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High-quality perovskite film is deposited on a 30 cm × 40 cm LiCoO2-coated ITO/glass via newly developed freely falling anti-solvent extraction (FFASE) method followed by post watervapor annealing in an ambient atmosphere. Perovskite solar modules (PSMs, active area of 25.2 cm2 with mask) based on this high-quality film achieve the highest efficiency of 16.04 and 30.76% under 1 sun (100 mW cm-2) and 945 lux fluorescent light illumination, respectively. The encapsulated PSMs are stable at -20 to 80 °C thermal cycling and keep high efficiency at temperature as low as -20 °C and as high as 80 °C. When the encapsulated PSM is heated at 85 °C and 85% relative humidity under room lighting or heated at 60 °C under AM1.5 (100 mW cm-2) illumination for 1000 h, loses only "8% of its original efficiency. The high stability of PSMs is due to very high quality perovskite absorber being used. The underlying concept of the FFASE method for extracting the solvent from the large-area perovskite precursor film is that the whole precursor film contacts with the fresh anti-solvent during the crystallization stage. [ABSTRACT FROM AUTHOR]

The dye regeneration step in a dye‐sensitized solar cell (DSSC) affects significantly the device efficiency. To be able to predict the dye regeneration efficiency by the electrolyte this paper provides a facile way to design high‐efficiency sensitizers for DSSC. This paper proposes, for the first time, a simple and ingenious way to identify the dye regeneration sites and their relative efficiencies when a specific electrolyte is used. Two steps are proposed to identify the dye regeneration sites and their relative regeneration efficiencies: (1) drawing all the resonance structures of the oxidized dye to determine the regeneration sites, and (2) choosing the most favored site for dye regeneration as the chemically softest (when the redox couple used is soft I−/I3− pair) and the least spatially hindered site. The regeneration sites identified by the resonance structures are consistent with the β‐LUSO (β lowest unoccupied spin orbital) distribution, which is generally used for identifying the dye regeneration sites, calculated with DT‐DFT theory. The relative dye regeneration efficiency and photovoltaic performance of both ruthenium and metal‐free organic dyes predicted by the method reported here are supported by experimental data and the proposed dye regeneration mechanism. Several types of dye molecules are used to demonstrate the correctness of this new tool. This non‐classical tool, which uses the well‐known chemical knowledge of the resonance structure and hard–soft acid–base principle, without any computer calculation or physicochemical measurement, provides a very simple and powerful tool to quickly conceive high‐efficiency sensitizers for DSSCs. [ABSTRACT FROM AUTHOR]

Low‐temperature sol‐gel prepared ZnCo2O4 spinel‐based thin films are developed as high‐performance hole transporting layer (HTL) for coating perovskite film (NA‐Psk) from the basic MAPbI3/ACN/CH3NH2 solution in air without using anti‐solvent. Inverted PSC based on 2 mole% (vs Zn) Cu2+ doped ZnCo2O4 (2%Cu@ZnCo2O4) HTL and NA‐Psk absorber exhibit the maximum power conversion efficiency (PCE) of 20.0% with no current hysteresis while the cell based on ZnCo2O4 and PEDOT:PSS HTL (using NA‐Psk absorber) achieves the PCE of 15.79% and 12.3% with a current hysteresis index of 9.8% and 32.4%, respectively. Without encapsulation, PSCs based on 2%Cu@ZnCo2O4, ZnCo2O4, and PEDOT:PSS HTLs maintain 90%, 77%, and 12%, respectively of the original efficiency by standing in ambient atmosphere (temperature: 20–25 °C, RH:30%–40%) for 1800 h. Large area (10 cm × 10 cm substrate) perovskite mini‐module (PSM) with PCE over 15% is also demonstrated by using sol‐gel prepared 2%Cu@ZnCo2O4 HTL. The poor photovoltaic performance of PEDOT:PSS HTL is due to the basic MAPbI3/ACN/CH3NH2 solution will deprotonate the acidic PEDOT:PSS to reduce its conductivity whereas ZnCo2O4 HTL are not affected by basic perovskite precursor solution. [ABSTRACT FROM AUTHOR]

Abstract: Four donor–conjugated spacer–acceptor (D–π–A) organic dyes containing cyclopentadithiophene unit as a part of the conjugated spacer are prepared and studied to investigate the effects of the conjugated spacer and donor on the short-circuit current and conversion efficiency of the corresponding DSSCs. Theoretical calculations reveal that a shorter conjugated spacer or a stronger donor leads to more effective electron injection upon photo excitation. Therefore, D–π–A typed dye with longer conjugated spacer may have higher absorption coefficient and longer λ max. Nevertheless, it may also have lower effective electron injection upon photo excitation. Calculation data also show that cyclopentadithiophene although is a good moiety for extending the conjugation length of the organic dyes, it also acts as an electron sink, decreasing the effective electron injection. The transition probability calculated with the electron density difference analyses combining with the experimental absorption and photovoltaic performance data provides a useful protocol for designing organic photosensitizers for DSSCs at the electronic and structural levels. [Copyright &y& Elsevier]

Highlights: [•] Highly conducting and good thermal stability M-PEDOT:PSS films are prepared from PEDOT:PSS/H2O/EG/HFIP solution. [•] The conductivity of M-PEDOT:PSS is higher enough to replace FTO as a counter electrode in DSC. [•] Pt-free DSC device based on PEDOT/M-PEDOT:PSS counter electrode, N719 sensitizer, and liquid electrolyte achieves the conversion efficiency of 7.29%. [ABSTRACT FROM AUTHOR]

Seven new donor-spacer-acceptor metal-free organic dyes containing a fluorene and/or thiophene unit as a conjugated spacer are prepared and their physicochemical properties as well as photovoltaic performance are studied. The electron transfer from donor to acceptor upon excitation of these dyes is sensitive to the conjugated spacers. If a stronger donor moiety such as (ethylenedioxy)thiophene is used as a spacer, such as in F-E1 dye, the dye molecule has a better charge separation and therefore high efficiency. Furthermore, for the same donor and acceptor, fluorene is a better conjugated spacer than the bithiophene moiety because of its nonplanar conformation, which avoids the electron-hole recombination of dye upon photoexcitation. Short molecules with planar conformation aggregate easily, and the corresponding device reveals low open-circuit voltage Voc. On the other hand, dye molecules with long alkyl side chains (large size) adsorb less on the TiO2 electrode, which results in a smaller short-circuit current density Jsc. The difference in the efficiency of these dyes is small except for F-1 (owing to its short conjugation length), and electron density difference map analyses reveal that photoexcitation transfer of electron density from the donating moieties toward the acceptor/anchoring units occurs for all molecules. The small difference in the efficiency is attributed partly to the degree of effective charge transfer upon excitation, not totally to the absorption profile of the dye molecules. Furthermore, time-dependent DFT simulated absorption spectra are in excellent agreement with experimental spectra when the dyes are in their protonated states in THF solution. The transition probability calculated with the electron density difference analyses combined with the absorption data and photovoltaic performance provide useful information for designing organic sensitizers for dye-sensitized solar cells. [ABSTRACT FROM AUTHOR]

Abstract: A series of conjugated/non-conjugated copolymers and their corresponding oligomers were prepared and their optical and physical properties were investigated for understanding the merit of blocking the conjugated chromophores with non-conjugated spacers. It was found that compared to the oligomers, copolymers have the advantages of amorphous nature, high thermal stability, and good thin film processability without sacrificing the quantum efficiency and purity of the emission color. Furthermore, based on the optical data of these copolymers and oligomers, the conjugation length of the polyoctylthiophene was estimated to be extended over 23–31 octylthiophene rings. [Copyright &y& Elsevier]

Abstract: Highly conducting porous polymer electrolytes comprised of poly(vinylidene-fluoride-co-hexafluoropropylene) (PVdF-HFP), metal oxide (TiO2, MgO, ZnO)/or mesoporous zeolite (MCM-41, SBA-15), ethylene carbonate (EC), propylene carbonate (PC), and LiClO4 were fabricated with a simple direct evaporation method. It was found that when metal oxide or mesoporous zeolite was mixed with PVdF-HFP, the impedance spectroscopy showed that the room temperature conductivity increased from 1.2×10−3 Scm−1 (for pure PVdF-HFP) to 2.1×10−3 Scm−1. SEM micrographs showed that the pore size of the composite membrane was similar to that of pure PVdF-HFP membrane but the porosity decreased, nevertheless the solution uptake increased. The increasing in solution uptake is not related directly to the surface area or dielectric constant of the oxides. It may be due to the affinity of the metal oxide toward the electrolyte solution. Furthermore, the solution leakage of PVdF-HFP/MgO and PVdF-HFP/SBA-15 composite electrolytes also decreased compared to pure PVdF-HFP electrolyte. These polymer composite electrolytes were stable up to 5.5V (versus Li/Li+) and the lithium ion cells assembled with these polymer electrolyte show a good performance at a discharge rate below C/2. [Copyright &y& Elsevier]

Abstract: Three new poly(4,4-dialkylcyclopentadithiophene (PDOCPT) derivatives, poly(4,4-dialkylcyclopentadithiophene-co-pyridine) (PDOCPTPy), poly(4,4-dialkylcyclopentadithiophene-co-phenanthroline) (PDOCPTPh), and poly(cyclopenta[2,1-b:3,4-b′]dithiophen-4-one) (PDOCPTCK) were prepared. They were synthesized form the Stille coupling of 2,7-bis-trimethyltin-4,4-dialkylcyclopentadithiophene with dibromopyridine and dibromophenanthroline, respectively. They are soluble in organic solvents, such as CHCl3 and Toluene. The absorption thresholds of these two polymers are 500 and 650nm for PDOCPTPy and PDOCPTPh, respectively. The electronic absorption data suggested that the band gap energy of copolymer will fall in-between the individual homopolymers. This may give a cue on how to prepare soluble conjugated polymers with desirable band gap energy. [Copyright &y& Elsevier]

Abstract: Highly conducting porous polymer electrolytes comprised of poly(vinylidene-fluoride-co-hexafluoropropylene) (PVdF-HFP), polyethylene oxide-co-polypropylene oxide-co-polyethylene oxide (P123), ethylene carbonate (EC), propylene carbonate (PC), and LiClO4 were fabricated. The PVdF-HFP/P123 hybrid polymer membranes were made with a phase inverse method and the electrolyte solution uptake was carried out in glove box to avoid the moisture contamination. It was found that when a small amount of polymer surfactant (P123) was blended into the PVdF-HFP, mesopores with well-defined sizes were formed. Impedance spectroscopy showed that the room temperature conductivity of (PVdF-HFP)/P123 polymer electrolytes increased as the content of P123 increased up to 4×10−3 S/cm. Nitrogen adsorption isotherms, electrolyte solution uptake, porosity measurements, and SEM micrographs showed that the enhanced conductivity was due to increase the pore volume, pore density, and electrolyte uptake. The highest conduction was found when the weight ratio of P123 to PVdF-HFP was 70%, when big channels were formed in the hybrid polymer membrane. Furthermore, blending P123 in PVDF-HFP reduced the pore size of polymer membrane, therefore, the solution leakage was also reduced. These polymer electrolytes were stable up to 4.5V (vs Li/Li+) and the performance of the model lithium ion battery made by sandwiching the polymer electrolyte between a LiCoO2 anode and a MCMB cathode, showed great promise for the use of these polymer electrolytes in lithium ion batteries. [Copyright &y& Elsevier]

Abstract: Starting from 2,6-bis-(3-octylthiophene-2yl)-pyridine, two new poly(alkylthiophene) derivatives, POTPyOT and POTPy, containing pyridine in the backbone were prepared from nickel(0)-mediated Stille coupling or by palladium-catalyzed Yamamoto coupling. These polymers exhibited good solubility in common organic solvents, thermal stability up to 400°C, and facile film formation. They were amorphous and give strong luminescence both in CHCl3 solution and solid state film. The polymers emitted blue light in solution with photoluminescence (PL) emission maximum at 420–484nm and green light with PL emission maximum at 500–514nm in thin films. These polymers showed a reversible redox reaction at potential from 0 to 1.3V (vs. SCE). Nevertheless, the reduced form of the polymer was very unstable; it decomposed in the presence of oxygen or water. The emission and UV–vis absorption of the polymer were influenced by the solvent polarity, protonation, and acid–base treatment. These may be the results of the stabilization of the polar excited state by solvation and the change of the conformation in polymer backbone. Electroluminescence (EL) was achieved from a single-layer PLED with the configuration of ITO/POTPyOT/Al. The turn-on voltage of the device is 10V and the λ max (550nm) of the EL is voltage independent. [Copyright &y& Elsevier]

The morphology and conductivity of indium/tin oxide (ITO) film have a large impact on the performance of light emitting diode (LED) devices using ITO as an anode. Atomic Force Microscope and current image tunneling spectroscopy (CITS) were used to probe the surface morphology and scanning tunneling spectroscopy (STS) of ITO surface. The morphology of all ITO films studied revealed a spherical aggregation with various grain sizes of 20~50 nm, depends on clean methods. It was also found that the conductivity of ITO films is related to film thickness. In general, thicker film shows higher conductivity. Nevertheless, the conductivity within a single grain is very homogeneous. On the other hand, the topographies of poly(N-(4-sulfophenyl)aniline (PSA) films revealed a rod-shaped aggregation with a diameter of 50 nm. The corresponding CITS images revealed conducting islands with irregular shape and size. The conductivity within a single polymer rod is not homogeneous. [ABSTRACT FROM AUTHOR]

The physicochemical properties and photo catalytic activity of transition metal-loaded TiO2 catalysts were studied. The transition metal was deposited on TiO2 via post-hydrothermal synthesis and photo-assisted reduction/impregnation. The structure of TiO2 is preserved upon adding Pd, Cr, and Ag into it. Nevertheless, the structure of TiO2 was destroyed when reacted with silicotungstic acid (Si-W). As a consequence, under the irradiation of visible light, the Pd and Cr loaded TiO2 showed higher photo catalytic activity compared to pristine TiO2 and Si-W loaded TiO2 has no catalytic activity, although the threshold absorptions of all metal loaded TiO2 is similar to that of pure TiO2. Transition metal was homogeneously coated on the TiO2 particles and there is no phase separation between metal salts and TiO2 as revealed with scanning electron micrographs (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) data. X-ray photoelectron spectroscopy (XPS) spectra showed that all metals in metal loaded TiO2 presented as an ionic state with slightly reduction compared to the metal in metal salt used in the reaction, probably due to the interaction with TiO2. These results suggested that the crystallinity was important for the photo catalytic activity of TiO2 based catalysts and the function of transition metal is to increase the electron-hole recombination time, therefore increase the catalytic activity. [Copyright &y& Elsevier]

Water-soluble conducting poly(2-(3thienyloxy)ethanesulfonic acid) (PTOESA)/V2O5 nanocomposite, (PTOESA)xV2O5, was prepared by simply mixing PTOESA with V2O5 wet gel at room temperature. XRD data showed that the interlayer spacings of (PTOESA)xV2O5 films are 14.0±1.5 Å and increased as the polymer content increased. These values are consistent with the insertion of polythiophene chains into the V2O5 layer gallery. The formation of alternative layers of PTOESA and V2O5 was further supported by depth profile SIMS analyses. Cyclic voltammograms of (PTOESA)xV2O5 film showed two pairs of redox peaks with colors varying from orange, yellowish green, green, to purple blue, depending on the stoichiometry of the nanocomposites. Moreover, a synergetic effect was observed on the electrochromic properties of these nanocomposites. It was found that the optical contrast (ΔOD) of the composites is better than those of PTOESA and V2O5 at the film thickness from 150 to 500 nm. The oxidation optical response time of (PTOESA)xV2O5 is independent of the stoichiometry and falls in between those of PTOESA and V2O5. At higher polymer content (x>0.5), the reduction optical response time of (PTOESA)xV2O5 is smaller than those of PTOESA and V2O5. Variable temperature conductivity data showed that the conductivity of (PTOESA)xV2O5 films increased as temperature increased, characteristic of thermal activated behavior, which was dominated by the interparticle contact resistance. The room-temperature conductivity of water-soluble (PTOESA)xV2O5 films was in between those of PTOESA and V2O5 xerogel and higher conductivity was found in the composite with lower polymer content. The anomalous conductivity of (PTOESA)xV2O5 with high PTOESA content may be due to the reason that the higher the polymer content, the bigger the grain size of (PTOESA)xV2O5 film as revealed with scanning electron microscopy and AFM micrographs. [Copyright &y& Elsevier]

A new type of TiO2 film is prepared by insertion of a bifunctional silane agent bearing sulfonate group in between TiO2 and the substrate. The alkoxyl silane is bound to the surface of the substrate via molecular self-absorption and the terminal sulfonate group is used to grasp the TiO2 particles to form stable film. Modifications of the TiO2 catalysts, such as metal deposition and calcination, were carried out simply with the films on substrates. The activity of this new type TiO2 film is tested by catalytic photodegrading of salicylic acid in water. It was found that when the particle size of the TiO2 is smaller than 200 nm, the catalytic activities of the TiO2 films deposited on sulfonate-grafted glass are better than those of the films deposited on unmodified glass. Increasing the crystallinity of TiO2 particles, depositing the precious metals (such as Au or Pd) on TiO2, or aging the TiO2 film will enhance the catalytic activity of TiO2. The enhancement is better for the film deposited on sulfonate-grafted substrates. In spite of calcining the TiO2 film decreased its catalytic activity due to the particle aggregation, the decrease is also less significant for TiO2 films deposited on sulfonate-grafted substrates. The sulfonate group can be regarded as a dispersion agent for TiO2 film deposition and calcination. [Copyright &y& Elsevier]

An exquisite, engineering of two poor hole transporting materials (HTMs, SnO, and PDTON) to form an excellent double‐layered HTL (SnO/PDTON) for inverted tin‐perovskite solar modules (TPSMs) is developed. SnO/PDTON has better photovoltaic performance than the commonly used PEDOT:PSS HTM when large‐area TPSMs are fabricated. Thermally evaporated SnO (that is a simple, available oxide with high hole mobility, good transparency, and adjustable frontier orbitals energy levels) film is used as a main hole transporting layer (HTL). Amphiphilic polymer PDTON (having the amine and ether groups on the side chains) film is used as a Co‐HTL, cross‐linker, passivator, and interface modification agent, as unveiled various physicochemical studies. Double‐layered SnO/PDTON with a flat morphology and good affinity toward perovskite precursor solution creates also a proper surface for depositing large‐area, high‐quality TPsk film. Therefore, TPSM (25.2 cm2 active area on 10 cm × 10 cm ITO substrate) based on double‐layered SnO/PDTON HTL achieving an efficiency over 10% with a negligible current hysteresis is reported for the first time. This study emphasizes not only the exquisite design of combining the specific characteristics of two prosaic HTMs to become a good double‐layered HTL but also gives a direction toward fabricating TPSMs to be applied in all‐perovskite tandem solar module. [ABSTRACT FROM AUTHOR]

Five monochloro- s -triazinyl reactive dyes (MCT) and five m -carboxypyridium- s -triazinyl reactive dyes (NTR) were synthesised with the same red chromophore bearing an –NHCN, –OCH 3 , –CH 3 NSO 2 CH 3 , – N -methyl phenyl or –OH group as 'second-leg' substituents. A kinetic study of the hydrolysis of these dyes was conducted, and the rate constant (k obs) and half-life time values were determined. The k obs of the MCT and NTR dyes was found to follow the order –OCH 3 > –CH 3 NSO 2 CH 3 > – N -methyl phenyl > –NHCN > –OH, which was approximately in agreement with the values obtained for the Hammett substituent constants. Overall, the higher the electron-donating property of the substituent on meta -position to the leaving group in the triazine ring, the lower the hydrolysis rate constant. • Chloro substituent in the MCT dyes was replaced by nicotinic acid, the reactivity was enhanced. • The order of reactivity of dyes is related to the electronic effect of the substituent. • The order of k obs was in agreement with the values of Hammett substituent constants. [ABSTRACT FROM AUTHOR]

Reports on the encapsulation of conducting structures in ordered, insulating host systems as a promising approach toward controlled electronic access to individual nanometer-sized objects. Use of zeolites as host; Polymerization of acrylonitrile monomers; Role of host in ordering of carbon structure.

Discusses the preparation of conducting filaments of polyaniline in the three-manometer hexagonal channel system of the aluminosilicate MCM-41. Processes leading to encapsulated polyaniline filaments; Indications of spectroscopic data and chromatography; Processes involved representing a step toward design of manometer electronic devices.

Three N,N′ -diaryl-4-amino-azobenzene derivatives containing donor (D) and acceptor (A) moieties have been synthesized for light harvesting. Their optical and electronic characteristics have been analyzed to determine the optical band gap between highest occupied molecular orbital (HOMO) and lowest occupied molecular orbital (LUMO). The electrochemical properties and electrochemical redox potential of the triarylamines exhibited linear relationship with respect to the Hammett equation. The stability of the oxidation products and spectral changes with different applied potentials were monitored with UV–vis spectroelectrochemical investigations and DFT calculations. A solution-processed organic photovoltaic cell employing N,N′ -ditolyl-4-aminoazobenzene (DTAA) mixed with PC 60 BM produced a power conversion efficiency (PCE) of 0.28% under 1 sun illumination. [ABSTRACT FROM AUTHOR]

Highlights: [•] Stable PANI/HFIP and PEDOT/HFIP solution are prepared by dissolving doped polymer in hexafluoro-isopropanol (HFIP). [•] PANI or PEDOT film deposited on FTO as a counter electrode was fabricated simply by spin-coating or casting method. [•] DSC device based on PEDOT/FTO counter electrode, CYC-B11 dye, and electrolyte has the efficiency of 9.0%. [ABSTRACT FROM AUTHOR]

Abstract: Solid-state dye-sensitized solar cells (ss-DSCs) are fabricated using Z907 or its thiophene derivative, CYC-B11, as a dye, and poly(3-hexylthiophene) (P3HT) or (2,2′,7,7′-tetrakis-(N,N-di-p-methoxyphenylamine)9,9′)-spirobifluorene (OMeTAD) as a hole transport material (HTM). The effect of the structural compatibility of dye molecules with HTM on device performance is investigated. The CYC-B11/P3HT device has a much higher short-circuit current density than Z907/P3HT and CYC-B11/OMeTAD devices. Results from the incident photo-to-electron conversion efficiency and impedance measurements support the use of P3HT, in place of OMeTAD, as HTM markedly increases the photocurrent throughout the absorption spectrum of CYC-B11 and significantly reduces the charge-transfer resistance at the TiO2/dye/HTM interface. As a result, the CYC-B11/P3HT ss-DSC that is fabricated from a thin (0.5 μm) mesoporous TiO2 layer exhibits an outstanding power conversion efficiency of 3.66%. [Copyright &y& Elsevier]

Perovskite solar cells (PSCs) have received great attention due to their outstanding performance and their low processing costs. To boost their performance, one approach is to reinforce the built‐in electric field (BEF) to promote oriented carrier transport. The BEF is maximized by reinforcing the work function difference between cathode and anode (Δμ1) and increasing the work function difference between lower and upper surfaces of perovskite film (Δμ2) via introduction of electric dipole molecules, denoted as PTFCN and CF3BACl. The synergistic reinforcement of BEF improves charge transport and collection, and realizes markedly high photovoltaic performances with the best power conversion efficiency (PCE) up to 21.5%, a growth of 15.6% as compared to the control device, which is higher than the superposition of improvements achieved by either raising Δμ1 or Δμ2. Importantly, dual‐functional CF3BACl not only supplies dipole effect for tuning the surface potential of perovskite but offers hydrophobic trifluoride group toward the long‐term stable unencapsulated PSCs retaining more than 95% PCE after storing 2000 h under ambient conditions. This work demonstrates the synergistic effect of Δμ1 and Δμ2, providing an effective strategy for the further development of PSC in terms of photovoltaic conversion and stability. [ABSTRACT FROM AUTHOR]

An antisolvent (iodobenzene, IB) was used to assist the formation of closely packed CH 3 NH 3 PbI 3 (MAPbI 3 ) thin films during the one-step spin-coating process using different volumes of IB. The morphological, structural, optical and excitonic properties of MAPbI 3 thin films were analyzed using a contact-mode atomic-force microscope, X-ray diffractometer, broadband absorbance spectrometer and optical microscope-based time-resolved photoluminescence spectrometer. The properties of the resultant MAPbI 3 thin films can be manipulated by using different IB volumes, which dominates the device performance of MAPbI 3 based photovoltaic cells. The experimental results show that the grain size (or particle size) of MAPbI 3 thin films influences the collection of photoexcited carriers and the contact at the 6,6-Phenyl C 61 butyric acid methyl ester (PCBM)/MAPbI 3 interface, thereby resulting in a trade-off between the fill factor (FF) and short-circuit current density (J SC ). In addition, it is predicted that the power conversion efficiency (PCE) can be further improved by increasing the crystallinity of the MAPbI 3 thin film while keeping the small grain size. [ABSTRACT FROM AUTHOR]

Four heterocyclic spiro-type hole transporting materials (HTMs) carrying a spiro[fluorene-9,9′-xanthene] (SFX) (SFX-TPAM and SFX-TPA) or spiro[fluorene-9,9′-thioxanthene] (SFT) unit (SFT-TPAM and SFT-TPA) were synthesized through a low-cost facile route with high yields for perovskite solar cell (PSC) applications. In terms of absorption, these four compounds in the film state are all transparent at wavelengths longer than 430 nm, which is beneficial for allowing visible light to reach the perovskite active layer without being absorbed by the hole transporting layer (HTL). The photovoltaic performance of the inverted PSCs based on these small molecular HTMs with the device architecture of glass/ITO/HTL/CH3NH3PbI3/C60/BCP/Ag was tested. Only SFX-TPAM had its highest occupied molecular orbital (HOMO) level matched with the valence band of CH3NH3PbI3. The inverted PSC based on a dopant-free SFX-TPAM HTL achieves a power conversion efficiency of 10.23% under the illumination of standard one sun lighting, which is better than that (8.17%) of the cell based on dopant-free spiro-OMeTAD. The better photovoltaic performance of SFX-TPAM compared to spiro-OMeTAD may be due to the MAPbI3 film deposited on it having better quality. These results indicate that the facilely synthesized, low-cost SFX based small molecules can be used as the HTMs for PSCs. [ABSTRACT FROM AUTHOR]

Comprehensive studies were carried out to explore the roles of phenyl-C 61 -butyric acid methyl ester (PCBM) thin films in inverted-type CH 3 NH 3 PbI 3 (MAPbI 3 ) based photovoltaics, including the surface morphologies, transmittance spectra, photoluminescence spectra, X-ray diffraction (XRD) patterns, Raman scattering spectra and thin-film residual stress analysis. The reduction in the photoluminescence line width indicates that the crystallinity of the MAPbI 3 thin film can be increased by covering it with the PCBM thin film. The XRD patterns and Raman scattering spectra show a reduction in the compressive stress of MAPbI 3 thin film when covered by the PCBM thin film. In addition, it is noted that the residual stress at the contact interface between the hydrophilic MAPbI 3 and the hydrophobic PCBM can be ignored as confirmed by the results obtained with a home-made Twyman-Green interferometer. Consequently, the superior optoelectronic properties of the perovskite materials, as well as the use of a multifunctional fullerene-based thin film as the capping layer allow for the high-efficiency perovskite photovoltaics. [ABSTRACT FROM AUTHOR]

Comprehensive studies were carried out to explore the thickness-dependent characteristics of thermally evaporated C 60 thin films. The structural, optical, electronic and surface properties of the resultant C 60 thin films were analyzed using Raman scattering spectrometry, photoluminescence spectroscopy, absorbance spectroscopy, photoelectron emission spectrometry and water droplet contact angle measurement. The experimental results show that the thickness of the C 60 thin film has a decisive impact on the photovoltaic performance of CH 3 NH 3 PbI 3 based solar cells in terms of open-circuit voltage (V OC ), short-circuit current density (J SC ) and fill factor (FF). In the case of the 2.5 nm-thick C 60 film, the solar cells have the better V OC and J SC , as the results of the lower electron affinity and higher transparency. The FF of the solar cell is related to the coverage of C 60 on the transparent conductive electrode (TCE) and the CH 3 NH 3 PbI 3 perovskite continuity. Consequently, the photovoltaic performance can be expected to be improved by using a smooth TCE. [ABSTRACT FROM AUTHOR]

A series of alcohols (methanol, ethanol and isopropyl alcohol) were added to poly(3,4-ethylenedioxythiophene): (polystyrene sulfonate) (PEDOT: PSS) aqueous solutions in order to manipulate the molecular structure of the PEDOT chains in PEDOT: PSS hole transporting materials (HTMs) and thus to improve the power conversion efficiency of CH 3 NH 3 PbI 3 based solar cells. The structural and electronic characteristics of the resultant PEDOT: PSS HTMs were analyzed using atomic-force microscopy, contact angle measurement, Raman scattering spectrometry and photoelectron spectrometry. The properties of the PEDOT: PSS thin films could be controlled by tuning the viscosity of the PEDOT: PSS solutions. High viscosity PEDOT: PSS solutions resulted in linear structured PEDOT chains, which increased the work function of the PEDOT: PSS HTMs thereby improving the open-circuit voltage of the CH 3 NH 3 PbI 3 solar cells. The surface roughness and surface free energy of the PEDOT: PSS HTMs influence the structural properties of CH 3 NH 3 PbI 3 thin films, which determines the exciton dissociation at the CH 3 NH 3 PbI 3 /PEDOT: PSS interface (short-circuit current density) and the carrier recombination at the CH 3 NH 3 PbI 3 /[6,6]-phenyl-C61-butyric acid methyl ester (PC 61 BM) interface (fill factor). In addition, it is predicted that the power conversion efficiency can be further improved by increasing the crystallinity of the CH 3 NH 3 PbI 3 thin film. [ABSTRACT FROM AUTHOR]

An international round-robin inter-comparison of the spectral responsivity (SR) and current-voltage (I-V) characteristics for dye-sensitized solar cells (DSCs) and crystalline silicon solar cells is reported for the first time. The crystalline silicon cells with various spectral responsivities were also calibrated by AIST to validate this round-robin activity. On the basis of the remarkable consistency in Pmax (within ±1.4% among participants) and Isc (within ±1.2% compared to the primary calibration of AIST) of the silicon specimens, the discrepancy in the SR and photovoltaic parameters of five DSCs among three national laboratories can be verified and diagnosed. Recommendations about sample packages, SR and I-V measurement methods as well as the inter-comparison protocol for improving the performance characterization of the mesoscopic DSCs are presented according to the consolidated data and the experience of the participants. [ABSTRACT FROM AUTHOR]

A series of nonpolar antisolvents (chlorobenzene, bromobenzene, iodobenzene and toluene) were used to assist in the formation of smooth and crystalline CH 3 NH 3 PbI 3 thin films by a one-step spin-coating method. The structural, optical and excitonic characteristics of the resultant CH 3 NH 3 PI 3 thin films were analyzed using an atomic-force microscope, X-ray diffractometer, absorbance spectrum, photoluminescence (PL) spectrum, time-resolved PL and temperature-dependent PL. The properties of the CH 3 NH 3 PbI 3 thin films are dependent on the relative polarity and boiling point of the nonpolar antisolvents used in the washing treatment process. The interplay between nucleation (relative polarity) and crystal growth (boiling point) during the formation of CH 3 NH 3 PbI 3 thin films influences the short-circuit current density (J SC ) and power conversion efficiency (PCE) of the corresponding solar cells. The experimental results demonstrate that iodobenzene can be substituted for toluene as a more efficient antisolvent in the washing treatment process during the fabrication of CH 3 NH 3 PbI 3 thin films. In addition, it is predicted that the J SC and PCE can be further improved by increasing the crystallinity of the CH 3 NH 3 PbI 3 thin film. [ABSTRACT FROM AUTHOR]

The multicrystalline grain size of CH 3 NH 3 PbI 3 thin films can be manipulated by using different precursor concentrations which dominate the competition between the nucleation and crystal growth during the one-step spin-coating process with the toluene washing treatment. A comprehensive study was carried out to explore the correlation between the structural properties and the exciton dynamics in CH 3 NH 3 PbI 3 thin films fabricated using various precursor concentrations from 1.25 M to 1.65 M. The experimental results show that the precursor concentration influences the grain size and exciton dynamics of the resultant CH 3 NH 3 PbI 3 thin films which were fabricated on top of poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate/ITO/glass substrates. The higher average power conversion efficiency (PCE) of 13.66% achieved can be explained as being due to the formation of a larger CH 3 NH 3 PbI 3 grain size which thus results in higher photocurrent generation and lower voltage loss. It is predicted that the PCE can be further improved when the voltage loss across the CH 3 NH 3 PbI 3 thin film is minimized. [ABSTRACT FROM AUTHOR]

Inverted-type perovskite solar cells offer the potential of fabrication by low-temperature solution processing as an alternative to conventional-type perovskite solar cells. PEDOT:PSS is commonly used as the hole transport layer (HTL), but its acidic nature may damage the reliability and stability of the photovoltaic device. In this study, we demonstrate the use of MoO x and WO x HTLs as an alternative to PEDOT:PSS for planar CH 3 NH 3 PbI 3 perovskite solar cells. Furthermore, the MoO x and WO x HTLs are treated using a UV-ozone treatment to improve the surface coverage of the perovskite layer. The resultant conversion efficiency (PCE) for the best cells at AM1.5G illumination with a shadow mask was 13.1%. [ABSTRACT FROM AUTHOR]

Cobalt selenide (Co 0.85 Se) and nickel selenide (Ni 0.85 Se) hierarchical thin films assembled using by nanosheets and nanoparticles, respectively, were fabricated in situ on fluorine-doped tin oxide substrates in a ligand-free environment to prepare counter electrodes (CEs) for dye-sensitized solar cells (DSSCs) consisting of a N719-sensitized nanocrystalline TiO 2 film. The Co 0.85 Se- and Ni 0 . 85 Se-based CEs were rapidly synthesized via a microwave-assisted one-step method at 170 °C within a short reaction time of 10 min. The morphology and structure of the Co 0.85 Se and Ni 0.85 Se hierarchical thin films were characterized by means of scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The results of electrochemical impedance spectroscopy, cyclic voltammetry, and Tafel polarization measurements showed that both CEs exhibited good electrocatalytic activity and I − /I 3 − redox reactions and much lower charge-transfer resistance. A power conversion efficiency (PCE) of 8.58% for the Co 0.85 Se CE-based solar cell was obtained, which is comparable to that of cells using Pt CEs (8.57%); 7.09% PCE was obtained for the Ni 0.85 Se-based CE. The results suggest that in situ-prepared Co 0.85 Se-based CEs could be a promising alternative to Pt-based CEs for DSSCs. [ABSTRACT FROM AUTHOR]

Doping metal-ion into TiO 2 materials is an effective method for enhancing the performance of dye-sensitized solar cells (DSSCs). In order to develop materials that are easy to produce even in industrial quantities, we established a facile method by hydrothermal synthesis and subsequent heat treatment to prepare bismuth doped titanium dioxide nanofibers (Bi-doped TiO 2 NFs). At first, we adopt Bi-doped TiO 2 NFs as the working electrode to further study in DSSCs. Serving as working electrode, Bi-doped TiO 2 NFs can remarkably improve open-circuit voltage ( V OC ). The V OC was significantly enhanced from 0.633 V to 0.800 V compared with pristine TiO 2 does. However, this leads to a smaller J SC and a poorer overall performance for such devices. In order to improve the performance of DSSCs, we adopt Bi-doped TiO 2 NFs as the scattering layer of DSSCs, and various thicknesses of meso-TiO 2 nanoparticles (meso-TiO 2 NPs) were used as working electrode to increase the short-circuit current ( J SC ). The incorporated Bi-doped TiO 2 NFs can help the electron transport and may reduce the possibility for electron–hole recombination. After optimizing the device’s parameter, the overall performance of the meso-TiO 2 NPs/Bi-doped TiO 2 NFs devices was dominated by J SC until a maximum efficiency was attained with a meso-TiO 2 NPs thickness of 12 μm. Such optimized DSSCs exhibited high open circuit voltage of 0.787 V, high fill factor of 78.2%, and high power conversion efficiency of 8.89%. [ABSTRACT FROM AUTHOR]

A phase-pure mixed-organic-cation perovskite absorber (MOC-PA) was fabricated by a one-step spin-coating process with a toluene washing treatment, and the structural, optical and excitonic properties of the resultant MOC-PAs were then characterized by scanning electron microscopy, X-ray diffractometry, absorbance spectrometer, and time-resolved photoluminescence. The averaged power conversion efficiency (PCE) of inverted phase-pure MOC-PA based photovoltaics could be improved from 12.21% to 13.28% by tailing the surface roughness of the poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) thin film from 1.43 nm to 1.84 nm. The improved PCE is mainly due to the increased short-circuit current density ( J SC ) which is attributed to the improvement of the exciton dissociation, as confirmed by photoluminescence experiments. In addition, the experimental results indicate that the PCE can be further improved by increasing the crystallinity of MOC-PAs. [ABSTRACT FROM AUTHOR]

Sputtering made ZnO thin film was used as an electron-transport layer in a regular planar perovskite solar cell based on high quality CH3NH3PbI3 absorber prepared with a two-step spin-coating. An efficiency up to 15.9% under AM 1.5G irradiation is achieved for the cell based on ZnO film fabricated under Ar working gas. The atmosphere of the sputtering chamber can tune the surface electronic properties (band structure) of the resulting ZnO thin film and therefore the photovoltaic performance of the corresponding perovskite solar cell. Precise surface engineering of ZnO thin film was found to be one of the key steps to fabricate ZnO based regular planar perovskite solar cell with high power conversion efficiency. Sputtering method is proved to be one of the excellent techniques to prepare ZnO thin film with controllable properties. [ABSTRACT FROM AUTHOR]

ABSTRACT Two D-π-A copolymers, based on the benzo[1,2- b:4,5- b′]-dithiophene (BDT) as a donor unit and benzo-quinoxaline (BQ) or pyrido-quinoxaline (PQ) analog as an acceptor (PBDT-TBQ and PBDT-TPQ), were designed and synthesized as a p-type material for bulk heterojunction (BHJ) photovoltaic cells. When compared with the PBDT-TBQ polymer, PBDT-TPQ exhibits stronger intramolecular charge transfer, showing a broad absorption coverage at the red region and narrower optical bandgap of 1.69 eV with a relatively low-lying HOMO energy level at −5.24 eV. The experimental data show that the exciton dissociation efficiency of PBDT-TPQ:PC71BM blend is better than that in the PBDT-TBQ:PC71BM blend, which can explain that the IPCE spectra of the PBDT-TPQ-based solar cell were higher than that of the PBDT-TBQ-based solar cell. The maximum efficiency of PBDT-TPQ-based device reaches 4.40% which is much higher than 2.45% of PBDT-TBQ, indicating that PQ unit is a promising electron-acceptor moiety for BHJ solar cells. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 1822-1833 [ABSTRACT FROM AUTHOR]

Two fused-thiophene-containing ruthenium sensitizers, [Ru(Hdcbpy)(ottip)(NCS)2]- ·0.5[H]+ ·0.5[N(C4H9)4]+ [ Z1, H2dcbpy = 4,4′-dicarboxy-2,2′-bipyridine, ottip = 2-(5-octylthieno[3,2- b]thiophen-2-yl)-1 H-imidazo[4,5- f][1,10]phenanthroline] and [Ru(Hdcbpy)(odttip)(NCS)2]- ·0.5[H]+ ·0.5[N(C4H9)4]+ { Z2, odttip = 2-[6-octyldithieno(3,2- b:2′,3′)thiophen-2-yl]-1 H-imidazo[4,5- f][1,10]phenanthroline}, were designed for use in dye-sensitized solar cell (DSSC) applications. The fused-thiophene-based Z1 and Z2 have stronger light-harvesting capabilities compared with a non-fused-thiophene analog, [Ru(Hdcbpy)(otip)(NCS)2]- ·0.5[H]+ ·0.5[N(C4H9)4]+ [ JF-2t, otip = 2-(5-octylthiophen-2-yl)-1 H-imidazo[4,5- f][1,10]phenanthroline], and a standard N3 dye. The power-conversion efficiency of the Z1- and Z2-sensitized solar cells were superior (8.70 % and 8.15 %) to JF-2t- and N3-sensitized solar cells (7.85 and 7.40 %, respectively) under standard AM1.5G full sunlight irradiation. The photovoltaic performance of Z1 was better than Z2, primarily owing to the fact that Z1-based cells have a higher level of dye loading and less charge recombination, as seen from the electrochemical impedance spectroscopy data. This study not only demonstrates the excellent power-conversion efficiency of new fused-thiophene ruthenium sensitizers, but also points to the promise that fused-thiophene antennas might be a useful molecule in the engineering of ruthenium dyes for DSSCs. [ABSTRACT FROM AUTHOR]

A comprehensive study was carried out to understand the influence of organic cations on high-performance CH 3 NH 3 PbI 3 based photovoltaics. Scanning electron microscope, X-ray diffractometer, Hall measurement, absorbance spectrum, photoluminescence (PL) spectrum and nanosecond time-resolved PL measurements were used to explore the structural, electrical, optical and excitonic characteristics of CH 3 NH 3 PbI 3 thin films fabricated under different thermal annealing temperatures from 60 °C to 140 °C. The decrease in the open-circuit voltage ( V OC ) with an increase in the thermal annealing temperature can be explained as due to the reduced work function of the CH 3 NH 3 PbI 3 thin film. The short-circuit current density ( J SC ) of the CH 3 NH 3 PbI 3 based photovoltaics is dependent on the efficiencies of light absorption and carrier collection, which results in an optimized J SC when the thermal annealing temperature is 120 °C. The atomistic interaction between the organic cations and Pb–I framework strongly influences the absorbance of CH 3 NH 3 PbI 3 thin films, as confirmed by the libration of CH 3 NH 3 cations shown by Raman scattering spectroscopy. In addition, the experimental results indicate that the power conversion efficiency can be further improved when the absorption strength of the CH 3 NH 3 PbI 3 thin film and the energy-level alignment of each photovoltaic layer are simultaneously fulfilled. [ABSTRACT FROM AUTHOR]

Two diketopyrrolopyrrole (DPP) containing D–π–A organic dyes, named as TEDBn and TEDTh were prepared. Their optical, electrochemical and photophysical properties were investigated and their application in dye-sensitized solar cells (DSCs) was demonstrated. The broaden absorption and low-energy λ max of DPP containing dyes were contributed from DPP bridge and EDOT π-conjugated moiety. Compared to TEDTh, TEDBn has smaller absorption coefficient and higher optical bandgap. Nevertheless the power conversion efficiency (PCE) of TEDBn based DSC is 7.2% which is larger than that of TEDTh based DSC and 90% of N719 based cell. The higher PCE of TEDBn based device originates from both higher open-circuit voltage (V OC ) and short-circuit current (J SC ). Femtosecond time-resolved photoluminescence data show that the electron injection at TEDBn/TiO 2 is more efficient than that at TEDTh/TiO 2 interface, resulting in higher J SC (and IPCE) of TEDBn based DSC. Density function theory (DFT) calculations revealed that TEDBn is a linear structure which leads to higher dye loading on TiO 2 than TEDTh which featured a bend conformation, better TiO 2 surface coverage, resulting in larger V OC . Therefore, the overall efficiency of the cell sensitized by TEDBn is better than that the devices based on TEDTh. [ABSTRACT FROM AUTHOR]

This work studies annealing effects of the CH 3 NH 3 PbI 3 perovskite film for solar cell applications by time-resolved photoluminescence (TR-PL) spectra. The different thermal annealing temperatures process influences the quality and exciton lifetime of the CH 3 NH 3 PbI 3 perovskite film and importantly the device performance. The CH 3 NH 3 PbI 3 perovskite film of the optimal thermal annealing temperatures (100 °C) would significantly extended exciton lifetime and yield a higher open-circuit voltage, with short-circuit current density ( J SC ) = 21.58 mA/cm 2 , open-circuit voltage ( V OC ) = 0.84 V, fill factor (FF) = 61.4%, and η = 11.12%, respectively. [ABSTRACT FROM AUTHOR]

The open-circuit voltage of CH 3 NH 3 PbI 3 based photovoltaics was enhanced from 0.77 V to 0.9 V, which resulted in an improvement of the average power conversion efficiency from 5.63% to 11.74% achieved by tuning the work function of the poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) hole transport layer. The higher work function of the PEDOT:PSS (1:20 wt%) thin film, as compared to the PEDOT:PSS (1:6 wt%) and PEDOT:PSS (1:2.5 wt%) thin films, was observed using photoelectron spectrometer. The carrier density of PEDOT was obtained by analyzing the transmittance spectrum of PEDOT:PSS/glass with the transfer matrix method. The Drude model can be used to explain the increased work function of the PEDOT:PSS thin film obtained by decreasing the ratio of PEDOT to PSS. The increased carrier density of the PEDOT in PEDOT:PSS thin films originated from conformational changes in the PEDOT chains as confirmed by Raman scattering spectroscopy. [ABSTRACT FROM AUTHOR]

A comprehensive study was carried out to understand the formation of a crystalline tri-iodide perovskite absorber (TPA) on top of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). Scanning electron microscopy, two-dimensional X-ray diffraction and nanosecond time-resolved photoluminescence were used to explore the correlation between the surface morphology and the exciton lifetime in TPA fabricated with and without the in-situ toluene washing treatment. The toluene washing treatment decreases the crystallinity (exciton lifetime) of TPA and improves the TPA coverage on the non-crystalline PEDOT:PSS surface. The high average power conversion efficiency (PCE) of 10.61% achieved can be explained as due to the efficient exciton dissociation at the interface between the TPA and the PEDOT:PSS. The experimental results show that the PCE can be further improved when the crystallinity of TPA and the TPA coverage on PEDOT:PSS are simultaneously optimized. [ABSTRACT FROM AUTHOR]

Comprehensive studies were carried out to understand the thickness effects of ZnO thin films for tri-iodide perovskite absorber (TPA) based photovoltaics, including the absorption spectrum, photoluminescence, nanosecond time-resolved photoluminescence (NTRPL), and photo-induced absorption (PIA) of TPA/ZnO/ITO/glass. These were carried out in order to explore the Urbach energy of TPA films and the exciton dissociation at the interface between TPA and ZnO. The results show that the thickness of the ZnO thin film significantly influences the photovoltaic performance in terms of open-circuit voltage ( V OC ), fill factor (FF), and short-circuit current density ( J SC ). In the case of the thicker ZnO film, the photovoltaics have the better FF and V oc , as a result of the smaller electron recombination. This means that a thicker ZnO film can block the electron recombination from the Fermi level of the ITO to the valance band of the TPA. On the other hand, the thicker ZnO film results in a higher J SC due to the better exciton dissociation at the interface between TPA and ZnO, which means that the electron mobility of the thicker ZnO is higher. Consequently, the photovoltaic performance can be expected to be improved by using a transparent cathode electrode with high conductivity and electron mobility. [ABSTRACT FROM AUTHOR]

Raman spectroscopy and photoluminescence (PL) were used to investigate the improved short-circuit current density ( J SC ) of CdS/CdSe quantum dot (QD)-sensitized solar cells with multi-walled carbon nanotubes (MWCNTs). Raman and PL experiments were carried out in order to explore the hot-electron and cold-electron injections, respectively. The experimental results showed that the concentration of MWCNTs influences the hot-electron and cold-electron injections from CdS/CdSe QDs to TiO 2 nanoparticles. Therefore, the improved J SC in CdS/CdSe QD-sensitized solar cells can be explained as due to the better electron injections. [ABSTRACT FROM AUTHOR]

In this work, low resistivity and high transmittance fluorine doped tin oxide (FTO) and Li doped FTO (LIFTO) films are prepared by spray pyrolysis and the effect of hazes of FTO and LIFTO on the performance of dye-sensitized solar cells (DSSCs) is studied. Influences of different parameters such as molar ratio of F/Sn, Li + and F − dual ion doping, substrate temperature and carrier gas on the optical, electrical, grain structural and surface morphological characteristics of the LIFTO films are evaluated in detail. It is found that with the increase of dual ion doping concentrations of Li + and F − from 0.0 to 0.05 M, the resistivity of the LIFTO film increases from 4.4 × 10 − 4 to 7.8 × 10 − 4 Ω·cm, the transmittance enhances from 60% to 70% (500 nm) and the haze decreases from 30% to 10% respectively, which may be correlated with the changes in the grain size of the LIFTO. Performance of the DSSCs with the LIFTO substrates having a haze value of ca. 25% shows the best photocurrent and solar cell conversion efficiency. [ABSTRACT FROM AUTHOR]

Highlights: [•] Ionic liquids (ILs) were modified and used in dye-sensitized solar cells (DSSCs). [•] Various carbon derivatives were added in the IL electrolytes. [•] Carbon derivatives provided the additional pathway for charge transportation. [•] Efficient quasi-solid-state DSSCs were achieved by using CYC-B6S dye. [ABSTRACT FROM AUTHOR]

An improved light-harvesting ruthenium dye with an alkyl bithiophene group, designated as CYC-B1, is employed as the photosensitizer for a zinc oxide (ZnO)-based dye-sensitized solar cell (DSSC). ZnO films with N3 and CYC-B1 dyes exhibit different surface appearances. Interestingly, the ZnO nanocrystal electrode surface with CYC-B1 dye is found to be almost free from Zn2+/dye-agglomerations, usually observed in the case of other commercial ruthenium dyes for such an electrode surface, e.g., N3 dye. Owing to this favorable effect of the CYC-B1 dye, the DSSC with a ZnO film (designated as ZN20) sensitized with this dye exhibited an average efficiency (η) of 4.85 ± 0.03%, which is about 94% higher than the η of the cell with N3 dye (2.50 ± 0.12%). The enhancements of the cell with CYC-B1 dye are explained by analyzing the electrochemical impedance spectra (EIS) and laser-induced photocurrent transients. Further, polymethylmethacrylate (PMMA) spheres with uniform sizes of ca. 300 nm are synthesized and incorporated to template the ZN20 film (designated as PMMA-ZN20); this PMMA-ZN20 film is used as the scattering layer and it is coated on the underlayer ZN20 film to make the photoanode film (ZN20/PMMA-ZN20) of a DSSC. The thus fabricated DSSC shows an η of 5.40 ± 0.03%. [ABSTRACT FROM AUTHOR]

Abstract: An efficient back-illuminated dye-sensitized solar cell (DSSC) is made with a flexible Ti-foil based photoanode composed of a composite TiO2 film with TiO2 nanotubes (TNT) and TiO2 nanoparticles (TNP). The composite TiO2 film is fabricated through a novel dipping–rinsing–hydrolysis (DRH) process by inserting TiO2 into TNT and sintering the product to form TNP inside TNT. By directly placing TiO2 nanoparticles into TNT, the former grow internally from the base of TNT to occupy it completely. This solves previous problems of incomplete filling of TNP into TNT, which used partial penetration of TiCl4 reactant from the top of the TNT. In the present case, the TNP are grown from the base of TNT. A DSSC containing TNT and TNP prepared in this way shows a photoelectric efficiency of 6.45%, which is much higher than that (4.21%) of a DSSC with untreated TNT. The films are characterized by using scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. The improvement in the photoelectric efficiency is explained by using electrochemical impedance spectroscopy (EIS), incident photon-to-current conversion efficiency (IPCE) analysis, and UV-absorption spectra analysis. [Copyright &y& Elsevier]

Abstract: Highly ordered TiO2 nanotubes (TNT) stamps were synthesized on Ti foils by anodization and ultrasonic vibration techniques to enhance the Ti foil active surface area. A dye-sensitized solar cell (DSSC) with the as-prepared Ti foil coated by Pt as the counter electrode (CE) shows a cell efficiency (η) of 9.62% owing to the excellent electrocatalytic ability for its CE. With the replacement of a conducting plastic as the photoanode substrate, a η of 3.12% is obtained for an all flexible DSSC. [Copyright &y& Elsevier]