Electrochemically polymerized poly (3, 4-phenylenedioxythiophene) as efficient and transparent counter electrode for dye sensitized solar cells

Influence of Nitrogen and Sulfur Doping of Carbon Xerogels on the Performance and Stability of Counter Electrodes in Dye Sensitized Solar Cells

In this work, carbon xerogels (CXGs) doped with nitrogen or sulfur have been investigated as DSSC counter electrodes. CXGs have been prepared by a sol–gel method from resorcinol and formaldehyde and subsequent carbonization. Nitrogen doping has been carried out by introducing melamine into the synthesis process along with resorcinol and formaldehyde, while sulfur has been incorporated by direct reaction of the carbon material with elemental sulfur. The counter electrodes for DSSCs have been prepared by airbrushing on conductive glass (fluorine-doped tin oxide, FTO), and their electrochemical behavior has been evaluated, observing that the introduction of heteroatoms such as nitrogen or sulfur leads to an improvement in efficiency compared to the undoped material thanks to a decrease in charge transfer resistance.

Interfacial Assembly and Applications of Functional Mesoporous Materials

Functional mesoporous materials have gained tremendous attention due to their distinctive properties and potential applications. In recent decades, the self-assembly of micelles and framework precursors into mesostructures on the liquid-solid, liquid-liquid, and gas-liquid interface has been explored in the construction of functional mesoporous materials with diverse compositions, morphologies, mesostructures, and pore sizes. Compared with the one-phase solution synthetic approach, the introduction of a two-phase interface in the synthetic system changes self-assembly behaviors between micelles and framework species, leading to the possibility for the on-demand fabrication of unique mesoporous architectures. In addition, controlling the interfacial tension is critical to manipulate the self-assembly process for precise synthesis. In particular, recent breakthroughs based on the concept of the "monomicelles" assembly mechanism are very promising and interesting for the synthesis of functional mesoporous materials with the precise control. In this review, we highlight the synthetic strategies, principles, and interface engineering at the macroscale, microscale, and nanoscale for oriented interfacial assembly of functional mesoporous materials over the past 10 years. The potential applications in various fields, including adsorption, separation, sensors, catalysis, energy storage, solar cells, and biomedicine, are discussed. Finally, we also propose the remaining challenges, possible directions, and opportunities in this field for the future outlook.

Electrochemical Biosensors Based on Conducting Polymers: A Review

Conducting polymers are an important class of functional materials that has been widely applied to fabricate electrochemical biosensors, because of their interesting and tunable chemical, electrical, and structural properties. Conducting polymers can also be designed through chemical grafting of functional groups, nanostructured, or associated with other functional materials such as nanoparticles to provide tremendous improvements in sensitivity, selectivity, stability and reproducibility of the biosensor’s response to a variety of bioanalytes. Such biosensors are expected to play a growing and significant role in delivering the diagnostic information and therapy monitoring since they have advantages including their low cost and low detection limit. Therefore, this article starts with the description of electroanalytical methods (potentiometry, amperometry, conductometry, voltammetry, impedometry) used in electrochemical biosensors, and continues with a review of the recent advances in the application of conducting polymers in the recognition of bioanalytes leading to the development of enzyme based biosensors, immunosensors, DNA biosensors, and whole-cell biosensors.

In situ preparation of Ru-N-doped template-free mesoporous carbons as a transparent counter electrode for bifacial dye-sensitized solar cells

The development of a highly active, long-lasting, and cost-effective electrocatalyst as an alternative to platinum (Pt) is a vital issue for the commercialization of dye-sensitized solar cells. In this study, Ru-N-doped template-free mesoporous carbon (Ru-N-TMC) was prepared by the direct stabilization and carbonization of the poly(butyl acrylate)-b-polyacrylonitrile (PBA-b-PAN) block copolymer and ruthenium(iii) acetylacetonate [Ru(acac)3]. During the stabilization process, microphase separation occurred in the PBA-b-PAN block copolymer due to the incompatibility between the two blocks, and the PAN block transformed to N-doped semi-graphitic carbon. In the carbonization step, the PBA block was eliminated as a porous template, creating hierarchal mesopores/micropores. Meanwhile, Ru(acac)3 was decomposed to Ru, which was homogeneously distributed over the carbon substrate and anchored through N and O heteroatoms. The resulting Ru-N-TMC showed ultra-low charge transfer resistance (Rct = 0.034 Ω cm2) in the Co(bipyridine)33+/2+ reduction reaction, indicating very high electrocatalytic ability. Even though it is a transparent counter electrode (CE, average visible transmittance of 42.25%), covering a small fraction of the fluorine doped tin oxide (FTO)/glass substrate with Ru-N-TMC, it led to lower charge transfer resistance (Rct = 0.55 Ω cm2) compared to Pt (Rct = 1.00 Ω cm2). The Ru-N-TMC counter electrode exhibited a superior power conversion efficiency (PCE) of 11.42% compared to Pt (11.16%) when employed in SGT-021/Co(bpy)33+/2+ based dye-sensitized solar cells (DSSCs). Furthermore, a remarkable PCE of 10.13% and 8.64% from front and rear illumination, respectively, was obtained when the Ru-N-TMC counter electrode was employed in a bifacial DSSC. The outstanding catalytic activity and PCE of Ru-N-TMC were due to the high surface area of Ru-N-TMC, which contained numerous active species (Ru and N), easily facilitated to redox ions through the hierarchical microporous/mesoporous structure.

Recent advances in poly(3,4-ethylenedioxyselenophene) and related polymers

This review highlights the recent progress in synthesis, properties, applications and future outlook of PEDOS based conjugated polymers.

There Is a Future for N-Heterocyclic Carbene Iron(II) Dyes in Dye-Sensitized Solar Cells: Improving Performance through Changes in the Electrolyte

By systematic tuning of the components of the electrolyte, the performances of dye-sensitized solar cells (DSCs) with an N-heterocyclic carbene iron(II) dye have been significantly improved. The beneficial effects of an increased Li+ ion concentration in the electrolyte lead to photoconversion efficiencies (PCEs) up to 0.66% for fully masked cells (representing 11.8% relative to 100% set for N719) and an external quantum efficiency maximum (EQEmax) up to approximately 25% due to an increased short-circuit current density (JSC). A study of the effects of varying the length of the alkyl chain in 1-alkyl-3-methylimidazolium iodide ionic liquids (ILs) shows that a longer chain results in an increase in JSC with an overall efficiency up to 0.61% (10.9% relative to N719 set at 100%) on going from n-methyl to n-butyl chain, although an n-hexyl chain leads to no further gain in PCE. The results of electrochemical impedance spectroscopy (EIS) support the trends in JSC and open-circuit voltage (VOC) parameters. A change in the counterion from I- to [BF4]- for 1-propyl-3-methylimidazolium iodide ionic liquid leads to DSCs with a remarkably high JSC value for an N-heterocyclic carbene iron(II) dye of 4.90 mA cm-2, but a low VOC of 244 mV. Our investigations have shown that an increased concentration of Li+ in combination with an optimized alkyl chain length in the 1-alkyl-3-methylimidazolium iodide IL in the electrolyte leads to iron(II)-sensitized DSC performances comparable with those of containing some copper(I)-based dyes.

A study of the influence of plasmonic resonance of gold nanoparticle doped PEDOT: PSS on the performance of organic solar cells based on CuPc/C60

This work studied the role of gold nanoparticles (AuNPs) with different spherical sizes mixed with poly (3, 4-ethylene dioxythiophene): polystyrene sulfonate (PEDOT: PSS) as a hole transfer layer to enhance the efficiency (ITO/PEDOT:PSS (AuNPs)/CuPc/C₆₀/Al) organic photovoltaic cell (OPV). AuNPs were synthesized using the thermochemical method and the results of the transmission electron microscope (TEM) images showed that the gold nanoparticles mostly dominated by spherical shapes and sizes were calculated in the range (12–23 nm). Measurements of UV-VIS spectra for AuNPs have shown that the surface plasmon resonance shifted to a higher wavelength with decreasing the particle size. Surface morphology and absorption spectra of OPV cells were studied using atomic force microscope and UV-VIS spectrometer techniques. The efficiency of the OPV cell was calculated without and with AuNPs. Efficiency was increased from 0.78% to 1.02% due to the embedded of AuNPs with (12 nm) in PEDOT/PSS. The increase in the light absorption in CuPc is due to the good transparent conducting of PEDOT:PSS and the increase in the electric field around AuNPs embedded in PEDOT:PSS and inbuilt electric field at the interfacial between CuPc and C₆₀ is due to the surface plasmon resonance of AuNPs. The increase in these two factors increase the exciton generation in CuPc, dissociation at the interfacial layer, and charge carrier transfer which increases the collection of electrons and holes at cathode and anode.

Photovoltaic Characteristics of Multiwalled Carbon Nanotube Counter-Electrode Materials for Dye-Sensitized Solar Cells Produced by Chemical Treatment and Addition of Dispersant

Multiwalled carbon nanotubes (MWCNTs) have excellent electrical conductivity and good chemical stability, and are used as counter electrodes in dye-sensitized solar cells (DSSCs). The counter electrodes collect electrons from the external circuit and catalyze the redox reaction in the electrolyte. Electrocatalysis is an important step for generating energy from triiodide reduction in DSSCs. In this study, chemically treated MWCNTs were investigated for improving the photovoltaic performance of DSSCs. The MWCNTs were modified through chemical oxidation with sulfuric acid/nitric acid (H2SO4/HNO3) or potassium persulfate/sodium hydroxide (K2S2O8/NaOH). Nanocellulose (CNC) was used as a dispersant to improve the photovoltaic performance and dispersibility as an alternative material for counter electrodes in DSSCs. The counter electrodes were prepared on fluorine-doped tin oxide (FTO) glass substrates by spin coating nanofluids. Morphological and structural investigations were performed using scanning transmission electron microscopy (TEM), Fourier-transform infrared (FTIR) spectroscopy, and Raman spectroscopy. The electrical conductivity and UV light absorption of the DSSCs were analyzed to evaluate their photovoltaic performance. The results of these analyses showed that chemical functionalization and addition of CNC were effective for increasing the electrical conductivity and UV light absorption. Finally, all result trends were the same. Increasing the dispersibility of the counter electrode was found to improve the reduction of I3− at the interface between the MWCNTs and the electrolyte, thereby, improving the energy conversion efficiency.