PbS Counter Electrode Research Articles

Lead sulfide films synthesized by microwave-assisted chemical bath deposition method as efficient counter electrodes for CdS/CdSe sensitized ZnO nanorod solar cells

In this study, PbS thin films are deposited on FTO substrate via a rapid and facile microwave-assisted chemical bath deposition (MACBD) and then used directly as the counter electrodes (CEs) for CdS/CdSe quantum dots co-sensitized ZnO nanorods array solar cells (QDSSC). The resultant PbS CEs show good uniformity, strong adhesion to the FTO and superior electrocatalytic activity for the reduction of polysulfide electrolyte compared to the PbS CEs prepared with conventional CBD method. The combination of ZnO/CdS/CdSe photoanode with the optimum PbS CE shows appreciated power conversion efficiency (PCE) of 4.85%. The augmented photovoltaic performance can be attributed to its high electrocatalytic activity for polysulfide reduction in QDSSC, which results in a low charge transfer resistance at the interface of CE/electrolyte. The results demonstrate the potential application of this MACBD method in fabricating efficient metal sulfide counter electrode for QDSSC.

In Situ Growth of PbS Nanocubes as Highly Catalytic Counter Electrodes for Quantum Dot Sensitized Solar Cells

In this work, a face-centered cubic phase of galena PbS nanocubes, directly in situ grown onto conducting substrates, was fabricated by a facile chemical bath deposition method. The as-prepared PbS nanocubes show a highly crystalline structure and a quite uniform rectangular shape with approximate dimensions of 60–80 nm. These PbS nanocubes are demonstrated to act as excellent counter electrode (CE) materials in quantum dot sensitized solar cells (QDSCs) for electrocatalyzing polysulfide electrolyte regeneration. A CdS/CdSe QDSC constructed with a PbS nanocube-based CE yields a considerable power conversion efficiency of 3.49%. Moreover, the performance characterizations reveal that PbS CEs exhibit comparable electrocatalytic activity to the conventional Cu2S CEs while significantly outperforming the noble Pt CEs. Meanwhile, PbS CEs bypass the stability and contamination problems of Cu2S CEs. This work provides an alternative CE with advantages of high catalytic capability and stability as well as the ease of fabrication.

Interconnected nitrogen and sulfur co-doped graphene-like porous carbon nanosheets with high electrocatalytic activity as counter electrodes for dye-sensitized and quantum dot-sensitized solar cells

Interconnected nitrogen and sulfur co-doped graphene-like porous carbon nanosheets (NSGPCSs) are facilely produced by thermal annealing methyl orange (MO) doped polypyrrole (PPy) nanotubes at the presence of KOH under N2 atmosphere at 700 °C. The pyrolysis of PPy combined with the dedoping of PPy nanotubes derived from the interactions between KOH and MO lead to transforming 1D PPy nanotubes into 2D graphene-like carbon nanosheets. The as-prepared NSGPCSs have high specific surface area (up to 1744.98 m2 g−1) and hierarchical porosity, and are investigated as the counter electrodes for dye-sensitized and quantum dot-sensitized solar cells. The unique characteristics such as co-doping of nitrogen and sulfur heteroatoms, high specific surface area, and interconnected graphene-like nanosheets with hierarchical porosity render NSGPCSs a promising electrode material for photoelectrochemical cells. Electrochemical investigations indicate that NSGPCS electrodes display excellent electrocatalytic activity for the regeneration of the I−/I3− and polysulfide electrolytes. As a result, the dye-sensitized solar cell based on NSGPCS electrode achieves a conversion efficiency of 8.21%, which is very close to that of the cell based on conventional Pt electrode (8.61%). The efficiency of the quantum dot-sensitized solar cell assembled with NSGPCS counter electrode is significantly higher than that of the cell assembled with Pt counter electrode, and comparable to that of the cell assembled with PbS counter electrode.

A novel process for sensitization and infiltration of quantum dots in mesoporous metal oxide matrix for efficient solar photovoltaics response

Cadmium telluride (CdTe) quantum dots are integrated with mesoporous titanium dioxide “TiO2” electrode using an in-situ sensitization approach for the first time, where water soluble N-Acetyl Cysteine capped CdTe quantum dots (diameter 4–5 nm) are grown hydrothermally inside mesoporous TiO2 electrode matrix. This in-situ sensitization approach has shown the effective sensitization over the conventional reported sensitization processes. The in-situ CdTe sensitized TiO2 electrodes are further unified with PbS counter electrode to realize the quantum dot sensitized solar cell (QDSSC). The fabricated CdTe QDSSC has shown the optimal short circuit current density 3.35 ± 0.21 mA/cm2 and open circuit voltage 0.58 ± 0.01 V. The observed current density is the highest among such cell configurations, reported till date. The in-situ sensitized CdTe QDs are further treated with zinc sulfide for surface passivation to realize the reduced back recombination, if any. These ZnS passivated CdTe QDs sensitized solar cells in similar device configurations resulted into the significant reduction in the short circuit current density (20%) with the minimal change in open circuit voltage (5%). The impedance spectroscopy measurements suggest that the transmission resistance “Rtr” has increased after ZnS treatment for these electrodes, however, the recombination resistance Rrec has not changed much. The observed high Rtr might be responsible for the observed current deterioration after ZnS surface passivation. These studies suggest that in-situ QD sensitization may provide a new method of integrating QDs into mesoporous TiO2 matrix for effective QDSSC device performance without any additional surface passivation.

Octahedron shaped lead sulfide nanocrystals as counter electrodes for quantum dot sensitized solar cells

PbS nanocrystals with octahedron shape are synthesized by a low temperature approach with presence of cation/anion surfactants in aqueous solution. CdS quantum dot sensitized solar cells (QDSSCs) based on these novel octahedron shaped PbS counter electrodes (CEs) are fabricated for the first time, achieving PCE of 1.54%. It is observed that the octahedron shaped PbS CE shows higher electrocatalytic activity compared with the Pt CE, indicating that the PbS nanocrystals with a uniformly distributed size is a superior candidate as CEs for QDSSCs application. This work may provide new route for preparing PbS from aqueous solvent medium through a simple synthesis route.

Graphene/CuS/PbS nanocomposite as an effective counter electrode for quantum dot sensitized solar cells

In this paper, we introduce graphene/CuS/PbS nanocomposite as an effective counter electrode (CE) for quantum dot sensitized solar cells (QDSCs). The result indicated that the catalytic performance of CuS/PbS CEs was enhanced by pre deposition of graphene (G) sheets on the fluorine doped tin oxide (FTO) coated glass substrates. Here, various CEs are made by the simple successive ionic layer adsorption and reaction (SILAR) method. The result indicates that the fill factor of the cells with FTO/G/CuS/PbS CEs enhances in compare with the FTO/CuS/PbS CEs. Here, for the CdS/CdSe QD sensitized cells and G/CuS/PbS CEs, the cells' efficiency and fill factor is obtained 3.21% and 0.51 respectively which is enhanced compared to the CuS/PbS CEs with 2.54% efficiency and 0.36 fill factor. The present results indicate that the compact structure of the CuS/PbS CEs, replaces with a porous structure after graphene pre deposition which is expected to enhance the electrolyte/CE interface and consequently the fill factor. According to the obtained results, in spite of the poor catalytic activity of the graphene in the polysulfide electrolyte, it simply modifies the morphology of the CuS/PbS CEs for enhancing their performance. The results also demonstrated that G pre deposition can be systematically applied to enhance the performance of CEs in QDSCs.

The synthesis and characterization of lead sulfide with cube-like structure as a counter electrode in the presence of urea using a hydrothermal method

PbS counter electrodes at different concentrations of urea.

High catalytic activity of a PbS counter electrode prepared via chemical bath deposition for quantum dots-sensitized solar cells

A PbS counter electrode (CE) has been fabricated by a chemical bath deposition method, and can function as a counter electrode with high catalytic activity for quantum dots-sensitized solar cells (QDSSCs).

Enhanced photovoltaic performance and morphological control of the PbS counter electrode grown on functionalized self-assembled nanocrystals for quantum-dot sensitized solar cells via cost-effective chemical bath deposition

This study describes the synthesis of monodispersed PbS nanocrystals by a facile chemical bath deposition and cost-effective approach.

One-step synthesis of solution processed time-dependent highly efficient and stable PbS counter electrodes for quantum dot-sensitized solar cells

A QDSSC with time-dependent optimized PbS CE exhibits a higherηof 4.61% than that of Pt CE (1.34%).

Flexible quantum dot-sensitized solar cells with improved efficiencies based on woven titanium wires

Uniform zinc oxide (ZnO) nanosheet arrays were grown on woven titanium wires using a low temperature hydrothermal method. Photoanodes were prepared by depositing CdS and CdSe quantum dots onto the ZnO nanosheet arrays by a successive ionic layer adsorption and reaction (SILAR) method. Solar cells were assembled using these nanostructured photoanodes and their photovoltaic performance was characterized. The effect of using SILAR cycles for the deposition of quantum dots on the performance of these nanostructured solar cells was investigated systematically. The overall light-to-electricity conversion efficiency of 0.98% was achieved under 100 mW cm−2 illumination for flexible CdS/CdSe co-sensitized solar cells using conventional Pt foils as counter electrodes. To further improve the performance of the flexible solar cells, PbS and Cu2S counter electrodes based on Pb and Cu foils were fabricated. The best conversion efficiencies of flexible CdS/CdSe co-sensitized solar cells using Cu2S and PbS counter electrodes were 3.4% and 2.5%, which demonstrated a significant enhancement in values for short circuit current, open circuit voltage, and fill factor compared to those obtained with the commonly used Pt and Au electrodes.

ZnO/PbS core/shell nanorod arrays as efficient counter electrode for quantum dot-sensitized solar cells

To improve the electrochemical catalytic activity of the counter electrode (CE) to polysulfide electrolyte that commonly applied in quantum dot-sensitized solar cells (QDSSC), combination of catalysts with nanostructured materials is equally important as it is in the case of photoanodes. Here, we design and fabricate a new catalytic electrodes by combining PbS nanoparticles catalyst with ZnO nanorods arrays (NRs) for use as CEs in QDSSC. The ZnO/PbS core/shell CEs are prepared via the combination of chemical bath deposition and successive ionic layer adsorption and reaction methods. Compared with planar CEs, the ZnO NRs framework presents larger surface area for loading more PbS catalysts and easy accessibility of electrolyte. Additionally, the ZnO NRs core offers an excellent electron pathway for shuttling electrons to highly catalytic PbS sites due to the high electrical conductivity of ZnO nanorods. Therefore, the ZnO/PbS composite CEs exhibit much higher catalytic activity for polysulfide electrolyte than conventional Pt CE. As a result, the power conversion efficiency of QDSSC with the optimized ZnO/PbS CEs increase by nearly 120% and 78% compared to that with planar Pt and bare PbS CE, respectively.

Preparation of a Highly Efficient PbS Electrode and Its Application in Quantum Dots-Sensitized Solar Cells

To improve the light-to-electric conversion efficiency of quantum dots-sensitized nanocrystalline thin-film solar cells, a PbS electrode with high electrocatalytic activity toward polysulfide electrolyte was prepared by successively treating Pb foil in acid and polysulfide solutions. Electrochemical impedance spectroscopy(EIS)measurements were performed to evaluate the electrocatalytic activity of the prepared PbS electrode. Based on the EIS results, the temperature and time to treat the Pb foil in the acid solution were optimized. The PbS electrode prepared under the optimized conditions was used as a counter electrode to fabricate a quantum dotssensitized solar cell with a CdSe quantum dots-sensitized TiO2 nanocrystalline thin film as the photoanode and polysulfide solution as the electrolyte. Both the electrocatalytic activity and light-to-electric conversion properties of the PbS electrode prepared from acid treatment of Pb foil for the optimized temperature and time are superior to those of electrodes prepared by other reported methods. In our method, the treatment time is considerablyless but the PbS counter electrode maintains a superior catalytic activity compared with other methods. X-ray diffraction and scanning electron microscopy were performed to demonstrate the formation process of PbS,and the catalytic enhancement mechanism of the prepared PbS electrode is discussed.

Improved performance of CdS/CdSe quantum dot-sensitized solar cells using Mn-doped PbS quantum dots as a catalyst in the counter electrode

This study reports the enhanced catalytic ability of Mn-doped PbS QDs synthesized using a successive ionic layer adsorption and reaction (SILAR) method for quantum dot-sensitized solar cells (QDSSCs). Electrochemical and optical analysis of each material showed that the catalytic ability of the PbS electrode was improved significantly by Mn2+ doping. Two factors can explain this behavior. The first is that intentional impurities have an impact on the structure of the host material, such as increases in surface roughness. The other is that dopants create new energy states that delay the exciton recombination time and allow charge separation to be activated. As a result, the photoelectron supply from the counter electrode is accelerated, resulting in vigorous redox reactions at the polysulfide electrolyte. The performance of the CdS/CdSe QDSSC using a Mn-doped PbS counter electrode was compared with those using the Pt and PbS counter electrodes. Finally, a power conversion efficiency of 3.61% was achieved with the Mn-doped PbS counter electrode (VOC=0.61V, JSC=11.67mAcm−2, FF=0.51) under one sun illumination (100mWcm−2), which is ∼40% higher than that of CdS/CdSe QDSSCs with the bare PbS counter electrode.

Influence of highly efficient PbS counter electrode on photovoltaic performance of CdSe quantum dots-sensitized solar cells

PbS electrode with high catalytic activity to Sn 2− reduction certificated by the measurements of electrochemical impedance spectroscopy and cyclic voltammetry was prepared by a simple method. The high catalytic activity makes it be a low-cost alternative counter electrode to platinum (Pt) to be used in quantum dots-sensitized solar cells (QDSSCs) based on polysulfide electrolyte. The photovoltaic performance enhancement of the quantum dots (QDs)-sensitized semiconductor thin films due to the PbS counter electrode was evaluated by fabricating QDSSCs based on CdSe QDs-sensitized ZnO (SnO2) thin film. CdSe QDs-sensitized ZnO thin film has the lower internal total series resistance and electron transmission time, the higher electron lifetime and electron collection efficiency than the CdSe QDs-sensitized SnO2 thin film. Replacing the Pt counter electrode with the PbS counter electrode leads to more improvement on the short circuit photocurrent density for QDSSC based on the ZnO thin film than the SnO2 thin film. Therefore, the process to limit the photovoltaic performance of CdSe QDs-sensitized solar cell and the possible way to improve the photovoltaic performance were analyzed.

ITO Porous Film-Supported Metal Sulfide Counter Electrodes for High-Performance Quantum-Dot-Sensitized Solar Cells

In this paper, ITO porous films were prepared by the doctor-blade technique to support metal sulfide (CuS, CoS, NiS, and PbS) counter electrodes (CEs) in quantum-dot-sensitized solar cells (QDSCs). The successive ionic layer adsorption and reaction (SILAR) method was used to deposit metal sulfides on the ITO porous films. Since the ITO porous films have high mechanical properties and could offer a large surface area for the large deposition of metal sulfides, the ITO porous film-supported metal sulfide CEs exhibited much higher catalytic activity for polysulfide electrolyte than ITO glass-supported metal sulfide CEs. As a result, the photoeletrochemical performance of QDSCs was greatly improved. In addition, ITO porous film-supported CuS CEs at 12 SILAR cycles exhibited the highest catalytic activity and performance among different CEs, and ITO porous film-supported CoS CEs achieved the second highest catalytic activity and performance, still far higher than the Pt CE, while both ITO porous film-supported NiS and PbS CEs showed similar catalytic activity and performance, significantly lower than that of Pt CE. It is also suggested that many more CE materials can be easily explored and investigated by employing ITO porous films as substrates.

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.

PbS as a Highly Catalytic Counter Electrode for Polysulfide-Based Quantum Dot Solar Cells

We show that a significant improvement of the light to electric power conversion efficiency of quantum dot sensitized solar cells with a polysulfide electrolyte can be achieved when a PbS counter electrode is used. An acid pretreatment of a Pb metal foil followed by dipping into polysulfide solution provides a counter electrode which improves the short circuit current, open circuit voltage, and fill factor compared to commonly used Pt electrodes. Electrochemical impedance spectroscopy reveals a low charge transfer resistance between polysulfide and PbS, indicating the high catalytic activity of PbS. Moreover, a comparison with reported charge transfer resistance values at open circuit potential for alternative counter electrodes for polysulfide shows that PbS is the most catalytic of all. For a CdSe quantum dot sensitized mesoporous TiO2 electrode, we achieved a conversion efficiency of 3% using PbS as a counter electrode.