Counter Electrode For Dye-sensitized Solar Cells Research Articles

Fully Additively Manufactured Counter Electrodes for Dye-Sensitized Solar Cells.

In dye-sensitized solar cells (DSSCs), the counter electrode (CE) plays a crucial role as an electron transfer agent and regenerator of the redox couple. Unlike conventional CEs that are generally made of glass-based substrates (e.g., FTO/glass), polymer substrates appear to be emerging candidates, owing to their intrinsic properties of lightweight, high durability, and low cost. Despite great promise, current manufacturing methods of CEs on polymeric substrates suffer from serious limitations, including low conductivity, scalability, process complexity, and the need for dedicated vacuum equipment. In the present study, we employ and evaluate a fully additive manufacturing route that can enable the fabrication of CEs for DSSCs in a high-throughput and eco-friendly manner with improved performance. The proposed approach sequentially comprises: (1) material extrusion 3-D printing of polymer substrate; (2) conductive surface metallization through cold spray particle deposition; and (3) over-coating of a thin-layer catalyzer with a graphite pencil. The fabricated electrodes are characterized in terms of microstructure, electrical conductivity, and photo-conversion efficiency. Owing to its promising electrical conductivity (8.5 × 104 S·m-1) and micro-rough surface structure (Ra ≈ 6.32 µm), the DSSCs with the additively manufactured CEs led to ≈2.5-times-higher photo-conversion efficiency than that of traditional CEs made of FTO/glass. The results of the study suggest that the proposed additive manufacturing approach can advance the field of DSSCs by addressing the limitations of conventional CE manufacturing platforms.

Enhancement in the Electrocatalytic and Optoelectronic Performance of Cost-Effective Counter Electrode VO2 for Dye-Sensitized Solar Cell (DSSC)

Dye-sensitized solar cells (DSSCs) have garnered significant attention in the scientific community for more than two decades due to their cost-effectiveness, convenient manufacturability, little toxicity, and straightforward preparation methodology. In this study, we present a cost-effective alternative to the platinum electrode for DSSCs, which serves as the counter electrode. The utilization of vanadium oxide nanoparticles as counter electrodes (CEs) in DSSCs has been the subject of research due to its enhanced stability, cost-effectiveness, and favorable photovoltaic characteristics. The device has been fabricated in configuration of fluorine-doped tin oxide (FTO)||TiO2||ruthenium (II) dye (N719)||iodide—triiodide electrolyte||VO2 (counter electrode)||FTO and investigate their photovoltaic performance. The utilization of X-ray diffraction (XRD) analysis has provided insights into the crystalline properties of VO2, indicating that it exists in a crystalline phase with a crystalline size measuring 43.19 nm and a lattice strain of 1.68 × 10−3. The utilization of a field emission scanning electron microscope (FESEM) that is equipped with an energy dispersive X-ray spectrum reveals a dense microstructure characterized by a uniform distribution of vanadium (V) and oxygen (O) across the whole surface. The Raman spectroscopic examination of VO2 reveals the existence of many Raman bands, thereby confirming the presence of the monoclinic phase. Cyclic voltammetry measurements were employed to investigate the catalytic activity of the CE toward the electrolyte. The photovoltaic performance of the manufactured device was examined by I–V measurement, revealing a notable open circuit voltage (Voc) and efficient power conversion efficiency when compared to the other materials that were evaluated.

Bismuth sulfide/carbon black: as a pt free and efficient counter electrode in DSSC

A hydrothermal method was utilized to synthesize microstructures of bismuth sulfide (Bi2S3) across a range of reaction temperatures, spanning from 140 to 180 °C. The impact of varying reaction temperatures on the structural, morphological, and optical properties of the deposited Bi2S3 material was thoroughly examined. The x-ray diffraction (XRD) patterns confirmed the presence of an orthorhombic crystal structure. The formation of intricate three-dimensional Bi2S3 microstructures was evident under field emission scanning electron microscopy (FESEM), with the reaction temperature playing a pivotal role in this process. Furthermore, Bi2S3-carbon black composites were employed as the counter electrode in dye-sensitized solar cell (DSSC) applications. The current density–voltage characteristics of the DSSCs revealed a clear correlation between photoconversion efficiency and the reaction temperature. Notably, the Bi2S3-carbon black film with a 1:1 ratio achieved a peak photoelectric conversion efficiency of 4.37 ± 0.01%. It also exhibited a short-circuit current density of 10.29 mA cm−2 and an open-circuit potential of 0.70 V. Future studies should explore the broader implications of Bi2S3-carbon black composites in various optoelectronic and photocatalytic devices. Secondly, while our findings provide valuable insights, a more in-depth understanding of the underlying mechanisms governing the enhanced photoconversion efficiency, especially with the 1:1 ratio of Bi2S3-carbon black, requires further exploration.

Ni and P co-doped WS2 nanosheets decorated on MWCNTs as an efficient counter electrode for dye-sensitized solar cells

Designing of inexpensive and robust counter electrode (CE) material without noble metals is of great essential for improving the overall power conversion efficiency (PCE) of dye-sensitized solar cells (DSSCs). Herein, nickel (Ni) and phosphorus (P) co-doped WS2 nanosheets decorated on multi-walled carbon nanotubes (Ni/P-WS2 @MWCNTs) was fabricated via single-step hydrothermal method and used as CE for DSSC. According to the electrochemical studies, the Ni/P-WS2 @MWCNTs CE displayed remarkable catalytic activities, great electron transfer ability, and high durability in the I−/I3− electrolyte. More importantly, the device equipped with Ni/P-WS2 @MWCNTs CE yielded an outstanding PCE of 8.62%, surpassing that of standard Pt (PCE=6.61%) and other corresponding counterparts. Such notable photovoltaic performance can be ascribed to the synergistic coupling effect of heteroatom doping and support role of conductive carbon network, which offer abundant catalytic active sites, high porosity, and exceptional electrical conductivity. Our work suggests a novel strategy to fabricate Pt-like CE materials based on metal and nonmetal heteroatoms co-doped in metal chalcogenides with excellent performances for large-scale energy conversion devices to reach the consumer market.

The brief study of ZnO/PEDOT:PSS counter electrode in DSSC Based on solid electrolyte YSZ

Dye-Sensitized Solar Cell (DSSC) is a photovoltaic technology that is eco-friendly, has affordable costs, an easy fabrication process, and high power conversion efficiency. The application of solid electrolytes in DSSC is a promising option compared to using liquid electrolytes because liquid electrolytes easily cause corrosion on the photoanode and counter electrode. The role of the counter electrode in DSSC is crucial to speed up the electron transfer process to enhance the performance of DSSC devices. Much research on DSSC still uses a lot of platinum and graphene which are relatively expensive and supplies are limited. Therefore, this research will develop a low-cost and easy to fabricate counter electrode made of ZnO/PEDOT:PSS composite. Adding ZnO in PEDOT:PSS polymer can obtain higher catalytic activity, that can accelerate oxidation–reduction reactions to improve the performance of DSSC solar cells. From the results of this study, it can be concluded that the addition of ZnO mass to the ZnO/PEDOT: PSS composite can increase lattice parameters, crystal size, porosity values, and light absorbance. Based on the I-V testing, it shows that the addition of ZnO mass to the ZnO/PEDOT:PSS composite results in the highest efficiency of 3.29%.

Application of rice husk as a carbon source for substitution of sensitizer and counter electrode material in dye-sensitized solar cells

The third generation of solar cells is dye-sensitized solar cells (DSSC). DSSC can convert solar energy into electrical energy. The main components of DSSC include working electrode, counter electrode, sensitizer, and electrolyte. Substitution of commercial chemicals for the sensitizer (N719) and the counter electrode (platinum) of DSSC will lower the cost of DSSC fabrication. This study focuses on Nitrogen-Doped Carbon Quantum Dots (N-CQDs) synthesized from rice husks as a sensitizer. Then, DSSC with sensitizer of N719 (Pt-1) and N-CQDs (Pt-2) were compared. Furthermore, the N-CQDs residue in solid carbon was used as the counter electrode material using different sensitizers N719 (C-1) and N-CQDs (C-2). Based on the results, the FTIR characterization of N-CQDs showed the functional groups N-H, O-H, C=O, and CN. The UV-VIS characterization of N-CQDs had absorbance in the wavelength range of 200-400 nm. Pt-2 has an efficiency value of 0.258%, Jsc of 2.188 mA/cm2 Voc of 0.6 volts, and FF of 0.20. C-2 has an efficiency of 0.0010%, Jsc of 0.042 mA/cm2 Voc of 0.131 volts, and FF of 0.17. This confirms that N-CQDs can be used as a sensitizer and counter electrode material, although the results are not as good as commercial chemicals.

Screen-printed counter-electrodes based on biochar derived from wood-corn silage and titanium isopropoxide binder as a more efficient and renewable alternative to Pt-CE for dye-sensitized solar cells

Current research of counter-electrodes (CEs) for dye-sensitized solar cells (DSSCs) focuses mainly on searching for low-cost and mass-production suitable materials as an alternative to standardly used platinum. One of the most studied groups is carbon allotropes, while carbon-enriched materials such as biochar prepared from renewable sources (biomass) show tremendous potential. Structural properties of biochar, electrical conductivity and large specific area predict the possibility of its use as a catalytic material of CE. To ensure printability and efficient contact between the printed catalytic layer and substrate of CE, non-conductive polymer binders, reducing electrical and electrochemical properties of CEs, are standardly used. This work introduces the preparation of screen-printed CEs based on titanium isopropoxide (TTIP) binder and biochar microparticles obtained by pyrolysis of wood and corn silage, which were investigated as an alternative to platinum CE. TTIP was examined as a substitute for the polymer binder ethylcellulose (EC) and as the precursor for TiO2 nanoparticle synthesis in biochar/TTIP hybrid CEs. Formation of polymer matrix from TTIP ensured the required rheological properties of biochar/TTIP inks and improved interparticle contact and mechanical stability of screen-printed catalytic layers of CEs. Raman spectroscopy indicated the presence of TiO2 anatase nanoparticles with a size of 5 nm after CEs sintering at 500 °C under an argon atmosphere. The sintering process raised catalytic activity and decreased sheet resistance of CEs in the presence of I3−/I− electrolyte, resulting in enhanced photovoltaic parameters of DSSCs. Screen-printed composite CEs consisting of 30 wt% biochar and 20 wt% TTIP reached the best catalytic activity and higher conversion efficiency of DSSCs (6.43 %) than DSSCs with Pt CEs (6.19 %). Based on the results, combining biochar and TTIP offers new possibilities for developing more ecological and low-cost mass-producible materials for CEs.

Characterization of carbon derived from candle by flame-soot method for counter electrodes of dye-sensitized solar cells

Candle soot, carbon samples prepared by flame-soot method, was characterized and investigated for its catalytic ability for the reduction of tri-iodide ions aiming to substitute expensive platinum based electrode used in dye-sensitized solar cells (DSCs). The Energy Dispersive X-ray Spectroscopy of the candle soot samples revealed that the soot contains 96% carbon. Similarly, Scanning Electron Microscopy images show that the candle soot consists of interconnected carbon nanoparticles of size ∼50 nm. Furthermore, X-ray Diffraction and Raman spectroscopy showed that the candle soot consists of disordered and ordered graphitic carbons in a comparable proportion. The catalytic ability of the candle soot was compared with that of platinum by Electrochemical Impedance Spectroscopy of the symmetrical electrochemical cells. The charge transfer resistance (Rct) at the candle soot-electrolyte interface was observed to be ∼4.42 Ω cm2 compared to ∼ 5.04 Ω cm2 that of the platinum-electrolyte interface. The candle soot was prepared by a simple method using low-cost material; hence, it can be a low-cost and efficient counter electrode material alternate to the platinum used in counter electrodes of DSCs.

Highly efficient nitrogen-doped reduced graphene oxide-Sr0.7Sm0.3Fe0.4Co0.6O2.65 nanocomposites utilized as a counter electrode in dye-sensitized solar cells

Dye-sensitized solar cells (DSSCs) are known for their aesthetic properties, not limited to colour tuneability and transparency, but are also promising renewable energy technology that can efficiently harvest sunlight to generate electricity without releasing toxic gases. DSSCs are one of the potential candidates for fabricating colourful and see-through solar cells for energy-harvesting aesthetic windows. However, a trade-off between transparency and power conversion efficiency (PCE) has to be tackled amicably to realize solar cells with good PCE and transparency. Judicious selection of dyes to bypass light absorption in the high eye-sensitivity region (500 – 600 nm) is one of the plausible solutions. Most importantly, developing novel counter electrode materials using facile preparation techniques, low-cost materials, and environmentally friendly conditions helps overcome the limitations of commonly used but expensive and corroding metals, thereby improving the PCE of DSSCs. Herein, we report the synthesis of a novel hybrid nitrogen-doped reduced graphene oxide-Sr0.7Sm0.3Fe0.4Co0.6O2.65 (N-RGO-SSFC) nanocomposite using the thermal treatment method. The N-RGO-SSFC nanocomposites were characterized using microscopic and spectroscopic techniques and applied as counter electrodes in DSSCs. Scanning electron microscopy images revealed the presence of N-RGO sheets decorated by SSFC nanoparticles. The introduction of SSFC nanoparticles onto N-RGO sheets led to the formation of nanocomposites with a tetragonal structure, a surface area of 178.0 m2 g-1, an electrical conductivity of 13.02 S cm-1, and a charge transfer resistance of 10.6 Ω. The N-RGO-SSFC nanocomposite counter electrodes resulted in DSSCs with an enhanced PCE of 6.64% due to the formation of excellent electron transfer pathways. This outperformed DSSCs based on the Pt reference electrode with a PCE of 5.52%. Hence, N-RGO-SSFC nanocomposites can be applied as a potential counter-electrode material in DSSCs.

Dye-sensitized solar cells based on critical raw material-free Fe–N–C counter electrodes

Dye-sensitized solar cells (DSSCs) rely heavily on the counter electrode for their performance, which is responsible for collecting and transferring electrons generated at the photoanode. While platinum (Pt) has traditionally been used as a counter-electrode material, its cost, limited availability, and environmental concerns make it an unsuitable option for large-scale implementation. Iron–nitrogen––carbon (Fe–N–C) catalysts are receiving increasing attention due to their high catalytic activity and low cost. This study aims to investigate the performance of Fe–N–C materials as counter electrodes in DSSCs and assess their potential as a sustainable alternative to currently used platinum. Two different Fe–N–C-based materials have been synthesized using different carbon and nitrogen sources, and their electrochemical behavior has been assessed using current–voltage curves and impedance spectroscopy. The catalyst comprised a higher amount of iron and nitrogen shows higher efficiency and lower charge-transfer resistance due to improved iodide reaction kinetics and proper stability under potential cycling. However, this catalyst shows lower stability under a passive ageing procedure, which requires further clarification. Results provide new insights into the performance of Fe–N–C-based materials in DSSCs and aid in the further development of this promising technology.

Efficient One-Step Synthesis of a Pt-Free Zn0.76Co0.24S Counter Electrode for Dye-Sensitized Solar Cells and Its Versatile Application in Photoelectrochromic Devices.

In this study, we synthesized a ternary transition metal sulfide, Zn0.76Co0.24S (ZCS-CE), using a one-step solvothermal method and explored its potential as a Pt-free counter electrode for dye-sensitized solar cells (DSSCs). Comprehensive investigations were conducted to characterize the structural, morphological, compositional, and electronic properties of the ZCS-CE electrode. These analyses utilized a range of techniques, including X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The electrocatalytic performance of ZCS-CE for the reduction of I3- species in a symmetrical cell configuration was evaluated through electrochemical impedance spectroscopy and cyclic voltammetry. Our findings reveal that ZCS-CE displayed superior electrocatalytic activity and stability when compared to platinum in I-/I3- electrolyte systems. Furthermore, ZCS-CE-based DSSCs achieved power conversion efficiencies on par with their Pt-based counterparts. Additionally, we expanded the applicability of this material by successfully powering an electrochromic cell with ZCS-CE-based DSSCs. This work underscores the versatility of ZCS-CE and establishes it as an economically viable and environmentally friendly alternative to Pt-based counter electrodes in DSSCs and other applications requiring outstanding electrocatalytic performance.

Synergistic effect of interface and defect engineering of MoC/MoO2 nano dot encapsulated N-doped carbon nanoflowers for highly durable dye-sensitized solar cells

The design and fabrication of advanced counter electrodes (CEs) for dye-sensitized solar cells (DSSCs) are limited by the scarcity of active sites and poor durability. Herein, we report the controlled preparation of a heterostructured nanoreactor CE based on defect-rich N-doped carbon nanoflowers (NCF) encapsulating MoC/MoO2 nano dots (NDs) in a well-defined heterophase (MoC/MoO2-NCF). The MoC/MoO2 NDs were uniformly dispersed on the NCF, and the NCF limited the size of the MoC/MoO2 NDs and prevented their agglomeration, thus maximizing the electrochemically active surface area of MoC/MoO2. Moreover, the synergistic effect between the MoC/MoO2 interface and the N-defects is conducive to the full exposure of the active sites. Furthermore, theoretical calculations revealed that the MoC/MoO2 heterojunction played a unique role in modulating the electronic structure and regulating the adsorption energy of tri-iodide in the iodide reduction reaction. The MoC/MoO2-NCF CEs in DSSCs demonstrated a power conversion efficiency (PCE) of 9.92% and high durability, exceeding the PCE (8.36%) and durability of Pt CEs. Overall, this study offers insights into the controlled synthesis of high-performance Mo-based composite CE materials for DSSCs.

Electrochemical evaluations of reduced graphene oxide for efficient counter electrode in dye-sensitized solar cell

The design and development of an alternative counter electrode (CE) using graphene-based low-cost material for the dye-sensitized solar cell (DSSC) is the major motivation of the current research to replace the traditional platinum counter electrode. Herein, we prepared reduced graphene oxide (rGO) and investigated it for an efficient CE in DSSC. The structural and morphological properties of rGO are analyzed using FESEM, TEM and Raman techniques. The performance of I3- reduction on the CE is characterized by the EIS Nyquist plot, cyclic voltammetry, and the Tafel curve. The measured electrochemical results suggested that rGO CE has a lower charge transfer resistance (Rct), higher cathodic current density (Jrd), and higher Tafel slope as compared to graphene oxide (GO) CE, revealing that rGO CE has good catalytic activity towards the I3- reduction.

Bi2Se3 nanoparticles anchored MWCNTs: Counter electrode in a dye-sensitized solar cell

Anchoring of Bi2Se3 nanoparticles over ‘dip and dry’ coated multiwalled carbon nanotubes (MWCNTs) has been accomplished using a room-temperature (27 °C), inexpensive, and convenient chemical route, namely, successive ionic layer adsorption and reaction (SILAR), to yield a nanohybrid composite electrode to serve as a counter electrode (CE) in dye-sensitized solar cell (DSSC) applications. The growth of Bi2Se3 on MWCNTs has been well-tuned through varying SILAR cycles (MBSe-series) and tested as counter electrodes (CEs) with reference to MWCNTs and Bi2Se3 in FTO/ZnO/Eosin-Y/Iodide-triiodide/Counter electrode/FTO assembly. Grown CEs have been validated through XRD, XPS, Raman, FTIR, and FESEM studies, while the assembled DSSCs have been assessed through JV, EQE, EIS, and electrochemical stability studies. Well-optimized Bi2Se3/MWCNTs nanohybrid composites have been used as CEs in DSSCs and showed superior device performance (0.52 %) compared to bare MWCNTs (0.14 %) and Bi2Se3 (0.09 %) due to the well-anchored Bi2Se3 over one-dimensional MWCNTs through a large number of synergistic electrochemical active sites. A DSSC fabricated with MBSe-12 as the CE exhibits enhanced stability compared to bare Bi2Se3 and MWCNTs. Also, it reveals a charge transfer resistance of 7.92 Ω/cm2 and an electron lifetime of 16 μs, yielding a maximum efficiency of 0.52 % and an external quantum efficiency of 28.20 %.

Magnetic field modulation effect of photoelectric properties in dye-sensitized solar cells with La0.67(Ca,Ba)0.33MnO3 as counter electrodes.

In recent years, many semiconductor materials with unique band structures have been used as Pt counter electrode (CE) substitutes for dye-sensitized solar cells (DSSCs), which makes the photoelectric properties of DSSCs possible to be modulated by electric field, magnetic field, and light field. In this work, La0.67(Ca Ba)0.33MnO3 (LCBMO) thin film is employed to act as CE in DSSCs. The experimental results indicate that short-circuit current density and photoelectric conversion efficiency present better stability when applying an external magnetic field to the DSSCs. Furthermore, both the exchange current density (J0) and limit diffusion current density (Jlim) are largely enhanced by an external magnetic field. J0 increases from -0.51 mA•cm-2 to -0.65 mA•cm-2, and Jlim increases from 0.2 mA•cm-2 to 0.3 mA•cm-2 when applying a magnetic field of 0.25 T. The fitting results of the impedance test verify that the magnetic field reduces the value of Rct. Both magnetic-field enhancing catalytic activity and CMR effect jointly promote the increase of photocurrent and finally improve the photovoltaic effect in DSSCs.

In-situ electropolymerization of congo red-doped polypyrrole and gold nanoparticle nanocomposites and its electrocatalytic application

A one-step electrochemical approach has been utilized to synthesize congo-red doped polypyrrole film embedded with gold nanoparticles (PPy-CR-AuNP). This study discusses for the first time the electrocatalytic properties of PPy-CR and PPy-CR-AuNP as counter-electrode in dye-sensitized solar cell (DSSC). Physicochemical characterizations of the films with and without AuNP have been presented. Both films/electrodes displayed excellent charge transfer abilities, as demonstrated by cyclic voltammetry analysis. Notably, PPy-CR-AuNP exhibited enhanced electron transfer kinetics with a 17% increase in electroactive surface area and improved efficiency in the I−/I3− redox pair activity compared to PPy-CR. Following extended storage under ambient conditions, PPy-CR-AuNP maintained a better mass transport and electron transfer at the electrode-electrolyte interface. The DSSC employing PPy-CR-AuNP as counter electrode exhibited a 12.5% enhancement in efficiency, lower electron transport time, higher electron recombination time and electron collection efficiency of up to 89%. Moreover, the electron decay rate was found to be 12.5% lower compared to the DSSC with PPy-CR electrode. These results demonstrated that PPy-CR-AuNP is an appropriate candidate for DSSC.

A novel Pt-free counter electrode based on MoSe2 for cost effective dye-sensitized solar cells (DSSCs): Effect of Ni doping

In this study, we propose a new counter electrode based on the Ni-doped MoSe2 as a viable counter electrode for DSSC applications. We investigate different ratios of Ni dopant inside the MoSe2 lattice. Our results show that the introduction Ni can increase the active surface area and improve the electrocatalytic behavior of the MoSe2 materials. We employed our prepared materials as the counter electrode in DSSCs and show that our optimized case demonstrates an open circuit voltage of 688 mV, a short circuit current density of 16 mA/cm2, a fill factor of 63% resulting an efficiency of 6.94% which is a significant improvement from the 6.68% efficiency of the DSSCs fabricated from the high-cost platinum counter electrode.

Phase-Selective Synthesis of Cobalt Sulfide Heterostructure Catalysts as Efficient Counter electrodes in Dye-Sensitized Solar Cells.

Developing a cost-saving, high-efficiency, and simple synthesis of counter electrode (CE) material to replace pricy Pt for dye-sensitized solar cells (DSSCs) has become a research hotspot. Owing to the electronic coupling effects between various components, semiconductor heterostructures can significantly enhance the catalytic performance and endurance of counter electrodes. However, the strategy to controllably synthesize the same element in several phase heterostructures used as the CE in DSSCs is still absent. Here, we fabricate well-defined CoS2/CoS heterostructures and use them as CE catalysts in DSSCs. The as-designed CoS2/CoS heterostructures display high catalytic performance and endurance for the triiodide reduction in DSSCs thanks to the combined and synergistic effects. As a result, a DSSC with CoS2/CoS achieves a high power conversion efficiency of 9.47% under illumination, surpassing that of pristine Pt-based CE (9.20%). Besides, the CoS2/CoS heterostructures possess a quick activity initiation process and extended stability, broadening their potential applications in various areas. Therefore, our proposed synthetic approach could offer new insights for synthesizing functional heterostructure materials with improved catalytic activities in DSSCs.

Metal-Free Counter Electrodes for DSSCs Based on Nitrogen-Doped Reduced Graphene Oxide Materials

The importance of counter electrodes in Dye Sensitized Solar Cells (DSSCs) cannot be neglected as they enable the transfer of electrons across the outer circuit, thereby facilitating the reduction reaction of the I3−/I− redox electrolyte. However, the dissolution and deposition of the usual platinum layer on the counter electrode has resulted in contamination concerns. To address this issue, metal-free counter electrodes made of reduced graphene oxide (rGO) aerogels were developed and their catalytic performance towards I3− reduction was evaluated. The reduced graphene materials were characterized, and the fitting analysis of XPS revealed the presence of various nitrogen species, with the primary peaks attributed to pyridinic and pyrrolic nitrogen. The hydrothermal treatment of graphene oxide (GO) resulted in a higher graphitic character and the intensification of the contacts between graphene nanosheets, which should entail higher electrical conductivity, both in-plane and between rGO sheets. Additionally, the presence of nitrogen-provided active sites promoted the catalytic reduction of the electrolyte. Encouragingly, good charge transfer rates were observed between the counter electrode and the electrolyte in the assembled DSSCs, resulting in good photocurrents and exceptional stability over the course of nearly 1200 h after cell assembly. The results obtained suggest that these GO-based systems are promising candidates for developing metal-free counter electrodes for DSSC, supporting the interest of further study.

PtSe2 outperforms Pt as a counter electrode in dye sensitized solar cells

In the present study, we show that PtSe2 films, prepared by soft selenization of pre-deposited Pt, is a very efficient counter electrode (CE) in dye sensitized solar cells (DSSCs). Devices based on PtSe2 achieve better photoconversion efficiency (9.5 ± 1.2%) than those employing bare Pt CE (9.18 ± 0.21%), even if the latter use three times more Pt loading than that used to prepare the PtSe2 CE. Films with of various Pt loadings have been prepared by electrodeposition and their catalytic properties have been investigated and compared with films of corresponding Pt loading which have been transformed to PtSe2 by low-temperature selenization. The improved performance of the PtSe2 CEs has been assigned to the higher availability of catalytic active sites and the more effective mechanism of interfacial electron transfer. This is a first attempt to explore the role of PtSe2 as the CE in DSSCs. The strong advantages of PtSe2 in relation to catalytic activity, stability, efficiency, combined with cost reduction, due to the lower mass loading required for a given performance, renders this noble-transition metal dichalcogenide a promising candidate to boost the performance of third generation photovoltaics, opening-up possibilities, at the same time, for other applications where Pt is used as the catalyst.