and Cu2+) doped‑zinc sulfide (ZnS) as a passivation layer have been constructed on the TiO2 layer using the successive ionic layer adsorption and reaction (SILAR) method in quantum dot-sensitized solar cell (QDSSC). In the QDSSCs with Cu2S counter electrodes (CE), by doping photoanodes with Mn2+- and Cu2+-doped ZnS, about 40% and 22% improvements in efficiency have been observed compared to the cell based on the bare TiO2 film. Also, these photoanodes have been applied with CoS CE and their photovoltaic performance have been investigated. For both of the CEs, by incorporating Mn2+ ions in ZnS layer further increase have been observed in photocurrent compared to the cell based on the Cu2+-doped-ZnS. Electrochemical impedance spectroscopy (EIS) shows that ZnS layer decreases the recombination of electrons from the conduction band of TiO2 to the quantum dots or electrolyte, which is a beneficial effect on the photocurrent. The higher enhancement in photocurrent is attributed to the midgap states that the metal ions can create in the host material. The midgap states facilitate the charge transfer at the electrolyte/QD interface. By comparing the SEM images of the photoanods, it is found that the surface morphology of Mn2+ and Cu2+-doped ZnS photoanodes are differ from bare TiO2. The results suggest that the metal ions-doped-ZnS layer can be as an efficient passivation layer in the TiO2 photoanode. The above results prove that this optimization of the photoanode is as a simple method for enhancing photocurrent and power conversion efficiency in the QDSSCs.

Application of Chlorophyll as Sensitizer for ZnS Photoanode in a Dye-Sensitized Solar Cell (DSSC)

Zinc sulphide thin films have been synthesized by the electrodeposition method onto stainless steel substrate followed by dipping in acetone solution of chlorophyll in different time intervals to form photosensitised thin films. The photoelectrochemical parameters of the films have been studied using the photoelectrochemical cell having the cell configuration as follows \( {\rm{photoelectrode/NaOH}}\left({1\;{\rm{M}}} \right) + {\rm{S}}\left({1\;{\rm{M}}} \right) + {\rm{N}}{{\rm{a}}_2}{\rm{S}}\left({1\;{\rm{M}}} \right){\rm{/C}}\,\,\left({{\rm{graphite}}} \right)\). The photoelectrochemical characterization of the semiconductor film and dye-sensitised films has been carried out by measuring current–voltage (I–V) in the dark, power output and photoresponse. The study proves that the conductivity of both ZnS film and dye-sensitised ZnS films are n-type. The power output curves illustrate that open circuit voltage (Voc) and short circuit current (Isc) increase from 0.210 V to 0.312 V and from 0.297 mA to 0.533 mA, respectively. The fill factor initially decreases from 0.299 to 0.213 and then increases to 0.297 irregularly whereas efficiency increases from 0.047% to 0.123%. The UV–Vis absorbance spectrum of chlorophyll in acetone shows the presence of chlorophyll. The structural morphology of the ZnS thin films has also been analysed by using x-ray diffraction technique (XRD) and a scanning electron microscope (SEM). The XRD pattern shows the formation of nanocrystalline ZnS thin films of size 65 nm and the SEM images confirm the formation of fibrous film of ZnS. The energy diffraction analysis of x-ray confirms the formation of ZnS thin films.

Improving the efficiency of quantum-dot-sensitized solar cells by optimizing the growth time of the CuS counter electrode

CuS counter electrodes (CEs) were prepared to fabricate efficient quantum-dot-sensitized solar cells (QDSSCs) based on a CdS/CdSe photo sensitizer. The CEs were prepared on a fluorine-doped tin oxide (FTO) glass substrate by a facile chemical bath deposition (CBD) method by dissolving CuSO4·5H2O and CH3CSNH2 in water, followed by adding 0.25mM polyvinylpyrrolidone (PVP). The CBD was performed at 60°C for 1h, 2h, and 3h, and the samples were labeled as CuS 1h, CuS 2h, and CuS 3h, respectively. The QDSSCs were assembled using prepared CuS CEs and a TiO2/CdS/CdSe/ZnS photoanode, and the effect of the growth time of CuS CEs on the QDSSC performance was investigated. As the CuS growth time increases, the short-circuit current density (Jsc), fill factor (FF), and open-circuit voltage (Voc) of the QDSSCs gradually increases, leading to an enhanced power conversion efficiency (η). QDSSCs that use the CuS 2h CE exhibit a high Jsc of 14.31mAcm−2, Voc of 0.603V, and FF of 0.49, which are higher than that using conventional Pt electrodes as well as CuS 1h and CuS 3h electrodes. The electrochemical impedance spectroscopy results show that the CuS 2h CE exhibits an inferior charge transfer resistance of only 2.93Ω, which is 33 times lesser than that of the Pt CE. The enhanced device performance of CuS 2h is ascribed to the high catalytic activity and low charge transfer resistance of the CuS CE in the reduction process of oxidized polysulfide. Consequently, a superior power conversion efficiency of 4.27% is achieved for QDSSCs utilizing CuS 2h.

Influence of Surface Treatment and Annealing Temperature on the Recombination Processes of the Quantum Dots Solar Cells

We have studied the effect of the surface treatment of the CdS/CdSe quantum dots (QDs) by passivation ZnS layers and annealing temperature on the recombination resistance of the quantum dots solar cells (QDSSCs) based on TiO2/CdS/CdSe/ZnS photoanodes. The recombination resistance at TiO2/QDs contact and in TiO2film decreased when the QDs were added to the passivation ZnS layers. Furthermore, we used the F−ions linker and found the best annealing temperature conditions to reduce the recombination resistance of the QDSSCs. As a result, the current density increased from 7.85 mA/cm2to 14 mA/cm2.

Enhance the performance of quantum dot-sensitized solar cell by manganese-doped ZnS films as a passivation layer

To make quantum dot-sensitized solar cells (QDSSCs) more attractive, it is necessary to achieve higher power conversion efficiency. A novel Mn-doped ZnS has been successfully fabricated on CdS/CdSe quantum dots (QDs) by simple successive ion layer adsorption and reaction (SILAR) technique. The Mn-doped ZnS is used as a passivation layer in the QDSSCs. The performance of the QDSSCs was examined in detail using sulfide/polysulfide electrolyte with a Pt or copper sulfide (CuS) counter electrode. Here we demonstrated, the fabricated Mn-doped ZnS QDs shows an improved Voc (0.65V) compared to bare ZnS QDs (0.60V). The QDSSC based on a photoanode with Mn-doped ZnS (10wt% of Zn) shows higher Jsc (15.32mAcm−2) and power conversion efficiency (4.18%) compared to the bare ZnS photoanode (2.90%) under AM 1.5 G one sun illumination. We explore the reasons for this enhancement and demonstrated that it is caused by improved passivation of the ZnS surface by Mn ions, leading to a lower recombination of photo-injected electrons with the electrolyte. The effect of Cu ions in ZnS has been investigated by UV–Vis spectra and current density–voltage analysis.

A strategy to enhance the efficiency of dye-sensitized solar cells by the highly efficient TiO2/ZnS photoanode.

In dye-sensitized solar cells (DSSCs), the TiO2 photoanode film plays an important role in increasing the power conversion efficiency. In this work, TiO2 nanoparticles were first coated on fluorine-doped tin oxide by the doctor-blade method, and then a thin film of zinc sulfide (ZnS) was successfully fabricated on the surface of the TiO2 nanoparticles using the successive ionic layer adsorption and reaction method. The performance of the DSSCs was examined in detail using a cobalt sulfide counter electrode and I(-)/I3(-) electrolyte. X-ray diffraction and energy dispersive X-ray spectroscopy measurements were used to find the composition of the films. Characterization with electrochemical impedance spectroscopy indicated that the recombination rate decreased drastically during the electron transportation. The DSSCs based on ZnS coated TiO2 photoanode achieved a power conversion efficiency of 5.90% under 1 sunlight illumination, which is higher than that of the bare TiO2 photoanode (4.43%). This suggests that the promising ZnS-coated TiO2 nanoparticles accumulate a large number of photo-injected electrons in the conduction band of the photoanode and the N719 dye lowers the recombination of photo-injected electrons with the redox electrolyte.

The Dynamic Resistance of CdS/CdSe/ZnS Co-Sensitized TiO2 Solar Cells

Quantum dots' sensitized solar cells (QDSSCs) can create the high-performance and low-cost photovolta- ic in the future. In this study, we synthesized the film of TiO2/CdS/CdSe/ZnS photoanodes by successive ionic lay- er adsorption reaction (SILAR) method. The absorption spectra, photoluminescent spectra and electrochemical im- pedance spectra (EIS) of the film TiO2/CdS/CdSe/ZnS photoanodes show that the structure of energy levels in the conduction band (CB) of photoanode materials CdS, CdSe, and ZnS quantum dots (QDs) can absorb a great number of photons in each region and inject stimulated electrons quickly into the conduction band (CB) of TiO2. Furthermore, we also studied the influence of the SILAR cycles on the dynamic resistance, the lifetime of electrons in QDSSCs through Nyquist and Bode.

Photoactive p-type PbS as a counter electrode for quantum dot-sensitized solar cells

A photoactive PbS film synthesized by successive cycles of coating with ionic solutions and reaction can function as a performance-promoting counter electrode for quantum dot-sensitized solar cells (QDSSCs). The PbS film has a wide absorption spectrum that extends to the near infra-red region, making it capable of absorbing the long-wavelength light that penetrates the photoanode of a QDSSC. Under simulated one-sun illumination, this PbS film exhibits a p-type photovoltaic response in a polysulfide electrolyte, showing a quasi-Fermi level shift of +0.25 V. For QDSSCs consisting of a TiO2/CuInS2/CdS/ZnS photoanode and a polysulfide electrolyte, the PbS film outperforms Pt and CuS films as a counter electrode even though CuS has a much higher electrocatalytic activity in the polysulfide electrolyte than PbS. The photoactive characteristics of the PbS electrode increase the photocurrent of the resulting QDSSC. The p-type conductivity of the PbS forms a partial tandem junction between the PbS and the anode, increasing the photovoltage and the fill factor. Under one-sun illumination, a QDSSC assembled with the photoactive p-type PbS counter electrode achieves a maximum power conversion efficiency of 4.7%, which is more than 15% greater than that of a cell assembled with the highly electrocatalytically active CuS.

High-performance quantum dot-sensitized solar cells based on sensitization with CuInS2quantum dots/CdS heterostructure

A high-performance quantum dot-sensitized solar cell (QDSSC) is reported, which consists of a TiO2/CuInS2-QDs/CdS/ZnS photoanode, a polysulfide electrolyte, and a CuS counter electrode. The sensitization process involves attaching presynthesized CuInS2 QDs (3.5 nm) to a TiO2 substrate with a bifunctional linker, followed by coating CdS with successive ionic layer adsorption and reaction (SILAR) and ZnS as the last SILAR layer for passivation. This process constructs a sensitizing layer that comprises CdS nanocrystals, closely packed around the earlier-linked CuInS2 QDs, which serve as the pillars of the layer. The CuS counter electrode, prepared via successive ionic solution coating and reaction, has a small charge transfer resistance in the polysulfide electrolyte. The QDSSC exhibits a short-circuit photocurrent (Jsc) of 16.9 mA cm−2, an open-circuit photovoltage (Voc) of 0.56 V, a fill factor of 0.45, and a conversion efficiency of 4.2% under one-sun illumination. The heterojunction between the CuInS2 QDs and CdS extends both the optical absorption and incident photon conversion efficiency (IPCE) spectra of the cell to a longer wavelength of approximately 800 nm, and provides an IPCE of nearly 80% at 510 nm. The high TiO2 surface coverage of the sensitizers suppresses recombination of the photogenerated electrons. This results in a longer lifetime for the electrons, and therefore, the high Voc value. The notably high Jsc and Voc values demonstrate that this sensitization strategy, which exploits the quantum confinement reduction and other synergistic effects of the CuInS2-QDs/CdS/ZnS heterostructure, can potentially outperform those of other QDSSCs.

High performance and reduced charge recombination of CdSe/CdS quantum dot-sensitized solar cells

CdSe and CdSe/CdS quantum dots (QDs) with narrow size distribution are attached onto TiO2 electrodes by linker-assisted chemical bath deposition (LACBD). Preparation is carried out at 60 °C or 160 °C, which results in the formation of CdSe or CdSe/CdS QDs onto the TiO2 nanoparticles connected by thioglycolic acid (TGA). The solar cell based on a CdSe/CdS QD-sensitized TiO2 photoelectrode shows higher JSC, VOC and power conversion efficiency comparing to single CdSe QD-sensitized TiO2, which can be ascribed to superior light absorption, faster electron transport and slower charge recombination for the former. Furthermore, the effects of a ZnS passivation layer and thermal annealing on the photovoltaic performance have been investigated by UV-vis spectra, incident photo-to-current conversion efficiency (IPCE) and electrochemical impedance spectra (EIS). As a result, a quantum dot-sensitized solar cell (QDSSC) based on a TiO2–CdSe/CdS–ZnS photoanode (400 °C, 300 s calcination), polysulfide electrolyte and Cu2S counter electrode achieves a power conversion efficiency of 4.21% under AM 1.5 G one sun illumination.