Cu2S Counter Electrode Research Articles

Rational design and fabrication of skeletal Cu7S4 nanocages for efficient counter electrode in quantum dot-sensitized solar cells

The widely used brass based Cu2S counter electrodes (CEs) cannot stand the continuing corrosion in polysulfide electrolyte, which has limited the development of quantum dot-sensitized solar cells. Here, skeletal Cu7S4 nanocages (SKE-Cu7S4) with symmetric opening windows were rational designed and synthesized by kinetic roughening processes, and a possible formation mechanism had been proposed. Furthermore, SKE-Cu7S4 onto fluorine-doped tin oxide glass substrates were designed and deposited to function as new efficient, stable and low cost CEs. Thanks to the 3D opening structure of SKE-Cu7S4 CEs, the assembled QDSSCs exhibited a power conversion efficiency of 4.43% under 1 sun (100mWcm−2) irradiation, while those of preformed 18 facet-Cu7S4, Pt and brass/Cu2S CEs are of 3.87%, 1.73% and 3.32%, respectively. Further studies by cyclic voltammetry measurements indicate the SKE-Cu7S4 CEs still remain good cyclability after 600 cycles, demonstrating a super stable capability, while the commonly used brass/Cu2S CEs show obvious fluctuation.

CuInS2/Mn-CdS quantum dot co-sensitized flexible solar cells based on single fibrous TiO2 nanowire arrays

TiO2 nanowire arrays are prepared on Ti wire by a hydrothermal process, which are co-sensitized with CuInS2/Mn-CdS quantum dots to fabricate the solar cells with Cu2S/brass as the counter electrode. The UV–Vis absorption spectra observe that the deposition of CuInS2/Mn-CdS quantum dots on the TiO2 photoanodes obviously improves its optical absorption properties. The influence of the length of TiO2 nanowire arrays is also investigated, which indicates that the solar cells with 20 μm TiO2 nanowire arrays in length have the best photovoltaic performance. The diameter of Cu2S/brass counter electrode has a significant influence on the illuminated area and electrocatalytic ability of the solar cells. For comparison, the fibrous CuInS2/Mn-CdS quantum dot co-sensitized solar cells using the Cu2S counter electrode of 100 μm in diameter exhibits a photovoltaic power conversion efficiency of 3.51 %.

Copper selenide as a new counter electrode for zinc oxide nanorod based quantum dot solar cells

This work investigates the improvement in efficiency of quantum dot sensitized solar cells (QDSSCs) using copper selenide (Cu2Se) as a new counter electrode. Cu2Se counter-based QDSSC exhibits power conversion efficiency (η) of 2.28%, which is higher than the 1.17% efficiency of copper sulfide (CuS) counter electrode. Electrochemical impedance spectroscopy results show that by the changing counter electrode from CuS to Cu2Se, the charge transfer resistance at the counter electrode/electrolyte interfaces is reduced and, consequently, causes current density rise from 6.02mA/cm2 to 11.26mA/cm2. Also, open circuit voltage decay and dark current density–voltage results show that the lifetime of electron in the Cu2Se counter-based QDSSC is higher than that of QDSSC with CuS counter electrode. Therefore, Cu2Se counter electrode can be regarded as a promising alternative to the noble CuS counter electrode in QDSSCs.

Copper sulfide/Lead sulfide as a Highly Catalytic Counter Electrode for Zinc Oxide Nanorod Based Quantum Dot Solar Cells

This work investigates the improvement in efficiency of quantum dot sensitized solar cells (QDSSCs) using CuS/PbS as counter electrode, which results in formation of highly efficient counter electrode for liquid-junction QDSSCs. The QDSSC on based CuS/PbS counter electrode exhibits power conversion efficiency (η) of 2.2%, which is higher than that of CuS counter electrode, 1.17%. The improvement in η is probably attributed to the reduction of electron back into CuS/PbS counter electrode. Electrochemical impedance spectroscopy and cyclic voltammetry results confirm that higher value of η in CuS/PbS counter electrode is because of this novel counter electrode which shows superior photo-electrochemical performance and electro-catalytic properties. Another reason for this higher η might be the reduction in the charge transfer resistance at the counter electrode/electrolyte interfaces.

Influence of Cu vacancy on knit coir mat structured CuS as counter electrode for quantum dot sensitized solar cells.

Knit-coir-mat-like structured CuS thin films prepared by chemical bath deposition with different time duration were used as counter electrode in qunatum dot sensitized solar cells. The film deposited at 4 h exhibited better electrochemical and photovoltaic performance with JSC, VOC, and FF values of 14.584 mA cm(-2), 0.566 V, and 54.57% and efficiency of 4.53%. From the UV-vis absorption spectra, it is observed that CuS thin film exhibits free carrier intraband absorption in the longer wavelengh region. The enhanced performance of CuS counter electrodes is due to Cu vacancies with increased S composition, and the quasi-Fermi energy level in semiconductors with respect to electrolyte redox potential is one of the causes that affects the electrocatalytic activity of counter electrodes.

CdS/CdSe quantum dot-sensitized solar cells based on ZnO nanoparticle/nanorod composite electrodes

Zinc oxide (ZnO) films were deposited on fluorine-doped tin oxide (FTO) glass substrates with the application of polysulfide redox reactions and a CuS counter electrode to fabricate CdS/CdSe quantum dot-sensitized solar cells (QDSCs). In the present study, ZnO nanoparticles were deposited in the interstices of the ZnO nanorods. The performance of the QDSCs was improved by the ZnO nanoparticle/ nanorod composite structure because the ZnO nanorods exhibit high electron transport, and while the ZnO nanoparticles have a large surface area for QD deposition. The ZnO nanoparticle/nanorod composite films represent a promising achievement for enhancing the conversion efficiency of QDSCs. Open image in new window

Novel single pot synthesis of metal (Pb, Cu, Co) sulfide nanomaterials -Towards a quest for paintable electrode materials that supersedes Pt electrode

Novel single pot selective stoichiometric synthesis of cobalt, copper and lead sulfide nanomaterials has been carried out in an energy and time efficient manner by using combustion synthesis for the first time without using surfactants, capping agents and inert atmospheric conditions. X-ray diffraction and transmission electron microscope revealed the formation of respective nanocrystalline metal sulfides with different stoichiometry, whereas, electrochemical impedance analyses confirmed the low charge transfer resistance of all metal sulfide counter electrodes when compared to the Pt counter electrode, indicating their potential to be used as electrode materials. The efficiency of metal sulfide counter electrodes was tested in quantum dot sensitized solar cells (QDSSC) by applying the metal sulfide paint on fluorine doped tin oxide (FTO) plates. Current-voltage characteristics ratified the solar conversion efficiencies of 0.85, 1.3, 0.91 and 0.25, respectively for PbS (2), CuS (3), CoS (2) and Pt counter electrodes with CdS/TiO2 (1:1) working electrode and Na2S electrolyte. Thus the present study furnishes a novel method for the synthesis of metal sulfides as efficient paintable counter electrodes that can overcome Pt as counter electrode in QDSSC.

Fabrication of Cu1.8S/CuS nanoplates counter electrode via alternating current etching for quantum dots-sensitized solar cells

We demonstrate a method for fabricating a Cu1.8S/CuS nanoplate counter electrode (CE) via the alternating current (AC) etching of brass. The photoelectrochemical performance and electrocatalytic properties of Cu1.8S/CuS CE with a η value of 3.22% are much higher than those of Pt and conventional Cu2S CEs. Furthermore, it offers a simple and low cost method for producing CuS counter electrodes in the future.

Bifacial illuminated PbS quantum dot-sensitized solar cells with translucent CuS counter electrodes

This paper reports the optimization of the TiO2 photoanode and the fabrication of bifacial illuminated PbS quantum dot-sensitized solar cells (QDSSCs) with translucent CuS counter electrodes. TiO2 photoanode is prepared by introducing a compact TiO2 layer between FTO substrate and TiO2 film with titanium diisopropoxide bis(acetylacetonate) in 1-butanol and post-treatment with TiCl4 aqueous solution; then, PbS quantum dots (QDs) are deposited on the surface of TiO2 film by successive ionic layer adsorption and reaction method; also, by means of control of the TiO2 surface charge, QD density of TiO2 film is improved by adding triethanolamine into the cationic precursor solution. Using this optimized TiO2 photoanode and a translucent CuS counter electrode, a bifacial illuminated PbS QDSSC is fabricated. The preparation conditions are optimized and the surface morphology and electrochemical properties of TiO2 photoanodes are characterized. The bifacial illuminated PbS QDSSC achieves a power conversion efficiency of 2.16 %, which is increased by 48.97 % compared with the single illuminated QDSSC.

The effect of TiO2compact layer in ZnO nanorod based CdS/CdSe quantum-dot sensitized solar cell

CdS/CdSe quantum-dot sensitized solar cells (QDSCs) were fabricated from ZnO nanorods deposited on fluorine-doped tin oxide (FTO) substrates via the application of polysulfide redox reactions and a CuS counter electrode. In the present study, a TiO2 compact layer was used to suppress the recombination process. Typically, a TiO2 compact layer prevents direct contact between the FTO and electrolyte. The TiO2 compact layer with optimal thickness was fabricated by varying the soaking time in a TiCl4 solution. In addition, the morphology and influence of the compact layer on the interface between the FTO/electrolyte were analyzed.

Vertical nanosheet-structured ZnO/TiO2 photoelectrodes for highly efficient CdS quantum dot sensitized solar cells

Employing vertical nanosheet-structured films as photoanodes of quantum dot sensitized solar cells (QDSCs) might provide a direct pathway for the photo-exited electrons. Here, the vertical ZnO, ZnO/TiO2 and TiO2 nanosheet-structured films were prepared by a feasible deposition processes. These films were sensitized with CdS quantum dots and assembled with CuS counter electrodes to fabricate QDSCs. The photoelectric properties of ZnO/TiO2 composite films were superior to both pure ZnO and TiO2 films. The effects of TiO2 coating were investigated using electrochemical impedance spectroscopy (EIS). It was found that the photo-excited electron lifetimes in the photoanode were significantly improved with TiO2 layer. The optimum power conversion efficiency was about 1.95% under AM 1.5G illumination (100mW cm−2), with a short circuit current density, open circuit voltage, and fill factor of 6.11mAcm−2, 0.562V and 0.57, respectively.

A new in-situ preparation method to CuS electrodes for CdS/CdSe co-sensitized solar cells

A new in-situ preparation method to CuS electrodes has been developed by the combination of TICl4 treatment and chemical bath deposition (CBD). It is found that TiCl4 pre-treatment toward the substrates and post-treatment toward the CuS films are the key to high quality CuS films. Two kinds of CuS electrodes are obtained on Ti sheet and fluoride-doped SnO2 conductive glass (FTO), respectively. I-E polarization analysis and electrochemical impedance spectra reveal that this kind of CuS electrodes exhibits good interfacial electron transfer property and electrocatalytic activity. Up to 4.59% of light-to-electricity conversion efficiency has been achieved for CdS/CdSe -sensitized solar cells with our as-prepared CuS counter electrodes.

CdSe–CdS quantum dots co-sensitized ZnO hierarchical hybrids for solar cells with enhanced photo-electrical conversion efficiency

We have developed a facile method to fabricate CdSe-CdS quantum dot sensitized hierarchical ZnO nanostructures for quantum dot sensitized solar cells (QDSCs) by combining a hydrothermal method, successive ionic layer adsorption and chemical reaction (SILAR) techniques. The method consists of the growth of the ZnO hierarchical structure on ITO substrates via a hydrothermal method and the layer deposition of double quantum dots CdSe and CdS by SILAR. The CdSe-CdS QDs co-sensitized ZnO hierarchical structures show enhanced light absorption in the entire visible light range. The photovoltaic performance of QDCSs based on CdSe-CdS QDs co-sensitized ZnO hierarchical structures was evaluated. As photoanodes for QDSCs, the CdSe-CdS QDs double-sensitized ZnO hierarchical structures demonstrate an increased Jsc and improved power conversion efficiency of up to 1.39%. Under light illumination, photons are captured by QDs, yielding electron-hole pairs that are rapidly separated into electrons and holes at the interface between the ZnO and the QDs. The electrons are transferred to the conduction band of ZnO and the holes are released by redox couples in the liquid polysulfide (S(2-)/Sx(2-)) electrolyte, resulting in greatly improved photo-electrical conversion efficiency of QDSCs. The results suggest that it is very promising and feasible to enhance light absorption, carrier generation, and effective carrier separation via band engineering by CdSe-CdS QDs co-sensitization, and the method reported here displays a great potential for applications to be scaled up.

Enhanced Photovoltaic Performance in AgSbS2 Liquid-Junction Semiconductor-Sensitized Solar Cells

Ternary semiconductor AgSbS2 nanoparticles have been demonstrated to be a potential absorber material for solar cells. This work reports on the improved photovoltaic performance of liquid-junction AgSbS2 semiconductor-sensitized solar cells, prepared by growth of AgSbS2 nanoparticles on a nanoporous TiO2 electrode using the successive ionic layer adsorption and reaction process. The dependence of performance on the counter electrode and annealing atmosphere was investigated. The optimal performance was found in solar cells annealed in a N2 atmosphere with Au or Cu2S counter electrode. The best cell yielded a short-circuit current density Jsc of 8.30 mA/cm2, a open-circuit voltage Voc of 0.30 V, a fill factor of 32.8% and an efficiency η of 0.79% under 100 mW/cm2 light illumination. As the light intensity was reduced to 0.148 sun, the η increased to 1.28%, which is ∼ 300% larger than the η of 0.42% reported previously.

ITO@Cu2S Tunnel Junction Nanowire Arrays as Efficient Counter Electrode for Quantum-Dot-Sensitized Solar Cells

Quantum-dot-sensitized solar cell (QDSSC) has been considered as an alternative to new generation photovoltaics, but it still presents very low power conversion efficiency. Besides the continuous effort on improving photoanodes and electrolytes, the focused investigation on charge transfer at interfaces and the rational design for counter electrodes (CEs) are recently receiving much attention. Herein, core-shell nanowire arrays with tin-doped indium oxide (ITO) nanowire core and Cu2S nanocrystal shell (ITO@Cu2S) were dedicatedly designed and fabricated as new efficient CEs for QDSSCs in order to improve charge collection and transport and to avoid the intrinsic issue of copper dissolution in popular and most efficient Cu/Cu2S CEs. The high-quality tunnel junctions formed between n-type ITO nanowires and p-type Cu2S nanocrystals led to the considerable decrease in sheet resistance and charge transfer resistance and thus facilitated the electron transport during the operation of QDSSCs. The three-dimensional structure of nanowire arrays provided high surface area for more active catalytic sites and easy accessibility for an electrolyte. As a result, the power conversion efficiency of QDSSCs with the designed ITO@Cu2S CEs increased by 84.5 and 33.5% compared to that with planar Au and Cu2S CEs, respectively.

A Facile in Situ Synthesis Route for CuInS2 Quantum-Dots/In2S3 Co-Sensitized Photoanodes with High Photoelectric Performance

CuInS2 quantum-dot sensitized TiO2 photoanodes with In2S3 buffer layer were in situ prepared via chemical bath deposition of In2S3, where the Cd-free In2S3 layer then reacted with TiO2/CuxS which employed a facile SILAR process to deposit CuxS quantum dots on TiO2 film, followed by a covering process with ZnS layer. Polysulfide electrolyte and Cu2S on FTO glass counter electrode were used to provide higher photovoltaic performance of the constructed devices. The characteristics of the quantum dots sensitized solar cells were studied in more detail by optical measurements, photocurrent-voltage performance measurements, and impedance spectroscopy. On the basis of optimal CuxS SILAR cycles, the best photovoltaic performance with power conversion efficiency (η) of 1.62% (Jsc = 6.49 mA cm(-2), Voc = 0.50 V, FF = 0.50) under full one-sun illumination was achieved by using Cu2S counter electrode. Cu2S-FTO electrode exhibits superior electrocatalytic ability for the polysulfide redox reactions relative to that of Pt-FTO electrode.

An efficient and transparent copper sulfide nanosheet film counter electrode for bifacial quantum dot-sensitized solar cells

Copper sulfide (CuS) with nanosheet structure has been synthesized at a low temperature in situ on copper (Cu) film coated fluorine-doped tin oxide glass and bifacial quantum dot-sensitized solar cells (QDSSCs) were herein developed by using these CuS as counter electrodes (CEs). CuS is an environmental compatible and low toxic material. The obtained two-dimensional CuS nanosheet film presents high carrier mobility and exhibits highly catalytic performance for the polysulfide-based electrolyte. The QDSSC based on a CuS CE presents a power conversion efficiency (PCE) of 3.65% by optimizing the thickness of the Cu film under front illumination. The QDSSC based on a CuS CE prepared with a 200 nm thick Cu film shows a very close PCE under front and rear illuminations in which the values are as high as 2.70% and 2.40%, respectively. All the PCEs of the CuS CEs are much higher than that of the Pt CE (1.34%).

Highly efficient ZnO porous nanostructure for CdS/CdSe quantum dot sensitized solar cell

Porous zinc oxide (ZnO) nanostructure has been prepared by simple one step oxalate route for the fabrication of CdS/CdSe quantum dot sensitized solar cells (QDSSC). The porous ZnO photoanode is sensitized with CdS and CdS/CdSe quantum dots by simple chemical bath deposition technique by controlling the surface agglomeration of quantum dots over ZnO photoanode. The performances of the QDSSCs are examined with both platinum and copper sulfide counter electrodes. The photovoltaic properties of the cells are determined using current–voltage characterization under 1 sun illumination. The transport properties of the QDSSCs have been studied using electrochemical impedance spectroscopy and open circuit voltage decay analysis. The combination of CdS/CdSe/ZnS successive layers over ZnO with CuS counter electrode shows an excellent performance with a maximum power to conversion efficiency of 4.09% under 1 sun illumination.

Efficient CdS quantum dot sensitized solar cells made using novel Cu2S counter electrode

A novel Cu2S counter electrode (CE), which is prepared through simple electroplating method, is used to fabricate CdS quantum dot sensitized solar cells. The cells applying our novel CE show high power conversion efficiency in its class, reaching 2.6% under standard AM1.5 illumination, which is higher than those with Platinum CE (1.1%) and brass based Cu2S CE (1.85%). This is due to the novel CE showing superior photoelectrochemical performance and electrocatalytic property indicated by current density–voltage (J–V), the incident photon to current efficiency (IPCE) and the electrochemical impedance spectroscopy (EIS) curves.

Zn5(OH)8Cl2·H2O-based quantum dots-sensitized solar cells: A common corrosion product enhances the performance of photoelectrochemical cells

Exploiting new and efficient wide-band gap semiconductors is an important way to improve the performance of photoelectrochemical cells (dye-sensitized solar cells (DSSCs) and quantum dots-sensitized solar cells (QDSCs)). In this paper, Zn5(OH)8Cl2·H2O semiconductor that is a common corrosion product for zinc-contained materials in the electrolytes containing Cl− ions is for the first time explored as wide-band gap semiconductor in the photoelectrode of photoelectrochemical cells. The QDSCs based on CdS QDs-sensitized Zn5(OH)8Cl2·H2O nanosheets achieve the promising power conversion efficiencies of 0.62% and 1.11% for Pt and Cu2S counter electrodes, respectively. Furthermore, combining Zn5(OH)8Cl2·H2O and ZnO to form ZnO/Zn5(OH)8Cl2·H2O composite photoelectrode greatly increases the conversion efficiencies of QDSCs to 1.39% and 1.92% for Pt and Cu2S counter electrodes, respectively, which are higher than those based on conventional ZnO (1.11% and 1.53% for Pt and Cu2S counter electrodes, respectively) or TiO2 porous films (1.07% for Pt counter electrode). Therefore, Zn5(OH)8Cl2·H2O has shown much promise as an efficient wide-band gap semiconductor in the photoelectrode of photoelectrochemical cells.