Dye sensitized solar cell based on platinum decorated multiwall carbon nanotubes as catalytic layer on the counter electrode

In this study we have employed multiwall carbon nanotubes (MWCNT), decorated with platinum as catalytic layer for the reduction of tri-iodide ions in dye sensitized solar cell (DSSC). MWCNTs have been prepared by a simple one step pyrolysis method using ferrocene as the catalyst and xylene as the carbon source. Platinum decorated MWCNTs have been prepared by chemical reduction method. The as prepared MWCNTs and Pt/MWCNTs have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). In combination with a dye adsorbed TiO₂ photoanode and an organic liquid electrolyte, Pt/MWCNT composite showed an enhanced short circuit current density of 16.12 mA/cm² leading to a cell efficiency of 6.50% which is comparable to that of Platinum.     

Preparation and properties of a carbon nanotube-based nanocomposite photoanode for dye-sensitized solar cells

This study fabricates dye-sensitized solar cells (DSSCs) based on TiO(2)/multi-walled carbon nanotube (MWCNT) nanocomposite photoanodes obtained by the modified acid-catalyzed sol-gel procedure. Results show that incorporating MWCNTs into a TiO(2)-based electrode efficiently improves the physicochemical properties of the solar cell. The results of dye adsorption and cell performance measurements indicate that introducing MWCNTs would improve the roughness factor (from?834 to?1267) of the electrode and the charge recombination of electron/hole (e(-)/h(+)) pairs. These significant changes could lead to higher adsorbed dye quantities, photocurrent and DSSC cell performance. Nevertheless, a higher loading of MWCNTs causes light-harvesting competition that affects the light adsorption of the dye-sensitizer, and consequently reduces the cell efficiency. This study suggests an optimum MWCNT loading in the electrode of 0.3?wt%, and proposes a sol-gel synthesis procedure as a promising method of preparing the TiO(2)-based nanocomposite.     

Fabrication and properties of meso-macroporous electrodes screen-printed from mesoporous titania nanoparticles for dye-sensitized solar cells

A meso-macroporous TiO₂ film electrode was fabricated by using mesoporous TiO₂ (m-TiO₂) nanoparticles through a screen-printing technique in order to efficiently control the main fabrication step of dye-sensitized solar cells (DSSCs). The qualities of the screen-printed m-TiO₂ films were characterized by means of spectroscopy, electron microscopy, nitrogen adsorption–desorption and photoelectrochemical measurements. Under the optimal paste composition and printing conditions, the DSSC based on the meso-macroporous m-TiO₂ film electrode exhibits an energy conversion efficiency of 4.14%, which is improved by 1.70% in comparison with DSSC made with commercially available nonporous TiO₂ nanoparticles (P25, Degussa) electrode printed with a similar paste composition. The meso-macroporous structure within the m-TiO₂ film is of great benefit to the dye adsorption, light absorption and the electrolyte transportation, and then to the improvement of the overall energy conversion efficiency of DSSC.     

Carbon nanotube-enhanced photoelectrochemical properties of metallo-octacarboxyphthalocyanines

The photoelectrochemistry of metallo-octacarboxyphthalocyanines (MOCPc, where M = Zn or Si(OH)₂) integrated with MWCNTs for the development of dye-sensitized solar cells (DSSCs) is reported. The DSSC performance (obtained from the photo-chronoamperometric and photo-impedimetric data) decreased as ZnOCPc > (OH)₂SiOCPc. The incorporation of the MWCNTs on the surface of the TiO₂ film (MOCPc–MWCNT systems) gave higher photocurrent density than the bare MOCPc complexes. Also, from the EIS results, the MOCPc–MWCNT hybrids gave faster charge transport kinetics (approximately three times faster) compared to the bare MOCPc complexes. The electron lifetime was slightly longer (ca. 6 ms) at the ZnOCPc systems than at the (OH)₂SiOCPc system (ca. 4 ms) meaning that the presence of the MWCNTs on the surface of the TiO₂ film did not show any significant improvement on preventing charge recombination process.     

Optimization of the cutting process of multi-wall carbon nanotubes for enhanced dye-sensitized solar cells

Dye-sensitized solar cells (DSSCs) were fabricated based on multi-wall carbon nanotube (MWCNT)-TiO₂ photo-anodes, which were prepared by the procedures of cutting MWCNTs and subsequent immobilization TiO₂ on MWCNTs. Through a detailed study, we found that cut-MWCNTs with proper ultrasonication time (2 h) and proper content (0.075%) resulted in 58 and 40% increase in short-circuit photocurrent and overall energy conversion efficiency, respectively, compared with that of a DSSC using only TiO₂ photo-anode. The enhancement of cut-MWCNTs for DSSC was attributed to the introduction of percolative conductive paths which facilitate the rapid electron transfer.     

Preparation and characterization of (100 − x) TiO<Subscript>2</Subscript> + (x)ZnO nanocomposites for dye-sensitized solar cells using <Emphasis Type="Italic">Beta vulgaris</Emphasis> and <Emphasis Type="Italic">Syzygium cumini</Emphasis> natural dye extract

The present paper attempts to report the preparation of TiO₂–ZnO nanocomposite photoanode materials for dye-sensitized solar cells (DSSC) and analyse the efficiency of DSSC with natural dyes. The structural and optical characteristics of the composites were studied by transmission electron microscopy, X-ray diffraction, field effective scanning electron microscopy, energy dispersive spectrometry, photoluminescence and absorption spectroscopy. The synthesized nanocomposites formed on FTO substrates are applied as photoanode in a dye-sensitized solar cell (DSC). The natural dyes extracted from Beta vulgaris (Beetroot) and Syzygium cumini (black plum) were used in the fabrication of DSSC. The solar cells’ photovoltaic performance in terms of short-circuit current, open circuit voltage, fill factor and energy conversion efficiency was tested with photocurrent density–voltage measurements. The evolution of the solar cells parameters is explored as a function of the photoanode and type of dye used in DSSC fabrication.The obtained results show that the efficiency of DSSC significantly changes with the addition of ZnO to TiO_2, while the Beta vulgaris dye has evidently shown higher photo sensitized performance compared to Syzygium cumini in the preparation of DSSC.     

Fabrication of alizarin red S/multi-walled carbon nanotube nanocomposites and their application in hydrogen peroxide detection

In this work, an easy and effective method to synthesize alizarin red S/multi-walled carbon nanotube (ARS/MWCNT) nanocomposites based on the π–π stacking non-covalent interactions between ARS and MWCNTs was introduced. The characters of ARS/MWCNT nanocomposites were investigated by Fourier transformation infrared spectroscopy, UV–Vis spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscope, and electrochemical techniques. ARS tightly coating on MWCNTs surface makes the nanocomposites good dispersibility in water and excellent electrochemical activity. Because of the combination of the excellent electroactivity of ARS and the unique properties of MWCNTs, ARS/MWCNT nanocomposites-modified glassy carbon electrode exhibits a good response to the reduction of hydrogen peroxide and takes on a promising prospect of the practical application in electrochemical sensors field.     

Ultrafast Flame Annealing of TiO2 Paste for Fabricating Dye‐Sensitized and Perovskite Solar Cells with Enhanced Efficiency

Mesoporous TiO₂ nanoparticle (NP) films are broadly used as electrodes in photoelectrochemical cells, dye‐sensitized solar cells (DSSCs), and perovskite solar cells (PSCs). State‐of‐the‐art mesoporous TiO₂ NP films for these solar cells are fabricated by annealing TiO₂ paste‐coated fluorine‐doped tin oxide glass in a box furnace at 500 °C for ≈30 min. Here, the use of a nontraditional reactor, i.e., flame, is reported for the high throughput and ultrafast annealing of TiO₂ paste (≈1 min). This flame‐annealing method, compared to conventional furnace annealing, exhibits three distinct benefits. First, flame removes polymeric binders in the initial TiO₂ paste more completely because of its high temperature (≈1000 °C). Second, flame induces strong interconnections between TiO₂ nanoparticles without affecting the underlying transparent conducting oxide substrate. Third, the flame‐induced carbothermic reduction on the TiO₂ surface facilitates charge injection from the dye/perovskite to TiO₂. Consequently, when the flame‐annealed mesoporous TiO₂ film is used to fabricate DSSCs and PSCs, both exhibit enhanced charge transport and higher power conversion efficiencies than those fabricated using furnace‐annealed TiO₂ films. Finally, when the ultrafast flame‐annealing method is combined with a fast dye‐coating method to fabricate DSSC devices, its total fabrication time is reduced from over 3 h to ≈10 min.     

PEDOT基对电极染料敏化太阳能电池研究进展

染料敏化太阳能电池(DSSC)是新型太阳能电池的研究热点之一,其优异的弱光发电性能被不断探索,同时透明及柔性DSSC在可穿戴设备上的应用也与日俱增。DSSC的循环依靠对电极的作用才能及时高效地完成,因此对电极材料的选择尤为关键。近几年研究者们对对电极材料的研究不断深入,其中可作为DSSC对电极材料使用的高分子导电聚合物聚3,4-乙撑二氧噻吩(PEDOT)因其高导电性、对电解质的催化能力、透明性和柔性等特点受到广泛关注。以含PEDOT或掺杂PEDOT对电极的DSSC为对象,阐述了PEDOT对电极的制备方法,并总结了近几年PEDOT作为DSSC对电极的研究进展。在此基础上,提出未来在电池效率突破研究中应以原位聚合法制备PEDOT对电极为主,以及在大规模工业化生产中应以物理涂覆法为主的观点,为PEDOT对电极DSSC的研究提供依据。     

Effects of mesoscopic poly(3,4-ethylenedioxythiophene) films as counter electrodes for dye-sensitized solar cells

Counter electrode coated with chemically polymerized poly(3,4-ethylenedioxythiophene) (PEDOT) in a dye-sensitized solar cell (DSSC) was studied. The surface morphology and the nature of I⁻/I₃⁻ redox reaction based on PEDOT film were investigated using Atomic Force Microscopy and Cyclic Voltammetry, respectively. The performance of the DSSCs containing the PEDOT coated electrode was compared with sputtered-Pt electrode. We found that the root mean square roughness decreases and conductivity increases as the molar ratio of imidazole (Im)/EDOT in the PEDOT film increases. The DSSC containing the PEDOT coated on fluorine doped tin oxide glass with Im/EDOT molar ratio of 2.0, showed a conversion efficiency of 7.44% compared to that with sputtered-Pt electrode (7.77%). The high photocurrents were attributed to the large effective surface area of the electrode material resulting in good catalytic properties for I₃⁻ reduction. Therefore, the incorporation of a multi-walled carbon nanotube (MWCNT) in the PEDOT film, coated on various substrates was also investigated. The DSSC containing the PEDOT films with 0.6 wt.% of MWCNT on stainless steel as counter electrode had the best cell performance of 8.08% with short-circuit current density, open-circuit voltage and fill factor of 17.00 mA cm⁻², 720 mV and 0.66, respectively.     

Optimization of TiO<Subscript>2</Subscript>/MWCNT composites for efficient dye sensitized solar cells

This paper deals with the effects of introducing multiwall carbon nanotubes (MWCNTs) into photoanodes of dye sensitized solar cells (DSSCs). Mesoporous titanium dioxide (TiO₂) nanoparticles were synthesized using sol–gel technique. TiO₂/MWCNT composites were prepared by adding functionalized MWCNTs to TiO₂ nanoparticles using two different surfactants (α-terpineol and Triton X-100). Nanoparticles and composites were characterized using Dynamic Light Scattering spectrophotometer, Raman spectrometer, X-ray diffractometer, field emission scanning electron microscope, Brunauer–Emmett–Teller surface area analyzer and UV–Vis spectrophotometer. FESEM depicted that particles were spherical in shape and their size decreased due to addition of MWCNTs. This was attributed to the decrease in the crystallite size which in turn confirmed by XRD. UV–Vis absorption spectra showed the better absorbance for the visible range of light, as the content of MWCNT is increased. From the Tauc plot optical band gap was calculated and noted that it declined gradually with the content of MWCNTs. BET surface area increased drastically which was attributed to the formation of more number of pores in the nanocomposites as visualized from FESEM. UV–Vis spectra of dye desorbed from the photoanode revealed that the dye adsorption increased as a function of MWCNT wt%. I–V studies were carried out under the illumination of 100 mW/cm² simulated sunlight. Photoanodes prepared by both the methods showed better performance compared to pristine TiO₂ photoanode, because of high conducting path and high surface area provided by MWCNTs. Photoanodes with 0.19 wt% MWCNTs in them were able to achieve maximum efficiency of 3.54 and 3.86% for method A and B respectively.     

Design and development of electronic- and micro-structures for multi-functional working electrodes in dye-sensitized solar cells

This paper outlines a new strategy to optimize the performance of electrodes in dye-sensitized solar cells (DSSCs), through the engineering of electronic structures in conjunction with the micro-structures of the devices. We propose a simple hydrolysis method for the fabrication of a family of quasi-core–shell TiO₂ (hydrolysis)/PbS composites for working electrodes. Measurements confirm a shift in absorption from the UV to visible range. We also measured cell performance, including short-circuit photocurrent, open-circuit photovoltage, and the power conversion efficiency (η) of DSSCs. The obtained η of DSSC (6.05%) with a TiO₂ (P-25)/TiO₂ (hydrolysis) + 0.005 M PbS electrode is substantially higher than that of the conventional DSSC (5.11%) with a TiO₂ (P-25) electrode, due to improved p–n junctions, light-scattering, and light absorption. Finally, the shell of TiO₂ (hydrolysis) protected the core of PbS from the corrosive effects of electrolytes, thereby prolonging the life span of the DSSC. This novel approach to electrode design could lead to advances in DSSC as well as other energy applications including photo-catalysis technology.     

Dye sensitized solar cell of TiO2 nanoparticle/nanorod composites prepared via low-temperature synthesis in oleic acid

Titania (TiO₂) nanorods (NRs) and nanoparticles (NPs) were synthesized using oleic acid as a surfactant and employed as photoanodes for dye sensitized solar cell (DSSC) fabrication. The synthesized NRs and NPs were characterized using transmission electron microscopy and X-ray diffraction. The photovoltaic performances were compared between NRs, NPs, and their composites. The results showed that the power conversion efficiencies (η) of the composites depend on the relative compositions of NRs and NPs in photoanodes, reaching the greatest at 10% NR content. η of the pure NRs DSSC was lower than that of the NPs DSSC. Electrochemical impedance spectroscopy revealed that the highest η at 10% NRs is mainly due to reduced charge transport resistance at the TiO₂/dye/electrolyte interface and electrolyte diffusion resistance, overcoming the reduction of the number of adsorbed dye molecules.     

Effective load transfer by a chromium carbide nanostructure in a multi-walled carbon nanotube/copper matrix composite

Multi-walled carbon nanotube (MWCNT) reinforced copper (Cu) matrix composites, which exhibit chromium (Cr) carbide nanostructures at the MWCNT/Cu interface, were prepared through a carbide formation using CuCr alloy powder. The fully densified and oriented MWCNTs dispersed throughout the composites were prepared using spark plasma sintering (SPS) followed by hot extrusion. The tensile strengths of the MWCNT/CuCr composites increased with increasing MWCNTs content, while the tensile strength of MWCNT/Cu composite decreased from that of monolithic Cu. The enhanced tensile strength of the MWCNT/CuCr composites is a result of possible load-transfer mechanisms of the interfacial Cr carbide nanostructures. The multi-wall failure of MWCNTs observed in the fracture surface of the MWCNT/CuCr composites indicates an improvement in the load-bearing capacity of the MWCNTs. This result shows that the Cr carbide nanostructures effectively transferred the tensile load to the MWCNTs during fracture through carbide nanostructure formation in the MWCNT/Cu composite.     

Reduced graphene oxide-multiwalled carbon nanotubes hybrid film with low Pt loading as counter electrode for improved photovoltaic performance of dye-sensitised solar cells

In this work, the role of reduced graphene oxide (rGO) with hyperbranched surfactant and its hybridisation with multiwalled carbon nanotubes (MWCNTs) and platinum (Pt) nanoparticles (NPs) as counter electrode (CE) were investigated to determine the photovoltaic performance of dye-sensitised solar cells (DSSCs). Sodium 1,4-bis(neopentyloxy)-3-(neopentyloxycarbonyl)-1,4-dioxobutane-2-sulphonate (TC14) surfactant was utilised as dispersing and stabilising agent in electrochemical exfoliation to synthesise graphene oxide (GO) as initial solution for rGO production prior to its further hybridisation and fabrication as thin film. A chemical reduction process utilising hydrazine hydrate was conducted to produce rGO due to the low temperature process and water-based GO solution. Subsequently, hybrid solution was prepared by mixing 1 wt% MWCNTs into the produced rGO solution. TC14-rGO and TC14-rGO_MWCNTs hybrid solution were transferred into fluorine-doped tin oxide substrate to fabricate thin film by spraying deposition method. Finally, the CE films were prepared by coating with thin Pt NPs. Photoanode film was prepared by a two-step process: hydrothermal growth method to synthesise titanium dioxide nanowires (TiO₂ NWs) and subsequent squeegee method to apply TiO₂ NPs. According to solar simulator measurement, the highest energy conversion efficiency (η) was achieved by using CE-based TC14-rGO_MWCNTs/Pt (1.553%), with the highest short current density of 4.424 mA/cm². The highest η was due to the high conductivity of CE hybrid film and the morphology of fabricated TiO₂ NWs/TiO₂ NPs. Consequently, the dye adsorption was high, and the photovoltaic performance of DSSCs was increased. This result also showed that rGO and rGO_MWCNTs hybrid can be used as considerable potential candidate materials to replace Pt gradually.     

染料敏化太阳能电池中纯铂对电极的研究进展

作为染料敏化太阳能电池的重要组成部分,对电极的催化性能和价格直接关系到电池的光电转换效率和成本。作为对电极的催化材料,导电聚合物、碳材料和无机化合物等材料虽成本低廉,但其催化性能仍不及金属铂。因此,重点综述了近年来染料敏化太阳能电池纯铂对电极的研究状况,并指出了纯铂对电极中有待解决的问题及今后的发展方向,同时还介绍了染料敏化太阳能电池的工作原理和对电极的作用。     

染料敏化太阳能电池过渡金属化合物对电极制备方法研究进展

染料敏化太阳能电池(dye-sensitized solar cells, DSSCs)作为制作工艺简易, 成本低廉, 环境友好的新型太阳能电池, 其发展一直备受关注。对电极作为DSSC的核心部件之一, 其制备工艺会直接影响到DSSC的发展和应用。以低成本高性能的催化材料代替传统的贵金属Pt对电极是降低DSSC生产成本的有效途径之一。具有类Pt催化性能的过渡金属化合物(TMCs)由于种类繁多, 制备方式简单多样, 近年来成为DSSC对电极研究中的热点。本文综述了DSSC过渡金属化合物对电极的最新研究进展, 总结概括了过渡金属化合物对电极的制备方法以及性能特点, 并对其发展方向和应用前景进行了分析。     

The formation of magnetite nanoparticles on the sidewalls of multi-walled carbon nanotubes

Linear polyethyleneimine (PEI) was used as a non-covalent functionalizing agent to modify multi-walled carbon nanotubes (MWCNTs). Fe₃O₄ nanoparticles were then formed along the sidewalls of the as-modified MWCNTs through a simple solvothermal method. X-ray diffraction, Fourier transform infrared spectrometry, transmission electron microscopy, and vibrating sample magnetometry were used to characterize the MWCNT/Fe₃O₄ nanocomposites. Results indicated that Fe₃O₄ nanoparticles with diameters ranging from 50 to 200 nm were attached to the surface of the MWCNTs by electrostatic interaction. PEI was found to improve the electrical conductivity of the MWCNT/Fe₃O₄ nanocomposites. The magnetic saturation value of these magnetic nanocomposites was 61.8 emu g⁻¹. These magnetic MWCNT/Fe₃O₄ nanocomposites are expected to have wide applications in bionanoscience and technology.     

One‐Step Hydrothermal Tailoring of NiCo2S4 Nanostructures on Conducting Oxide Substrates as an Efficient Counter Electrode in Dye‐Sensitized Solar Cells

A one‐step in situ tailoring of NiCo₂S₄ nanostructures is demonstrated on fluorine‐doped tin oxide (FTO) as Pt‐free counter electrodes (CEs) for dye‐sensitized solar cells (DSSCs) with performance surpassing that of a conventional Pt‐sputtered CE. An interconnected NiCo₂S₄ nanosheet network is successfully constructed on the FTO glass via a hydrothermal method, attributed to the synergistic effect of structure‐directing hexamethylenetetramine and L‐cysteine. A growth mechanism is proposed, and the effects of nanostructures and sulfur atomic percentages on the electrocatalytic performance are discussed in depth. A DSSC with the optimized interconnected NiCo₂S₄ nanosheet CE exhibits higher power conversion efficiency (7.22%) compared to that with a conventional Pt‐sputtered CE (6.87%) due to excellent charge transport properties and enhanced electrocatalytic activity of the NiCo₂S₄ nanostructures. This work showcases the strong potential of nanostructured ternary chalcogenides, which are composed of earth‐abundant elements and prepared through a single‐step hydrothermal process without tedious posttreatments, to reduce the dependence of platinum in DSSCs and other electrochemical devices.     

Widely dispersed PEI-based nanocomposites with multi-wall carbon nanotubes by blending with a masterbatch

High performance poly(etherimide) (PEI)-based nanocomposites (PNs) with multi-walled carbon nanotubes (MWCNT) were obtained via melt mixing. To achieve this, PEI was mixed with a well-dispersed commercial poly(butylene terephthalate) (PBT)/MWCNT master-batch in an attempt to transfer the dispersed MWCNTs to a PEI matrix. A broad and homogeneous dispersion of MWCNTs throughout the PEI-based matrix was obtained. The electrical percolation threshold (p_c) was reached at only 1 wt.% MWCNT. This p_c showed a power law dependence of conductivity on filler concentration, with a critical exponent of 1.92, which indicates that a three dimensional percolated structure was achieved. The glass transition temperature and the pressure at the output end of the extruder decreased when the master-batch was added, indicating that the processability of PEI was improved. In addition to this, the modified PEI-based PNs presented ductile behaviour and an ameliorated (12% with 5 wt.% MWCNT) elastic modulus compared with pure PEI.