Electrodes For Dye-sensitized Solar Cells Research Articles

Nano tumbleweed-like tungsten disulfide as a viable surrogate for platinum counter electrodes in dye-sensitized solar cells

Tungsten disulfide (WS2), a notable member of the transition metal dichalcogenides family, has emerged as a promising candidate for energy storage and conversion applications. In this study, WS2 was synthesized via a hydrothermal method using sodium tungstate and thiourea as precursor materials, with hydroxylamine hydrochloride as the reducing agent and cetyl trimethyl ammonium bromide as a surfactant. The primary objective was to develop a cost-effective, easily synthesized, and scalable material capable of replacing platinum (Pt) in dye-sensitized solar cells (DSSCs), where Pt is both prohibitively expensive and scarce. Characterization of the synthesized WS2 was conducted through a range of physical analyses, including SEM, TEM, XRD, EDAX, FTIR, and Raman spectroscopy, which provided compelling evidence for the formation of a unique nano-tumbleweed-like structure of WS2. When used as a counter electrode (CE), the synthesized WS2 exhibited exceptional photocatalytic activity, resulting in a commendable power conversion efficiency (PCE) of 12.06 % when coupled with fluorine-doped tin oxide (FTO) plates coated with TiO2 as the photoanode, N719 as the dye, and Iˉ/I3ˉ as the liquid electrolyte. Additionally, the fabricated device underwent comprehensive electrical characterization, including cyclic voltammetry (CV), current-voltage (IV) measurements, electrochemical impedance spectroscopy (EIS), and Tafel analysis, revealing properties similar to those of Pt counter electrodes. Notably, WS2 demonstrated an open-circuit potential of 852 mV and a short-circuit current density of 28 mA/cm2, accompanied by a fill factor of 0.43 and a commendable lifetime of 15.92 ms.

Microwave-plasma surface modification of nanostructured-polyaniline:graphite composite counter electrode in dye-sensitized solar cells

This work demonstrates microwave plasma surface modifications of nanostructured polyaniline (NPES)-based counter electrodes (CE). Oxidative oxygen (O2) plasma and reductive hydrogen (H2) plasma were used in this study. Optical emission spectra confirm the presence of reactive species in both plasmas through the emissive species, such as O2+, O+, O•, H(nl), and H2 Fulcher-α. Microwave plasma treatment does not affect the surface morphology of NPES composite CE, which conserves its granule nanostructures, as revealed by SEM. The water contact angle measurements demonstrate how the O2 plasma treatment improves surface hydrophilicity, contrary to the H2 plasma treatment. Raman spectroscopy results show significant changes in the intrinsic-oxidation state and the number of semiquinonoid species (SQ) of NPES after plasma treatments, which are represented by the ratios of Raman intensity at 1368–1260 cm−1 and 1624–1583 cm−1, respectively. Generally, O2 plasma treatment increases the intrinsic-oxidation state and SQ number, opposite to the H2 plasma. The optimum condition of microwave plasma-assisted surface modification was attained in one minute of O2 plasma treatment, producing NPES with the highest intrinsic-oxidation state and SQ number. A power conversion efficiency of 3.17 % was obtained by a dye-sensitized solar cell fabricated with a modified CE using a one-minute O2 plasma treatment.

Design highly effective B or N doped mesoporous carbon fibers catalysts for I3-/I- redox couple regeneration in carbon-based dye-sensitized solar cells

Construction of mesoporous structure and improving the conductivity of carbon counter electrode are feasible paths to enhance the catalytic activity in dye-sensitized solar cells (DSCs) toward the I3-/I- redox couple regenerating (IRR). Herein, mesoporous carbon fiber (PCf) has been first synthesized and the DSCs using PCf counter electrode results in a power conversion efficiency (PCE) of 7.12%, significantly surpassing the PCE of 6.01% generated by the DSCs with carbon fiber (Cf) counter electrode without mesoporous structure. Additionally, doping with heteroatoms B or N can further enhance the catalytic performance of PCf. Consequently, B or N doped Cf (BPCf or NPCf) counter electrode-based DSCs achieve high PCE values of 8.43% and 7.96%, respectively, demonstrating PCE improvements of 40.3% and 32.4%. This enhancement in catalytic activity for IRR in DSCs can be first attributed to the increased specific surface area of Cf which can provide more catalytic activated sites. Meanwhile, the enhanced conductivity of PCf by heteroatoms B or N doping is also an important factor for the improved catalytic activity. This work is expected to provide potential path to enhanced the catalytic activity of carbon counter electrode in DSCs toward IRR.

Preparation of a hierarchical porous activated carbon derived from cantaloupe peel/fly ash/PEDOT:PSS composites as Pt-free counter electrodes of dye-sensitized solar cells

Hierarchical porous activated carbon/fly ash/PEDOT:PSS composites (AC:FA) for a counter electrode (CE) were created using a doctor blade technique and applied in dye sensitized solar cells. Hierarchical porous activated carbon (AC) was produced using a potassium hydroxide (KOH) activation process from cantaloupe peels (Cucumis melo L. var. cantaloupensis). AC was introduced into fly ash at various mass ratios to enhance several physical and electrochemical characteristics. Compared to bare FA, the AC:FA electrode displayed a high electrocatalytic activity for the iodide/triiodide redox (I−/I3−) reaction. The test findings show that a higher proportion of AC has an impact on a CE's catalytic activity and charge transfer resistance. The power conversion efficiency (PCE) of the dye-sensitized solar cell (DSSC) attained 5.81 % using the AC:FA CE with AC in a mass ratio of FA in 3:1 (wt./wt.), which is very near the performance of manufactured DSSC's with a platinum (Pt)-based CE (5.91 %). The AC:FA CE stands out as a strong candidate to substitute for costly Pt CEs due to its enhanced electrochemical activity and charge transfer capabilities obtained with an inexpensive and simple production procedure.

Ni-Mo bimetallic oxides/rGO nanocomposites as counter electrode for the application of DSSCs

The one-pot chemical reduction process was used to generate the bimetallic Ni–Mo nanoparticles attached to reduced graphene oxide (rGO) nanocomposite, which was then used as an effective counter electrode in dye-sensitized solar cells (DSSC). Diffraction patterns were used to investigate the face-centered crystalline structure of the spherical-shaped Ni–Mo nanoparticles that were uniformly anchored over the surface of rGO. The nanoparticles had an average diameter ranging from 70 to 120 nm. Raman spectroscopy was utilized to investigate the structural interaction that was created by the presence of bimetallic nanoparticles and the graphene oxide support. In addition, the rGO/Ni–Mo counter electrode equipped DSSC demonstrated the highest solar to electrical energy conversion efficiency of 3.11% under irradiation from one sun with a fill factor (FF) of 0.48.

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.

Size-Controlled Cu3VSe4 Nanocrystals as Cathode Material in Platinum-Free Dye-Sensitized Solar Cells.

In this work, we report the first single-step, size-controlled synthesis of Cu3VSe4 cuboidal nanocrystals, with the longest dimension ranging from 9 to 36 nm, and their use in replacing the platinum counter electrode in dye-sensitized solar cells. Cu3VSe4, a ternary semiconductor from the class of sulvanites, is theoretically predicted to have good hole mobility, making it a promising candidate for charge transport in solar photovoltaic devices. The identity and crystalline purity of the Cu3VSe4 nanocrystals were validated by X-ray powder diffraction (XRD) and Raman spectroscopy. The particle size was determined from the XRD data using the Williamson-Hall equation and was found in agreement with the transmission electron microscopy imaging. Based on the electrochemical activity of the Cu3VSe4 nanocrystals, studied by cyclic voltammetry, the nanomaterials were further employed for fabricating counter electrodes (CEs) in Pt-free dye-sensitized solar cells. The counter electrodes were prepared from Cu3VSe4 nanocrystals as thin films, and the charge transfer kinetics were studied by electrochemical impedance spectroscopy. The work demonstrates that Cu3VSe4 counter electrodes successfully replace platinum in DSSCs. CEs fabricated with the Cu3VSe4 nanocrystals having an average particle size of 31.6 nm outperformed Pt, leading to DSSCs with the highest power conversion efficiency (5.93%) when compared with those fabricated with the Pt CE (5.85%).

A low-cost, activated carbon-coated, stainless-steel counter electrode for dye-sensitized solar cells

A low-cost, activated carbon (AC) and sugar-coated stainless-steel counter electrode for dye-sensitized solar cells was successfully fabricated and characterized. For performance comparison, a similar electrode was fabricated using a FTO glass as the substrate. The photovoltaic performance of dye-sensitized solar cells made with these two counter electrodes were compared with solar cells made with a Pt counter electrode. The optimized, activated carbon-coated, stainless-steel-based dye-sensitized solar cells showed an energy conversion efficiency of 8.21% while similarly optimized solar cells made with activated carboncoated FTO counter electrode showed an efficiency of 7.50%. The efficiency of corresponding solar cells made with Pt counter electrode was 9.22%. The high solar cell efficiency of 89% of that of Pt based cells can be attributed to the high electro-catalytic activity and enhanced effective surface area of activated carbon/ sugar composite and good electrical conductivity of stainless steel as demonstrated by electrochemical impedance spectroscopy, cyclic voltammetry, Tafel plot analysis and SEM imaging.

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.

Construction of Cu-doped α-MoO3 nanostructures and their application as counter electrode in dye-sensitized solar cells

The proposed work was to develop a low-cost counter electrode used in dye-sensitized solar cells (DSSCs) for the replacement of Ptelectrodes. Alpha Molybdenum oxide (α-MoO3) and copper-doped α-MoO3 (Cu-doped α-MoO3) were prepared by a hydrothermal technique. The physical properties and performance of DSSCs were investigated by varying Cu doping (0.05%, 0.1%, and 0.2% wt.) with α-MoO3. DSSC fabricated with Cu-doped α-MoO3 was found to be 2.87% (S3) efficiency, which was higher than that of undoped α-MoO3 (1.83%) and platinum (2.51%) as counter electrodes (CEs). The results clearly indicate that Cu-doped α-MoO3 can effectively replace expensive platinum CEs in a cost-efficient manner.

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%.

Efficient processed carbon Soot@MoS2 hybrid Bi-functional electrode for dye-sensitized solar cell and asymmetric supercapacitor devices

A feasible approach to rectify the world's energy demand using sustainable development of adequate energy generation and storage technologies in a single channel. In this respect, we made a holistic approach with a bi-functional electrode material to perform effectively in energy generation and storage applications. MoS2 nanosheets were produced by the eco-friendly method and reduced graphene oxide is used to prepared by carbon soot which is derived from castor oil. The prepared soot and rGO were combined with MoS2 nanosheets using a simple sonication method. The as-prepared sample was introduced in the supercapacitor and DSSC application. The combination MoS2@rGO provides an enhanced conversion efficiency of 11.81 ​% and the reproducibility of DSSC is also studied. Further, MoS2@rGO is used to fabricate an asymmetric supercapacitor to investigate its real-time application. The device produced the maximum power density (1666.6 ​mW/kg) and energy density (25.69 ​mWh/Kg) at 1 A/g. The asymmetric supercapacitor device holds a cyclic stability of 81.4 % for 5000 cycles and it powered up an LED device for 4 ​min.

N, S Co-doped carbon-encapsulated CoS(Co9S8) hybrid counter electrodes for dye-sensitized solar cells

N, S Co-doped carbon-encapsulated CoS(Co9S8) hybrid counter electrodes for dye-sensitized solar cells

In situ grown Bi2WO6@CoMoO4 layered cladding structure on carbon nanofibers by a two-step solvothermal method and Ti mesh substrate as advanced counter electrodes for dye-sensitized solar cells.

Based on carbon nanofibers (CNFs) with excellent electrical conductivity, a three-layer cladding structure CNFs@Bi2WO6@CoMoO4 material was prepared by a two-step solvothermal method, which effectively combines the great catalytic ability of transition metal oxides with the good conductivity of CNFs. Titanium (Ti) mesh was used as the conductive substrate and CNFs@Bi2WO6@CoMoO4 was scraped on it to prepare paired counter electrodes (CEs), and then dye-sensitized solar cells (DSSCs) were assembled by unifying with photoanode and iodine electrolyte. The photoelectric conversion efficiency (PCE) of 9.41% (with Voc of 0.784 V, Jsc of 17.90 mA cm-2 and FF of 0.72) was obtained under standard light conditions (AM 1.5 G). In brief, this study found a cheaper and better alternative material for Pt and also provides more possibilities for the selection of conductive substrate for CEs.

Fabrication of TiO2-Ag composites for working electrode of dye-sensitized solar cells

A solar cell is a device that can convert solar energy into electrical energy. The third generation of solar cells is Dye-Sensitized Solar Cells (DSSC). Typically, DSSC consists of a working electrode (semiconductive metal oxide), a photosensitizer, an electrolyte, and a counter electrode (platinum or carbon electrode). Among the components, a working electrode is one of the crucial components to control the electrochemical performance. This study examines variations in Ag composition in TiO2-Ag composites against efficiency using two materials and fabrication methods. First, using the solid-state method, TiO2-Ag composites were fabricated from Ag paste and TiO2 paste. The highest efficiency results were achieved at TiO2 N-RT + Ag 1%. The efficiency increased from 1.05% to 1.51% compared to TiO2 without Ag doping. Second, using the solvothermal method, TiO2-Ag composites were fabricated from AgNO3 and TiO2 particles. The highest efficiency results were obtained at TiO2 NP + Ag 0.75%. The efficiency increased from 0.82% to 1.07% compared to TiO2 without Ag doping. Furthermore, the material with the best efficiency was characterized using FTIR, XRD, and SEM to identify the material’s functional groups, phases, and morphology, respectively.

PEDOT-based counter electrodes for dye-sensitized solar cells: rigid, flexible and indoor light applications

This review presents the importance and applications of poly(3,4-ethylenedioxythiophene) (PEDOT) as a catalyst in dye-sensitized solar cell. Emphasis is on composite materials with better performances for rigid, flexible, and indoor uses.

Kinetics of Charge Transfer at Carbon-Based Counter Electrodes for Dye-Sensitized Solar Cells with Aqueous Electrolytes

Dye-sensitized solar cells (DSSCs) might provide a highly sustainable alternative for next generation photovoltaics. This is due to their low-energy production from abundant materials, short energy payback time, high efficiency under low illumination intensities (i.e., diffuse light or indoor conditions), and versatile concepts of applications. However, some commonly used electrolyte components are environmentally problematic. Acetonitrile or other volatile organic solvents, e.g., as well as carcinogenic cobalt complexes should not leak from DSSCs. Sealing foils, however, which are typically used to prevent such leakage, carry a risk of long-term failure.Replacing the organic solvent by water offers several advantages, as it is environmentally benign, less volatile and the cell function, further, cannot be damaged by the intrusion of water vapor. Instead of Co-complexes, e.g., the stable organic radical TEMPO (2,2,6,6-tretramethylpiperidine-1-oxyl) can serve as an alternative redox mediator with a highly positive redox potential (0.71 V vs. NHE). Using TEMPO, power conversion efficiencies (PCE) of up to 4.3% and high open-circuit voltages (V oc = 0.955 V) have been reported.[1] However, the use of TEMPO is limited by its solubility in water (C max < 0.15 M). Its derivative 4-hydroxy-TEMPO (OH-TEMPO) possesses a significantly higher solubility in water (C max > 2 M) and a more positive redox potential (0.81 V vs. NHE), making it a promising candidate as a redox mediator.In this work, we built DSSCs with TEMPO and OH-TEMPO based aqueous electrolytes, Y123-sensitized TiO2 photoanodes, and counter electrodes coated with poly(3,4-ethylenedioxythiphene) (PEDOT). For OH-TEMPO, the short-circuit current density (j sc) and open-circuit voltage were higher than with TEMPO, but the fill factor (FF) and the PCE were significantly lower. By impedance studies, large charge transfer resistances at the counter electrode (R CE) were obtained for OH-TEMPO in combination with additives such as 1-methylbenzimidazole (MBI), indicating a strong kinetic limitation of the OH-TEMPO+ reduction. However, we found that such additives as MBI or other organic compounds, are necessary to suppress recombination at the photoanode/electrolyte interface. Thus, we subsequently studied different counter electrode materials, such as platinum (reference), conducting polymers, and carbon materials, in contact to OH-TEMPO electrolytes with MBI to determine R CE and find suitable materials for the application in DSSCs.[1] Yang, W., Söderberg, M., Eriksson, A. I. K. & Boschloo, G. Efficient aqueous dye-sensitized solar cell electrolytes based on a TEMPO/TEMPO+ redox couple. RSC Advances 5, 26706–26709 (2015).

Innovative PANI/g-C3N4@rGO nanocomposite electrode for improved energy storage and conversion applications

We successfully synthesized a ternary conducting polymer nanocomposite using an in-situ oxidative polymerization method, incorporating polyaniline, graphitic carbon nitride, and reduced graphene oxide. This nanocomposite serves as a bifunctional electrode for applications in energy storage and conversion. The as-prepared PANI nanocomposite exhibited excellent storage properties, with a specific capacitance of 442 F/g in 1 M H2SO4 as an electrolyte in the presence of graphitic-C3N4@reduced graphene oxide. This is a significant enhancement over the specific capacitance of pure PANI, which is typically∼200 F/g. Interestingly, the PANI/graphitic-C3N4@reduced graphene oxide electrode exhibited better cycling stability with 90% retention of the specific capacitance after 5000 cycles at a current density of 2.5 A/g. Furthermore, when employed as a counter electrode for dye-sensitized solar cells (DSSC), it exhibits excellent electrocatalytic activity, which is attributed to its large specific surface area and superior electrocatalytic activity. The dye-sensitized TiO2 photoanodes were sandwiched between CEs using a PEO-based gel electrolyte, and photovoltaic studies were performed under simulated illumination of 100 mW/cm2. The dye sensitized solar cell exhibited the short circuit current density (Jsc) 13.5 mA/cm2 and open circuit voltage (Voc) 0.76 V with power conversion efficiency of 6 %.