Liquid-junction Dye-sensitized Solar Cells Research Articles

Sonochemistry-assisted black/red phosphorus hybrid quantum dots for dye-sensitized solar cells

The co-sensitization of mesoscopic TiO2 anode is a promising solution to wide-spectra dye-sensitized solar cells (DSSCs) with improved power conversion efficiency. Quantum dots are featured with tunable bandgaps, small sizes and high absorption coefficients, therefore they are always combined with state-of-the-art organic dyes for co-sensitized solar cells. We present here the sonochemistry-assisted synthesis of hybrid black/red phosphorus quantum dots (BP/RPQDs) for DSSC applications. The preliminary results demonstrate that hybrid BP/RPQDs have prolonged recombination lifetime of photogenerated carriers and light-response from ultraviolet to visible and even near-infrared (NIR) region. Upon assembly into liquid-junction DSSCs, the devices with BP/RPQDs-only and BP/RPQDs-N719 co-sensitizer achieve efficiencies of 0.12% and 8.02% in comparison with 7.60% for N719-only solar cell. Using photofluorescent photoanode from mesoscopic TiO2 and long-persistence phosphor (LPP), the new-typed DSSC presents persistent power generation performances after ceasing simulated sunlight irradiation.

Ternary hybrid PtM@polyaniline (M = Ni, FeNi) counter electrodes for dye-sensitized solar cells

Developing efficient and cost-effective counter electrodes (CEs) to catalyze triiodide reduction reaction is a persistent objective for high-performance dye-sensitized solar cells (DSSCs). One promising solution is to design electron-enriched electrode materials by combining conductive polymers with alloys. In this work, ternary hybrid PtM@polyaniline (M = Ni, FeNi) CEs are synthesized by one-step replacement reaction and in-situ polymerization reaction. When assembling into liquid-junction DSSCs, the power conversion efficiencies of 8.52% and 8.39% for the devices tailored with PtNi@polyaniline and PtFeNi@polyaniline CEs can be obtained. The experimental results demonstrate that the enhanced photovoltaic performances are mainly attributed to matching work function and high electrocatalytic activity of these well-designed hybrid CEs. Arising from the competitive reactions between transition metal and I2/I3− species, the dissolution reaction of Pt in liquid electrolyte is restricted and therefore the long-term stability of corresponding devices are significantly enhanced.

Well-aligned NiPt alloy counter electrodes for high-efficiency dye-sensitized solar cell applications

Abstract Development of cost-effective and robust counter electrodes (CEs) is a persistent objective for high-efficiency dye-sensitized solar cells (DSSCs). To achieve this goal, we present here the hydrothermal synthesis of well-aligned NiPt alloy CEs, which is templated by ZnO nanowires and nanosheets. The preliminary results demonstrate that NiPt alloy electrodes are featured by increased charge-transfer processes and electrocatalytic activity in comparison with expensive Pt CE, yielding power conversion efficiencies of 8.29% and 7.41% in corresponding DSSCs with NiPt nanowire and nanosheet alloy CEs, respectively. Additionally, the NiPt alloy CEs also display extraordinary dissolution-resistant ability when suffering long-term utilization in liquid-junction DSSCs.

Alloyed PtNi counter electrodes for high-performance dye-sensitized solar cell applications

The preferred Pt counter electrode (CE) has been an economic burden for commercialization of dye-sensitized solar cells (DSSCs). To address this issue, we present here the fabrication of a series of hollow PtNi alloy CEs tailored with ZnO micro/nanostructures. The preliminary results demonstrate that alloyed PtNi electrode displays markedly increased performances in transporting charges, catalyzing redox electrolyte, and remaining persistent stability under long-term operation in comparison with standard Pt electrode. The optimized liquid-junction DSSC device from PtNi1.07 CE yields a maximal power conversion efficiency of 9.08%, suggesting a 43% enhancement compared with 6.35% for Pt based photovoltaics.

Hollow platinum alloy tailored counter electrodes for photovoltaic applications

Without sacrifice of photovoltaic performances, low-platinum alloy counter electrodes (CEs) are promising in bringing down the fabrication cost of dye-sensitized solar cells (DSSCs). We present here the realization of ZnO nanostructure assisted hollow platinum-nickel (PtNi) alloy microstructure CEs with a simple hydrothermal methods and maximization of electrocatalytic behaviors by tuning Zn precursors. The maximal power conversion efficiency is up to 8.74% for the liquid-junction dye-sensitized solar cells with alloyed PtNi0.41 electrode, yielding a 37.6% cell efficiency enhancement in comparison with pristine solar cell from planar Pt electrode. Moreover, the dissolution-resistant and charge-transfer abilities toward I−/I3− redox electrolyte have also been markedly enhanced due to competitive dissolution reactions and alloying effects.

Counter electrodes from polymorphic platinum-nickel hollow alloys for high-efficiency dye-sensitized solar cells

Precious platinum counter electrode (CE) has been an economic burden for future commercialization of dye-sensitized solar cells (DSSCs). Low-platinum alloy CE catalysts are promising in bringing down the solar cell cost without reducing photovoltaic performances. We present here a facile strategy of fabricating ZnO nanorods assisted platinum-nickel (PtNi) alloy microtube CEs for liquid-junction DSSCs. By adjusting the concentration of zinc precursors, the ZnO nanostructures and therefore PtNi alloys are optimized to maximize the electrocatalytic behaviors toward triiodide reduction reaction. The maximal power conversion efficiency is determined as high as 8.43% for liquid-junction DSSC device with alloyed PtNi microtube CE synthesized at 75 mM Zn(NO3)2 aqueous solution, yielding a 32.8% enhancement in cell efficiency in comparison with the solar cell from pristine platinum electrode. Moreover, the dissolution resistance and charge-transfer ability toward redox couples have also been markedly enhanced due to competitive dissolution reactions and alloyed effects.

Counter electrodes from conducting polymer intercalated graphene for dye-sensitized solar cells

Creation of cost-effective and platinum-free counter electrodes (CEs) is persistent for developing advanced dye-sensitized solar cells (DSSCs). We present here the fabrication of conducting polymers such as polyaniline (PANi), polypyrole (PPy), or poly(3,4-ethylenedioxythiophene) (PEDOT) intercalated reduced graphene oxide (rGO) CEs on flexible Ti foil or polyethylene-terephthalate substrate for liquid-junction DSSC applications. The ration architecture integrates the high electron-conducting ability of graphene and good electrocatalytic activity of a conducting polymer into a single CE material. The preliminary results demonstrate that the resultant CEs follow an order of rGO/PPy > rGO/PANi > rGO/PEDOT > rGO. A maximal cell efficiency of 6.23% is determined on the optimized solar cell device, yielding 104.9% enhancement in comparison to rGO based device.

ZnO nanorods assisted Ni1.1Pt and Co3.9Pt alloy microtube counter electrodes for efficient dye-sensitized solar cells

Pt counter electrode (CE) has been a burden for the commercialization of liquid-junction dye-sensitized solar cells (DSSCs). In searching for cost-effective CEs without sacrificing electrochemical activities, here we report the experimental realization of ZnO nanorods assisted Ni1.1Pt and Co3.9Pt alloy microtube (MT) CEs by combining a simple electrodeposition deposition on aligned ZnO nanorods and a galvanic displacement reaction. On behalf of the good charge-transfer ability along one-dimensional alloy electrocatalyst and electrocatalytic activity toward liquid electrolyte, the resultant DSSCs with Ni1.1Pt and Co3.9Pt MT CEs display promising power conversion efficiencies of 8.29% and 7.73%, yielding 30.6% and 21.7% enhancements, respectively. Similarly importantly, the alloyed CEs are still scalable, other alloyed low-Pt or non-Pt nano/microstructures can also be realized using the method reported here.

Counter electrodes from platinum alloy nanotube arrays with ZnO nanorod templates for dye-sensitized solar cells

Exploration of efficient platinum alloy counter electrodes (CEs) and understanding their electrocatalytic mechanism toward I3− reduction reaction have been two arising objectives for high-efficiency dye-sensitized solar cells (DSSCs). Here we demonstrate the experimental realization of bimetallic PtM (M=Pd, Ag) alloy nanotube (NT) CE electrocatalysts by an one-step templated synthesis for efficient DSSCs. The preliminary results demonstrate that the alloying of Pt with Pd or Ag for high surface-to-volume CE can significantly enhance the electrocatalytic activity in comparison with pristine Pt electrode. The promising electrocatalytic performances of the PtM CEs are mainly attributed to the good matching of their work functions to redox potential of I−/I3− couples and electron-enriched alloy surface. When fabricated into liquid-junction DSSCs, the impressive power conversion efficiencies up to 8.09% and 7.34% are determined for the cells with PtPd and PtAg NTs, yielding cell efficiencies enhancements of 18.4% and 5.9% in comparison with 6.93% for pristine Pt based DSSC, respectively. Moreover, the long-term stabilities are also increased due to competitive reactions between Pd/Ag and liquid electrolyte, protecting the Pt atoms from being dissolved by redox electrolyte.

Platinum alloy decorated polyaniline counter electrodes for dye-sensitized solar cells

In order to enhance photovoltaic performances and to reduce fabrication cost of liquid-junction dye-sensitized solar cells (DSSCs), here we report platinum alloy decorated polyaniline (PANi/MPt, M=Mo, Pd, Co) counter electrodes (CEs) by an electrochemical deposition method. In comparison with pristine PANi electrode, the integration of PANi with MPt alloys markedly enhances the electrocatalytic activity towards I3− reduction reaction. The power conversion efficiencies of 8.08%, 7.26% and 6.83% are determined from DSSCs employing PANi/CoPt, PANi/PdPt, and PANi/MoPt CEs, respectively

Cost-effective platinum alloy counter electrodes for liquid-junction dye-sensitized solar cells

One of the challenges in developing advanced dye-sensitized solar cells (DSSCs) is the pursuit of cost-effective and robust counter electrodes (CEs). We present here the successful synthesis of binary PtxM100−x (M = Ni, Co, Fe) alloy nanostructures on Ti foil by a facile and environmental-friendly strategy for utilization as CEs in liquid-junction DSSCs. Due to the reasonable charge-transfer ability and excellent electrocatalytic activity, the resultant DSSC yields a promising power conversion efficiency (PCE) of 6.42% with binary Pt0.28Ni99.72 CE in comparison with 6.18% for pristine Pt CE based device. The easy synthesis, cost-effectiveness, and good electrocatalytic property may help the Pt0.28Ni99.72 nanostructure stand out as an alternative CE electrocatalyst in a DSSC.

A branching NiCuPt alloy counter electrode for high-efficiency dye-sensitized solar cell

A rising objective for high-efficiency dye-sensitized solar cells (DSSCs) is to create extraordinary and cost-effective counter electrode (CE) electrocatalysts. We present here a branching NiCuPt alloy CE synthesized by electrodepositing Ni on ZnO microrod templates and subsequently growing branched Cu as well as suffering from a galvanic displacement for Pt uptake. The resultant NiCuPt alloy CE displays a promising electrocatalytic activity toward redox electrolyte having I−/I3− couples. An impressive power conversion efficiency of 9.66% is yielded for the liquid-junction DSSC platform.

Cobalt sulfide decorated polyaniline complex counter electrodes for efficient dye-sensitized solar cells

The practical commercialization of dye-sensitized solar cells (DSSCs) requires persistent exploration of cost-effective counter electrodes (CEs). Aiming at increasing the active sites and accelerating charge transfer of a CE electrocatalyst, cobalt sulfide decorated aniline complexes are synthesized by a reflux technique and subsequently in-situ polymerized for Pt-free polyaniline-cobalt sulfide (PANi-CoS) electrocatalysts in liquid-junction DSSCs. The preliminary results suggest that an enhanced electrocatalytic activity for I3− reduction is ascribed to the fast electron-transfer ability of PANi and the high catalytic activity of CoS. The optimized DSSC device based on PANi-7 wt% CoS yields an impressive power conversion efficiency up to 8.55% under an illumination of air mass 1.5 global simulated solar light, which is much higher than 5.65% and 5.79% for the solar cells with pure PANi and pristine Pt CEs, respectively.

Understanding the catalytic behaviour of NiM (M = Pt, Ru, Pd) counter electrode electrocatalysts in liquid-junction dye-sensitized solar cells

Understanding the electrocatalytic behaviours of counter electrode (CE) electrocatalysts favors to tune the sluggish triiodide (I3−) reduction kinetics and to compare their catalytic activities. We present here the experimental realization of cost-effective CE electrocatalysts from urchin-like NiM (M=Pt, Ru, Pd) for studying the profounding charge transfer processes without sacrificing photovoltaic performances of DSSCs. Our focus is placed on the systematic studies of catalytic activities along with modeling of I3− reduction reaction rate constant, extracting k=4πDraNB for zero-dimensional electrocatalysts. The DSSCs yield conversion efficiencies of 9.08%, 7.74%, and 6.86% with NiPt, NiRu, and NiPd CEs, respectively.

Robust counter electrodes from nanoporous NiM (M = Pt, Pd) alloys for dye-sensitized solar cells

Alloys are a class of rising counter electrode (CE) electrocatalyst candidates for dye-sensitized solar cells (DSSCs). We present here the mild solution synthesis of NiM (M=Pt, Pd) alloys using zinc oxide nanorod templates and employment as CE electrocatalysts for liquid-junction DSSC applications. Due to the good matching of work functions to redox potential of I−/I3− redox couples and reduced charge-transfer resistance at CE/electrolyte interface, the electrocatalytic activity of NiPt CE and therefore cell performances have been markedly enhanced, yielding a promising power conversion efficiency of 8.27% in the liquid-junction DSSC platform.

Optically transparent FTO-free cathode for dye-sensitized solar cells.

The woven fabric containing electrochemically platinized tungsten wire is an affordable flexible cathode for liquid-junction dye-sensitized solar cells with the I3(-)/I(-) redox mediator and electrolyte solution consisting of ionic liquids and propionitrile. The fabric-based electrode outperforms the thermally platinized FTO in serial ohmic resistance and charge-transfer resistance for triiodide reduction, and it offers comparable or better optical transparency in the visible and particularly in the near-IR spectral region. The electrode exhibits good stability during electrochemical loading and storage at open circuit. The dye-sensitized solar cells with a C101-sensitized titania photoanode and either Pt-W/PEN or Pt-FTO cathodes show a comparable performance.

A novel quasi-solid state dye-sensitized solar cell fabricated using a multifunctional network polymer membrane electrolyte

A series of liquid junction dye-sensitized solar cells (DSCs) was fabricated based on polymer membrane-encapsulated dye-sensitized TiO2 nanoparticles, prepared using a surface-induced cross-linking polymerization reaction, to investigate the dependence of the solar cell performance on the encapsulating membrane layer thickness. The ion conductivity decreased as the membrane thickness increased; however, the long term-stability of the devices improved with increasing membrane thickness. Nanoparticles encapsulated in a thick membrane (ca. 37 nm), obtained using a 90 min polymerization time, exhibited excellent pore filling among TiO2 particles. This nanoparticle layer was used to fabricate a thin-layered, quasi-solid state DSC. The thick membrane prevented short-circuit paths from forming between the counter and the TiO2 electrode, thereby reducing the minimum necessary electrode separation distance. The quasi-solid state DSC yielded a high power conversion efficiency (7.6 → 8.1%) and excellent stability during heating at 65 °C over 30 days. These performance characteristics were superior to those obtained from a conventional DSC (7.5 → 3.5%) prepared using a TiO2 active layer with the same thickness. The reduced electrode separation distance shortened the charge transport pathways, which compensated for the reduced ion conductivity in the polymer gel electrolyte. Excellent pore filling on the TiO2 particles minimized the exposure of the dye to the liquid and reduced dye detachment.

Self-Organized One-DimensionalTiO2Nanotube/Nanowire Array Films for Use in Excitonic Solar Cells: A Review

We review the use of self-assembled, vertically oriented one-dimensional (1D) titania nanowire and nanotube geometries in several third-generation excitonic solar cell designs including those based upon bulk heterojunction, ordered heterojunction, Förster resonance energy transfer (FRET), and liquid-junction dye-sensitized solar cells (DSSCs).