Sodium carboxymethyl starch-based highly conductive gel electrolyte for quasi-solid-state quantum dot-sensitized solar cells

Research on Chemical Intermediates - Liquid-junction quantum dot sensitized solar cells (QDSCs) have been facing a long stability issue due to the volatilization and leakage of liquid electrolytes....     

Highly efficient CdS quantum dot-sensitized solar cells based on a modified polysulfide electrolyte

A modified polysulfide redox couple, [(CH(3))(4)N](2)S/[(CH(3))(4)N](2)S(n), in an organic solvent (3-methoxypropionitrile) was employed in CdS quantum dot (QD)-sensitized solar cells (QDSSCs), and an unprecedented energy conversion efficiency of up to 3.2% was obtained under AM 1.5 G illumination. The QDs were linked to nanoporous TiO(2) via covalent bonds by using thioglycolic acid, and chemical bath deposition in an organic solvent was then used to prepare the QDSSCs, facilitating high wettability and superior penetration capability of the TiO(2) films. A very high fill factor of 0.89 was observed with the optimized QDSSCs.     

Ag2S quantum dot-sensitized solar cells

We present a new photosensitizer – Ag₂S quantum dots (QDs) – for solar cells. The QDs were grown by the successive ionic layer adsorption and reaction deposition method. The assembled Ag₂S-QD solar cells yield a best power conversion efficiency of 1.70% and a short-circuit current of 1.54 mA/cm² under 10.8% sun. The solar cells have a maximal external quantum efficiency (EQE) of 50% at λ = 530 nm and an average EQE of ～ 42% over the spectral range of 400–1000 nm. The effective photovoltaic range covers the visible and near-infrared spectral regions and is ～ 2–4 times broader than that of the cadmium chalcogenide systems — CdS and CdSe. The results show that Ag₂S QDs can be used as a highly efficient and broadband sensitizer for solar cells.     

A flexible photoelectrode for CdS/CdSe quantum dot-sensitized solar cells (QDSSCs)

We, for the first time, prepared a flexible photoelectrode for CdS/CdSe quantum dot-sensitized solar cells (QDSSCs). A power conversion efficiency of 3.47% was achieved under AM 1.5G illumination for a sandwich type QDSSC consisting of this flexible photoelectrode, Cu(2)S counter electrode and polysulfide electrolyte between the electrodes.     

A polymer electrolyte containing ionic liquid for possible applications in photoelectrochemical solar cells

Various iodide ion conducting polymer electrolytes have been studied as candidate materials for fabricating photoelectrochemical (PEC) solar cells and energy storage devices. In this study, enhanced ionic conductivity values were obtained for the ionic liquid tetrahexylammonium iodide containing polyethylene oxide (PEO)-based plasticized electrolytes. The analysis of thermal properties revealed the existence of two phases in the electrolyte, and the conductivity measurements showed a marked conductivity enhancement during the melting of the plasticizer-rich phase of the electrolyte. Annealed electrolyte samples showed better conductivity than nonannealed samples, revealing the existence of hysteresis. The optimum conductivity was shown for the electrolytes with PEO:salt = 100:15 mass ratio, and this sample exhibited the minimum glass transition temperature of 72.2 °C. For this optimum PEO to salt ratio, the conductivity of nonannealed electrolyte was 4.4 × 10⁻⁴ S cm⁻¹ and that of the annealed sample was 4.6 × 10⁻⁴ S cm⁻¹ at 30 °C. An all solid PEC solar cell was fabricated using this annealed electrolyte. The short circuit current density (I _SC), the open circuit voltage (V _OC), and the power conversion efficiency of the cell are 0.63 mA cm⁻², 0.76 V, and 0.47% under the irradiation of 600 W m⁻² light.     

A novel deep eutectic solvent-based ionic liquid used as electrolyte for dye-sensitized solar cells

We utilize a quaternary ammonium salt-derivative ionic liquid called G.CI which is a eutectic mixture of glycerol and choline iodide as electrolyte for dye-sensitized solar cells. Such eutectic compound belongs to a new series of ionic liquid called deep eutectic solvents (DES), which possess many outstanding features compared to the traditional imidazolium-based ionic liquids including cheap raw materials, simple preparation procedures and better biocompatibility. Current–voltage characteristics of the G.CI/PMII-based binary electrolytes stand at 0.533 V on V_oc, 12.0 mA cm^?2 on J_sc, 0.582 on fill factor, and 3.88% cell efficiency under AM 1.5, 100 mW/cm² illuminations. The comparable cell performance together with all the above advantages makes G.CI as a strong candidate for future electrolyte development for dye-sensitized solar cells (DSSCs).     

A thiolate/disulfide ionic liquid electrolyte for organic dye-sensitized solar cells based on Pt-free counter electrodes

The ionic liquid, 1-ethyl-3-methylimidazolium tetracyanoborate, was employed to prepare a thiolate/disulfide ionic liquid electrolyte with low viscosity for organic dye-sensitized solar cells (DSCs). CoS was introduced and showed better photovoltaic performance in DSCs than the ubiquitous platinized FTO CE.     

A supercooled imidazolium iodide ionic liquid as a low-viscosity electrolyte for dye-sensitized solar cells

A series of allyl-functionalized imidazolium salts are reported, including 1-allyl-3-ethylimidazolium iodide and 1-allyl-3-propylimidazolium iodide, which have melting points close to room temperature and show typical properties of supercooled fluids if heated above their melting points. Their viscosities in the liquid state are considerably lower than the benchmark ionic liquid used in solar cells, viz., 1-propyl-3-methylimidazolium iodide. Electrolytes containing these new liquids provide excellent efficiencies and good stability in dye-sensitized solar cells when subjected to an accelerated-light soaking test at 60 degrees C. The structures of three of the new salts have been established in the solid state by single-crystal X-ray analysis.     

Double-layer TiO2 inverse opal-based quantum dot-sensitized solar cells

Journal of Solid State Electrochemistry - The operation of dye-sensitized solar cells and quantum dot-sensitized solar cells (QDSSCs) depends strongly on the photoanode material employed. This is...     

Stable mesoscopic dye-sensitized solar cells based on tetracyanoborate ionic liquid electrolyte

A stable dye-sensitized solar cell has been obtained based on a new binary ionic liquid electrolyte system containing 1-propyl-3-methylimidazolium iodide and 1-ethyl-3-methylimidazolium tetracyanoborate.     

Ag2S quantum dot-sensitized WO3 photoelectrodes for solar cells

This work investigates the photovoltaic properties of new-architecture Ag₂S quantum dot-sensitized solar cells (QDSCs) fabricated on WO₃ electrodes. Liquid-junction Ag₂S QDSCs were fabricated from QDs synthesized using the successive ionic layer adsorption and reaction process. The optimal QDSC yielded an efficiency η of 0.20 % under a 100-mW/cm² light illumination. Coating the QDSC with a compact layer and a scattering layer improved η to 0.31 % with a short-circuit current density J _sc of 5.81 mA/cm² and an open-circuit voltage V _oc of 0.21 V. η increased to 0.53 % at a reduced 0.1 sun illumination with a J _sc of 1.11 mA/cm². The external quantum efficiency (EQE) spectrum covered the spectral range of 350–900 nm with a maximal EQE of 29 % at λ?=?650 nm. This work demonstrates the feasibility of the new-configuration Ag₂S QDSCs fabricated on WO₃ electrodes.     

An iodine-free electrolyte based on ionic liquid polymers for all-solid-state dye-sensitized solar cells

An ionic liquid polymer, poly (1-alkyl-3-(acryloyloxy)hexylimidazolium iodide), was employed as an iodine-free electrolyte in all-solid-state dye-sensitized solar cells with an overall conversion efficiency of 5.29% under AM 1.5 simulated solar light (100 mW cm(-2)) illumination.     

Synthesis of Mn-doped zinc blende CdSe nanocrystals for quantum dot-sensitized solar cells

Mn-doped CdSe quantum dots (QDs) with a zinc blende structure were synthesized via a phosphine-free method in octadecene (ODE) and oleic acid. The structure, size, morphology, and optical property of the QDs were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and UV–visible absorption spectra (UV–Vis), respectively. The QDs were assembled onto a microporous TiO₂ photoanode by an ex situ ligand exchange route. Quantum dot-sensitized solar cells (QDSCs) based on the above-synthesized QDs and polysulfide electrolytes were fabricated. The photovoltaic performance and impedance of the CdSe and Mn-doped CdSe QDSCs were further investigated. An improvement in efficiency to 1.84 % was achieved as compared with 0.94 % for the QDSCs based on the pure CdSe QDs. The improvement was ascribed to the existence of long-lived high-energy doping levels on the large-sized Mn-doped CdSe QDs, which provides a significant driving force for faster charge separation and electron transfer.     

Efficiency enhancement in PbS/CdS quantum dot-sensitized solar cells by plasmonic Ag nanoparticles

Journal of Solid State Electrochemistry - Semiconductor quantum dots (Q-dots) are attractive nanomaterials to be used in numerous research areas and device fabrication such as sensors,...     

High efficiency dye-sensitized nanocrystalline solar cells based on ionic liquid polymer gel electrolyte

An ionic liquid polymer gel containing 1-methyl-3-propylimidazolium iodide (MPII) and poly(vinylidenefluoride-co-hexafluoropropylene) (PVDF-HFP) has been employed as quasi-solid-state electrolyte in dye-sensitized nanocrystalline TiO2 solar cells with an overall conversion efficiency of 5.3% at AM 1.5 illumination.     

High-efficiency cascade CdS/CdSe quantum dot-sensitized solar cells based on hierarchical tetrapod-like ZnO nanoparticles

Quantum dot-sensitized solar cells (QDSCs) constructed using cascade CdS/CdSe sensitizers and the novel tetrapod-like ZnO nanoparticles have been fabricated. The cascade co-sensitized QDSCs manifested good electron transfer dynamics and overall power conversion efficiency, compared to single CdS- or CdSe-sensitized cells. The preliminary CdS layer is not only energetically favorable to electron transfer but behaves as a passivation layer to diminish the formation of interfacial defects during CdSe synthesis. On the other hand, the anisotropic tetrapod-like ZnO nanoparticles, with a high electron diffusion coefficient, can afford a better carrier transport than traditional ZnO nanoparticles. The resultant solar cell yielded an excellent performance with a solar power conversion efficiency of 4.24% under simulated one sun (AM1.5G, 100 mW cm(-2)) illumination.     

PbS quantum dot sensitized anatase TiO2 nanocorals for quantum dot-sensitized solar cell applications

Lead sulphide (PbS) quantum dot (QD) sensitized anatase TiO(2) nanocorals (TNC) were synthesized by SILAR and hydrothermal techniques. The TNC, PbS and PbS-TNC samples were characterized by optical absorption, XRD, FT-IR, FESEM and XPS. The results show that PbS QDs are coated on the TNCs, the optical absorption is found to be enhanced and the band edge is shifted to ~693 nm as compared with plain TNCs at 340 nm. The PbS-TNC sample exhibits an improved photoelectrochemical performance with a maximum short circuit current (J(sc)) of 3.84 mA cm(-2). The photocurrent density was found to be enhanced 2 fold, as compared with those of the bare PbS photoelectrode. The total power conversion efficiency of the PbS-TNC electrodes is 1.23%.     

A solvent-free, SeCN-/(SeCN)3- based ionic liquid electrolyte for high-efficiency dye-sensitized nanocrystalline solar cells

A solvent-free ionic liquid electrolyte based on the SeCN-/(SeCN)3- redox couple has been employed for high-efficiency dye-sensitized nanocrystalline solar cells. For the first time an alternative redox couple has been identified to rival and even exceed the performance of the iodide/triiodide couple even at full sunlight. Unprecedented 7.5-8.3% power conversion efficiencies under AM 1.5 sunlight have been achieved for photovoltaic devices with solvent-free ionic liquid electrolytes.     

Quantum dot-sensitized solar cells incorporating nanomaterials

Quantum dot-sensitized solar cells (QDSSCs) are interesting energy devices because of their (i) impressive ability to harvest sunlight and generate multiple electron/hole pairs, (ii) ease of fabrication, and (iii) low cost. The power conversion efficiencies (η) of most QDSSCs (typically <4%) are, however, less than those (up to 12%) of dye-sensitized solar cells, mainly because of narrow absorption ranges and charge recombination occurring at the QD-electrolyte and TiO(2)-electrolyte interfaces. To further increase the values of η of QDSSCs, it will be necessary to develop new types of working electrodes, sensitizers, counter electrodes and electrolytes. This Feature Article describes the nanomaterials that have been used recently as electronic conductors, sensitizers and counter electrodes in QDSSCs. The nature, size, morphology and quantity of these nanomaterials all play important roles affecting the efficiencies of electron injection and light harvesting. We discuss the behavior of several important types of semiconductor nanomaterials (sensitizers, including CdS, Ag(2)S, CdSe, CdTe, CdHgTe, InAs and PbS) and nanomaterials (notably TiO(2), ZnO and carbon-based species) that have been developed to improve the electron transport efficiency of QDSSCs. We point out the preparation of new generations of nanomaterials for QDSSCs and the types of electrolytes, particularly iodide/triiodide electrolytes (I(-)/I(3)(-)), polysulfide electrolytes (S(2-)/S(x)(2-)), and cobalt redox couples ([Co(o-phen)(3)(2+)/(3+)]), that improve their lifetimes. With advances in nanotechnology, we foresee significant improvements in the efficiency (η > 6%) and durability (>3000 h) of QDSSCs.