Transparent Counter Electrode Research Articles

Iron-nickel-cobalt selenide nanoparticles as an efficient and transparent counter electrode for dye-sensitized solar cells

In this study, we developed a quaternary metal selenide (Fe0.35Ni0.11Co0.19Se) counter electrode (CE) material, grown onto fluorine-doped tin oxide, for dye-sensitized solar cells (DSSCs) using the potential-reversal electrochemical deposition technique at ambient conditions. Under optimized conditions, the Fe0.35Ni0.11Co0.19Se CE exhibited excellent electrocatalytic activity in the I-/I3- redox reaction with the average transmittance of 78.85 %. The additional valence states of Fe in the Ni0.3Co0.3Se electrode material further enhanced the catalytic activity during the electrochemical redox process. The DSSC employing this electrocatalytically active CE realized a power conversion efficiency of 7.73 %, surpassing the efficiency of both Pt and Ni0.3Co0.3Se CEs-based DSSCs (7.23 % and 7.23 %, respectively). This electro-preparation method offers a simpler and more cost-effective fabrication process for CE design, demonstrating a good potential for replacing expensive platinum CEs in DSSCs.

Sol–gel derived ZnO thin film as a transparent counter electrode for WO3 based electrochromic devices

Electrochromic devices (ECDs) have the ability to show color even when electrical power is disconnected. However, challenges such as simple and cost-effective electrochromic material preparation, insufficient coloration, slow switching times, and poor cycling stability have yet to be overcome. The paper describes an electrochromic device with WO3 thin film as the electrochromic material for the working electrode and ZnO thin film as a counter electrode fabricated on FTO glass substrates by a simple sol–gel spin coating method. The optical contrast at 600nm of ZnO counter electrode based ECD (12.4%) is almost double that of graphite counter electrode based ECD (6.5%), showing higher efficiency and better electrochromic response. The properties of ECD devices were also examined using cyclic voltammetry and chronoamperometry measurements with results showing that the devices were stable and the charge required to tint the device (5.6mAs) is reduced compared to typical graphite-coated counter electrode. These types of devices are promissing candidates to be used as smart windows.

Enhancing Light Harvesting in Dye-Sensitized Solar Cells through Mesoporous Silica Nanoparticle-Mediated Diffuse Scattering Back Reflectors

Dye-sensitized solar cells (DSSCs) hold unique promise in solar photovoltaics owing to their low-cost fabrication and high efficiency in ambient conditions. However, to improve their commercial viability, effective, and low-cost methods must be employed to enhance their light harvesting capabilities, and hence photovoltaic (PV) performance. Improving the absorption of incoming light is a critical strategy for maximizing solar cell efficiency while overcoming material limitations. Mesoporous silica nanoparticles (MSNs) were employed herein as a reflective layer on the back of transparent counter electrodes. Chemically synthesized MSNs were applied to DSSCs via bar coating as a facile fabrication step compatible with roll-to-roll manufacturing. The MSNs diffusely scatter the unused incident light transmitted through the DSSCs back into the photoactive layers, increasing the absorption of light by N719 dye molecules. This resulted in a 20% increase in power conversion efficiency (PCE), from 5.57% in a standard cell to 6.68% with the addition of MSNs. The improved performance is attributed to an increase in photon absorption which led to the generation of a higher number of charge carriers, thus increasing the current density in DSSCs. These results were corroborated with electrochemical impedance spectroscopy (EIS), which showed improved charge transport kinetics. The use of MSNs as reflectors proved to be an effective practical method for enhancing the performance of thin film solar cells. Due to silica’s abundance and biocompatibility, MSNs are an attractive material for meeting the low-cost and non-toxic requirements for commercially viable integrated PVs.

TiO2 Crystallization at Room Temperature and Preparation of Transparent Carbon Counter Electrode for Low-Cost Dye-Sensitized Solar Cells

TiO2 Crystallization at Room Temperature and Preparation of Transparent Carbon Counter Electrode for Low-Cost Dye-Sensitized Solar Cells

Combustion-Assisted Polyol Reduction Method to Prepare Highly Transparent and Efficient Pt Counter Electrodes for Bifacial Dye-Sensitized Solar Cells.

A combustion-assisted polyol reduction (CPR) method has been developed to deposit electrocatalytically efficient and transparent Pt counter electrodes (CEs) for bifacial dye-sensitized solar cells (DSSCs). Compared with conventional thermal decomposition of Pt precursors, CPR allows for a decrease in reduction temperature to 150 °C. The low-temperature processing is attributed to adding an organic fuel, acetylacetone (Hacac), which provides extra heat to lower reduction energy. In addition, the stable Pt complexes can simultaneously be formed in ethylene glycol (EG) and Hacac system, which leads to Pt nanoparticle size regulation. A ratio of Hacac to EG is optimized to achieve excellent electrocatalytic activity and high visible light transmittance for CEs. The bifacial DSSCs fabricated with CPR-Pt CEs (EG : Hacac=1 : 16) reach efficiencies of 6.71±0.16% and 6.41±0.15% in front and back irradiations, respectively.

Fuel-assisted polyol reduction for highly transparent and efficient Pt counter electrodes in bifacial dye-sensitized solar cells

Organic fuels allowed for manufacturing highly transparent and efficient Pt counter electrodes.

Transparent PEDOT counter electrodes for bifacial dye-sensitized solar cells using a cobalt complex mediator.

Poly(3,4-ethylenedioxythiophene) (PEDOT) aggregate-deposited counter electrodes (CEs) were applied to bifacial dye-sensitized solar cells with a cobalt complex electrolyte. The high transparency and excellent electrochemical activity of PEDOT CEs result in an impressive cell bifaciality of 0.92 under standard test conditions (AM 1.5G, 100 mW cm-2), and maximum power production of 11.3% under realistic conditions with an effective albedo of 50%.

Optically Transparent Gold Nanoparticles for DSSC Counter-Electrode: An Electrochemical Characterization.

A gold nanoparticles transparent electrode was realized by chemical reduction. This work aims to compare the transparent gold nanoparticles electrode with a more commonly utilized gold-film-coated electrode in order to investigate its potential use as counter-electrode (CE) in dye-sensitized solar cells (DSSCs). A series of DSSC devices, utilizing I−/I3− and Co(III)/(II) polypyridine redox mediators [Co(dtb)3]3+/2+; dtb = 4,4′ditert-butyl-2,2′-bipyridine)], were evaluated. The investigation focused firstly on the structural characterization of the deposited gold layers and then on the electrochemical study. The novelty of the work is the realization of a gold nanoparticles CE that reached 80% of average visible transmittance. We finally examined the performance of the transparent gold nanoparticles CE in DSSC devices. A maximum power conversion efficiency (PCE) of 4.56% was obtained with a commercial I−/I3−-based electrolyte, while a maximum 3.1% of PCE was obtained with the homemade Co-based electrolyte.

Transparent, High‐Charge Capacity Metal Mesh Electrode for Reversible Metal Electrodeposition Dynamic Windows with Dark‐State Transmission <0.1%

AbstractDynamic windows allow user control over light and heat flow to save energy and maximize comfort. Reversible metal electrodeposition (RME) dynamic windows can uniquely tint to a color‐neutral privacy state (0.1% visible light transmission). The design parameters of transparent metal mesh counter electrodes for high‐contrast RME dynamic windows: high transparency, charge capacity and surface area with low haze, sheet resistance and cost are discussed, concluding that woven metal meshes meet these design parameters. Electroplated current is measured on an indium tin oxide electrode and two meshes with different wire spacings, showing the meshes’ cylindrical geometry enable them to draw more current per square area. The mesh material composition is analyzed to ensure cycling durability in a CuBi electrolyte by developing a transparent mesh with an inert core (stainless steel, SS), a thin Au coating, and a high charge‐capacity (1.5 C cm−2) CuBi outer coating. The study demonstrates that the films maintain a consistent Cu:Bi ratio and optical properties after 250 privacy cycles or 1500 cycles to 10% transmission, showing that the Cu and Bi coating is effective in keeping the films from becoming Cu rich with cycling. Finally, a 100 cm2 device with excellent uniformity and color neutrality is demonstrated.

Tandem dye-sensitized solar cells with efficiencies surpassing 33% under dim-light conditions

To fabricate dye-sensitized solar cells (DSSCs), the variation of TiO2 film thickness elicits contrary effects on the light-harvesting and charge transfer, thereby affecting cell performance. To compromise the TiO2 thickness on the two effects, tandem DSSCs constructed by stacking two cells in series were proposed herein. Cells with high transparent photoelectrodes and counter electrodes were employed as the top cells; thus, the light unabsorbed by the top cells can be transmitted through, and harvested by the bottom cells. Furthermore, cobalt redox couple was adopted to decrease the light loss caused by absorption of the electrolyte. By regulating the film thicknesses of the top and bottom cells, both light harvest and charge transfer performance can be improved simultaneously, thereby, achieving a conversion efficiency as high as 33.98% under 2000 lx fluorescent lighting. This efficiency is much higher than the value (26.57%) obtained by the single cell. The tandem structure can also be applied under sunlight conditions, which can increase the efficiency from 9.27% to 11.31%.

Indoor Dye-Sensitized Solar Cells with Efficiencies Surpassing 26% Using Polymeric Counter Electrodes

The development of high-performance counter electrodes (CEs) for bifacial dye-sensitized solar cells (DSSCs) using nonplatinum (Pt) material is important to prepare low-cost and high-power conversion efficiency (PCE) DSSCs. In this work, poly(3,4-ethylenedioxythiophene) (PEDOT) CEs were prepared by the electrochemical deposition of PEDOT onto fluorine-doped tin oxide substrates for indoor light application. To obtain a high catalytic and high transparent CE, the thickness of the PEDOT film was controlled. Using Y123 dye and cobalt redox system, the cell performance under different light intensities (200–1000 lx) was studied. The results show that the optimal thickness of PEDOT was 90 nm, which can produce higher diffusivity, higher ionic conductivity, and lower charge transfer resistance at the CE/electrolyte interface. Accordingly, PCEs of 23.98% (200 lx), 25.83% (600 lx), and 26.93% (1000 lx) were achieved for a traditional DSSC photoelectrode containing main layer (ML) and scattering layer (SL). For bifacial cells using a newly developed sandwich photoelectrode with the ML/SL/ML structure, the front-side and rear-side efficiencies under 200 lx illumination were 24.16 and 22.45%, respectively, and the rear-to-front-side efficiency ratio was 93%. These efficiencies were much higher than those obtained using Pt CE.

Bifacial dye-sensitized solar cells utilizing green-colored NIR sensitive unsymmetrical squaraine dye

Dye-sensitized solar cells (DSSCs) with the capability of photon harvesting from both front and rear sides, consisting of newly developed NIR dye (SQ-140), iodine-based redox electrolyte, and transparent counter electrode with high bifaciality factor (BFF) and good cumulated photoconversion efficiency (PCE), are successfully fabricated and characterized. The use of transparent TiO2-based photoanode leads to improved BFF as compared to its opaque TiO2 counterparts: from 74% to 86% under similar experimental conditions and device parameters. The high molar extinction coefficient of the NIR dye SQ-140, needing a thinner TiO2 layer, was found to be advantageous to maintaining the high BFF even in thicker TiO2 films without serious compromise in the PCE. The lower efficiency of the bifacial DSSC under rear illumination was attributed to the hampered optical penetration as well as absorption of light by the intense colored iodine-based redox electrolyte.

Ultra-low-cost, flexible and durable electrochromic tape device based on aluminum foil

Electrochromic devices (ECDs) have the ability to selectively change their color state. They come in many forms, such as smart windows, e-ink displays and recently even as flexible tapes. Since most of ECDs incorporate traditional “sandwich” architecture, which requires at least one electrode to be made of a transparent conductive polymer or thin film ceramics, they are considered too expensive and fragile compared to devices made from metal or alloy foils. For the first time, we present a true low-cost, flexible and durable ECD tape that uses a common “kitchen-grade” aluminum foil for electrodes, while employing a Li-WO3 intercalation based electrochromic system. The presented ECD tape is capable of showing two color states. The tested tapes were up to 20 cm long but could be easily made longer due to their “inverted sandwich” architecture. Due to the absence of transparent counter electrode, the assembled ECD tape has excellent durability properties and could be used in color changing clothes, adaptive camouflage or other applications.

Partly Covered PProDOT‐Me2 on MoS2 Nanosheets Counter Electrode for High‐Performance Self‐Powered Electrochromic Device

AbstractDeveloping a low‐cost and transparent counter electrode (CE) for a self‐powered electrochromic device (SP‐ECD) can address the requirements of building‐integrated photovoltaics (BIPVs). Herein, a new partly covered poly(3,4‐(2,2‐dimethylpropylenedioxy) thiophene) (PProDOT‐Me2) on MoS2 nanosheets CE is developed for replacing an expensive Pt CE and achieving high‐performance SP‐ECD. The device consists of the proposed CE, an electrolyte containing Br−/Br3− redox pair, and a working electrode made with a dye‐sensitized TiO2 photoanode integrated with PProDOT‐Me2. ECD changes its color between deep blue and colorless by varying the illuminated light on and off. Measurements reveal that the ECD achieves a transmittance modulation of 46% at 580 nm with cycling stability over 500 cycles (4% contrast attenuation) that are about five times stable than that based on Pt or MoS2 CE. In addition, the switching speed between colored and bleached states is fast under a light on and off, with a coloration time of 2.1 s and a bleaching time of 1.5 s. These characteristics result from the unique design of CE and can be beneficial in accelerating the electrochromic process and enhancing the self‐powered performance for good cycling stability. This study reveals a new approach to prepare good CE for efficient SP‐ECD in BIPVs.

Portable Photovoltaic-Self-Powered Flexible Electrochromic Windows for Adaptive Envelopes

Variable transmission applications for light control or energy saving based on electrochromic materials have been successfully applied in the past in the building, sports, or automotive fields, although lower costs and ease of fabrication, installation, and maintenance are still needed for deeper market integration. In this study, all-printed large area (900 cm2 active area) flexible electrochromic devices were fabricated, and an autoregulating self-power supply was implemented through the use of organic solar cells. A new perspective was applied for automotive light transmission function, where portability and mechanical flexibility added new features for successful market implementation. Special emphasis was placed in applying solution-based scalable deposition techniques and commercially available materials (PEDOT-PSS as an electrochromic material; vanadium oxide, V2O5, as a transparent ion-storage counter electrode; and organic solar modules as the power supply). A straightforward electronic control method was designed and successfully implemented allowing for easy user control. We describe a step-by-step route following the design, materials optimization, electronic control simulation, in-solution fabrication, and scaling-up of fully functional self-powered portable electrochromic devices.

MoS2/ZIF-8 derived nitrogen doped carbon (NC)-PEDOT: PSS as optically transparent counter electrode for dye-sensitized solar cells

A few-layered MoS2 successfully grown on the nitrogen-doped carbon (NC) derived from zeolitic imidazolate framework (ZIF-8) via the hydrothermal method. A small portions of the obtained MoS2/NC composite blended with Poly (3, 4-ethylenedioxythiophene poly styrene sulfonic acid)PEDOT: PSS(as a conductive binder and utlized as counter electrode (CE) for dye-sensitized solar cells (DSSCs). The spin-coated MoS2/NC-PEDOT: PSS composite on Fluorine-doped Tin Oxide (FTO) glass not only possesses promissing catalytic ability toward the I3-/I-and [Co(bpy)3]2+/3+ redox mediators but also displayed considerable optical transparency in the visible range thus used to fabricate bi-facial DSSCs. The assembled bi-facial devices with MoS2/NC-PEDOT: PSS composite CEs showed an excellent power conversion efficiency (PCE) under both the front and the rear irradiations. The PCE of the device with 5% MoS2/NC-PEDOT: PSS composite CE and I3-/I- redox couple are 7.67 and 4.54%, under the front and rear irradiation respectively. Also, the values of the device with the same composite CE and [Co(bpy)3]2+/3+ redox mediator are 7.87 and 5.34% under the front and rear irradiation, respectively. The optimum performance of the devices with the prepared CEs and both redox systems are comparable with Pt-based devices. Thus, the MoS2/NC-PEDOT: PSS composite CEs are recommend being a promising Pt-free CEs for DSSCs.

Highly efficient and transparent counter electrode for application in bifacial solar cells

Triton X-100, DMSO and TiO2 were blended with PEDOT:PSS to produce a PEDOT:PSS/DMSO/TX100/TiO2 CE. A bifacial DSSC based on the PEDOT:PSS/DMSO/TX100/TiO2 CE was fabricated, and its photovoltaic characteristics were obtained under simulated solar light of 100 mWcm−2. Under bifacial illumination, the DSSC with the Pt CE achieved a current density (Jsc) of 16.16 mAcm−2 and system efficiency (Esys) of 8.67% while the DSSC with the PEDOT:PSS/DMSO/TX100/TiO2 CE achieved a Jsc of 17.72 mAcm−2 and a Esys of 9.14%. PEDOT:PSS/DMSO/TX100/TiO2 CE is very stable, has a high transmittance, exhibits high electro-catalytic activity, and is an excellent substitute for the Pt CE.

High stable bifacial irradiated triple-mesoporous perovskite solar cells based on AgNWs@PEDOT composite electrodes

Transparent conductive electrodes fabricated with random networks of silver nanowires (AgNWs) have been widely studied in recent years. However, the weak adhesion and chemical stability limit their further applications in perovskite solar cells. In this study, AgNWs@poly(3,4-ethylenedioxythiophene) (PEDOT)was first used as the transparent counter electrode to enhance the adhesion among AgNWs and avoid the contacts between the AgNWs and the perovskite crystals in the bifacial irradiated triple-mesoporous perovskite solar cells (PSCs). A series of XRD tests were took out and certified that the high stability of the composed films containing AgNWs@PEDOT and the perovskite crystals. A 40 days’ photocurrent-voltage test of the triple-mesoporous PSCs also proved the excellent stability and the champion power conversion efficiencies of 3.8% and 2.5% achieved from the front and the rear illumination respectively.

Preparation and Property Studies of Polyaniline Film for Flexible Counter Electrode of Dye‐Sensitized Solar Cells by Cyclic Voltammetry

AbstractIn this work, a polyaniline film was synthesized on the surface of ITO (indium tin oxide)–PET (polyethylene terephtalate) plastic substrate by cyclic voltammetry electrochemical method to prepare a transparent flexible counter electrode. Then, the surface growth mechanism of polyaniline film was analyzed, and the AC impedance and cyclic voltammetry curves were tested. The dye‐sensitized solar cell (DSSC) device was assembled for photocurrent density‐voltage curves (J‐V) test, and the photoelectric performance of the flexible polyaniline counter electrode was further discussed. All of the above tests were compared to electrochemically deposited Pt electrodes. The results show that the polyaniline has a larger specific surface area for the electrode, which is more conductive to the catalytic reduction of the iodide on the electrode. Moreover, its porous structure is more conductive to the diffusion and reaction of redox couples. Under the influence of dense layer and porous structure of polyaniline film, the cell performance of 25‐sweep‐segment polyaniline counter electrode is the best. Comparing with the conventional Pt electrode, the flexible counter electrode prepared by electrochemical synthesis not only has the same performance, but also reduces the cost by about 40 %, which is of great significance for promoting the application of DSSC.

Performance evaluation of titanium oxide deposited by electrophoresis in photoelectrodes of dye-sensitized solar cells

Nanoparticles of TiO2 have been the main semiconductor applied in Dye-sensitized solar cells (DSSCs). In this work, solar cells were developed from the electrophoretic deposition of anatase titanium dioxide (TiO2) films on conductive glasses. The electrophoretic deposition was perfomed with a constant voltage of 80V for 2 minutes and, after drying, the films were sintered at three different temperatures: 450 °C, 550 °C and 600 °C. In the assembly of the cells, the titanium dioxide films were sensitized by Ruthenizer 535-bisTBA dye (N719) and an electrolyte containing the iodide / tri-iodide redox pair and a commercial transparent platinum counter electrode were used. TiO2 films were characterized by scanning electron microscopy, dispersive energy spectroscopy and X-ray diffraction and photo-electrochemical techniques. The energy conversion rates were 0.2646% for the sintered film at 450 °C, 0.1209% for the sintered film at 550 °C and 0.1137% for the film sintered at 600 °C.