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Abstract: ZnO porous thin films with nanowire structure were deposited by the one-step electrochemical deposition method. And a CdS layer was coated on the as-deposited ZnO nanowire thin films by successive ionic layer adsorption and reaction (SILAR) method to passivate surface states. Then the films were further sensitized by CdSe quantum dots (QDs) to serve as a photoanode for fabricating quantum dots-sensitized solar cells (QDSSCs). The effect of the CdS interfacial passivation layer on the performance of the QDSSCs was systematically investigated by varying the SILAR cycle number and heating the passivation layer. The amorphous CdS layer with an optimized thickness can effectively suppress the recombination of the injected electrons with holes on QDs and the redox electrolyte. The newly formed CdS layer on the surface of the ZnO nanowire thin film obviously prolongs the electron lifetime in the passivated ZnO nanoporous thin film because of the lower surface trap density in the ZnO nanowires after CdS deposition, which is favorable to the higher short-circuit photocurrent density (J sc). For the CdSe QDs-sensitized ZnO nanoporous thin film with the interfacial passivation layer, the J sc and conversion efficiency can reach a maximum of 8.36mAcm−2 and 2.36%, respectively. The conversion efficiency was improved by 83.47% compared with that of the cell based on the CdSe QDs-sensitized ZnO nanoporous thin film without CdS interfacial passivation (0.39%). [Copyright &y& Elsevier]

Abstract: A novel thixotropic composite electrolyte was fabricated by using the amine group-functionalized silica nanoparticles as the gelator of an ionic liquid-based electrolyte for dye-sensitized solar cells. The SEM image of electrode deposited with electrolyte confirms that the high viscous gel electrolyte has a good contact with TiO2 electrode ascribed to the thixotropic property of the electrolyte. Based on the thixotropic and ionic liquid based-electrolyte containing the amine group-functionalized silica particles, the cells show better performance owing to the increased open-circuit voltage than that of the liquid device, yield a high energy conversion efficiency of 6.69% under AM 1.5 illumination at 100mVcm−2 when the content of the amine group-functionalized silica is 15wt.% and exhibit a long-term stability without sealing. [Copyright &y& Elsevier]

Abstract: A new kind of carboxyl group-functionalized silica nanoparticles were synthesized and employed as framework to form “soggy sand” electrolyte for dye-sensitized solar cells. The property of this electrolyte has been evaluated by studying the effect of the carboxyl group-functionalized silica nanoparticles content on the performance of dye-sensitized solar cells. The cells based on electrolyte containing the carboxyl group-functionalized silica nanoparticles show better performance owing to the increased short-circuit photocurrent than that of the liquid device and yield the energy conversion efficiency of 7.1% under AM 1.5 illumination at 100mVcm−2 when the content of the carboxyl group-functionalized silica is 15wt.%. [Copyright &y& Elsevier]

Abstract: We prepared highly ordered titanium dioxide nanotube arrays (TNAs) by anodizing Ti foils in F− containing electrolyte. The thickness and dye loading amount of TNAs were 26μm and 1.06×10−7 molcm−2, respectively. TiO2 nanoparticles (TNPs) were electrophoretically deposited on the inner wall of nanotube to produce coated nanotube arrays (TNAP). The dye loading was increased to 1.56×10−7 molcm−2, and the electron transport rate improved. TNAs and TNAP were sensitized with ruthenium dye N3 to yield dye-sensitized TiO2 nanotube solar cells. The power conversion efficiency of TNA-based dye-sensitized solar cells (DSSCs) was 4.28%, whereas the efficiency of TNAP-based DSSCs increased to 6.28% when illuminated from the counter electrode. The increase of power conversion efficiency of TNAP-based DSSCs is ascribed to the increased surface area of TNAs and the faster electron transport rate. [Copyright &y& Elsevier]

A TiO 2 compact layer was coated on fluorine-doped tin oxide (FTO) glass substrate prior to deposition of SnO 2 nanocrystalline thin film to suppress backflow of electrons from FTO to the SnO 2 nanocrystalline thin film. The resultant thin film was used as a photoelectrode to fabricate dye-sensitized solar cell. For comparison, a SnO 2 compact layer was also prepared to discuss the effect of the TiO 2 compact layer on the electron backflow process. Compared with the dye-sensitized SnO 2 nanocrystalline thin film solar cell without the compact layer, light-to-electric conversion efficiency for the solar cell with the TiO 2 compact layer was improved by 82.1% and it was even improved by 41.7% compared with the cell with the SnO 2 compact layer. Electrochemical impedance spectroscopy and open-circuit voltage decay of dye-sensitized solar cells were measured to demonstrate the improvement mechanism due to the TiO 2 compact layer. Both recombination resistance at the photoelectrode/electrolyte interface and lifetime of electrons on the SnO 2 nanocrystalline thin film were increased due to introduction of the TiO 2 compact layer. Because the conduction band of TiO 2 is higher than that of SnO 2 , the TiO 2 compact layer acts as not only a physical barrier to separate FTO substrate from electrolyte, thus suppressing recombination of electrons on FTO with the electrolyte, but also a potential barrier to effectively block the backflow of electrons from FTO substrate to the SnO 2 thin film. [ABSTRACT FROM AUTHOR]

We prepared highly-ordered titanium dioxide nanotube arrays (TNAs) by anodizing Ti foils in F-containing electrolytes. The crystalline nature and morphology of the TNAs were studied using X-ray diffraction patterns and scanning electron microscopy. We found the morphology of TNAs affects the light-to-electricity conversion efficiency ( η) of dye-sensitized solar cells (DSSCs). The efficiency of DSSCs reached 5.95% under the condition of light illuminated from the counter electrode. The high efficiency of TNA-based DSSCs was attributed to the neat top surface of TNAs, which allows more dye molecule loading on the surface of the TiO nanotubes, and fewer electron recombination centers and a low interface resistance of integrated TNAs. [ABSTRACT FROM AUTHOR]

Abstract: Pt counter electrodes (CEs) with different platinum loading have been prepared using chemical reduced method on flexible indium-doped tin oxide coated polyethylene naphthalate (ITO-PEN) for dye-sensitized solar cells (DSSCs). H2PtCl6·6H2O terpineol solutions were screen printed on the transparent ITO-PEN substrates. After drying, H2PtCl6 was reduced by treating it in NaBH4 solution followed by the hydrothermal treatment at 100°C. The obtained Pt CEs with different Pt-loading (2.4–7.7μg/cm2) were characterized by SEM, XPS, electrochemical impedance and transmission spectrum measurement. The Pt CEs show high catalytic activity, low charge transfer resistance (0.26–1.38Ωcm2) and good light transmittance (about 70% at 400–800nm). The light-to-electricity conversion efficiency of the flexible DSSC fabricated with the prepared Pt CE and the TiO2 photoanode prepared on Ti substrate by screen printing technique attains 5.41% under the simulated AM 1.5 sunlight, which is almost same as that based on the thermal decomposited Pt CE on FTO-glass. Compared with other methods to prepare Pt CEs, chemical reduced method is simple and suitable for flexible polymer substrates and the large scale preparation of DSSCs. [Copyright &y& Elsevier]

Compression and incorporated graphene significantly improve light transmittances and charge transport properties of an opaque and poor internal-connected mesoporous photoanode, as well as improve the PCE of the corresponding device. Semi-transparent TiO 2 /graphene photoanodes are prepared at room temperature via an electrophoretic deposition method followed by compression and applied in dye-sensitized solar cells (DSSCs). Compression enhances the power conversion efficiency (PCE) of a DSSC, which constitutes up 18.4 times improvement compared to the uncompressed device. Incorporating graphene into the compressed film further improves the PCE by 28.8%. Simultaneously, compressing and graphene incorporating can greatly increase the film's transmittance at long wavelengths, benefiting to the use of DSSCs as front unit in tandem solar cells. Scanning electron microscopy, porosity measurements, electrochemical impedance spectroscopy and open circuit voltage decay are performed to investigate the mechanisms. It is demonstrated that compressing a film can reduce the porosity and improve the inter-particle connections, which accounts for the increased light transmittance and enhanced PCE. The incorporated graphene can provide extra charge carrier pathway due to its excellent charge transport properties, as well as protect TiO 2 nanostructure by preventing film cracking upon pressing due to its good flexibility, thus increases PCE to 6.75%, which, to our best knowledge, is the highest value among DSSCs with room-temperature prepared photoanodes. [ABSTRACT FROM AUTHOR]

Vacuum ultraviolet (VUV) light with a wavelength of 172 nm has the capacity to convert the oxygen contained metal organic precursor into metal oxide. Here, zinc acetate precursor thin film is directly converted into ZnO thin film by the irradiation of 172 nm VUV light rather than the high temperature sintering. The converting processes were demonstrated by the measurements of FTIR, XRD, SEM and XPS. And then the effect of irradiating time on the morphology, thickness and transparence of the prepared ZnO thin films was discussed. The ZnO thin film was further used as the compact layer in the photoelectrode of dye-sensitized solar cell (DSSC) to suppress the recombination processes of photogenerated electrons on the conducting glass electrode. For the different irradiation times, the photoelectric conversion efficiency of DSSC based on the compact layer prepared by the irradiation for 30 min is the highest reaching 10.27%, which is also higher than that of DSSCs without the compact layer and even with the compact layer prepared by the high temperature sintering. The uniform, dense, pinhole-free and amorphous ZnO thin film on the conducting glass substrate can be successfully prepared using the VUV irradiation technology for the compact layer of DSSCs. The ZnO compact layer prepared by the VUV light of 172 nm from zinc acetate precursor thin film shows better performance than the sintered layer for the photoelectrode of dye-sensitized solar cell. [Display omitted] • ZnO compact thin film is prepared by 172 nm VUV irradiation from zinc acetate. • ZnO thin film is used as a compact layer in photoelectrode of DSSCs. • The compact layer prepared by VUV irradiation is better than the sintered layer. [ABSTRACT FROM AUTHOR]

Abstract: 1-Oligo(ethylene oxide)-3-methylimidazolium iodide (PEOMImI) was synthesized and applied to dye-sensitized solar cells (DSSCs) by blending it with different 1-alkyl-3-methylimidazolium iodides used as ionic liquid electrolytes. The 1-propyl-3-methylimidazolium iodide (PMII) blend enabled the DSSC to attain a higher solar energy conversion efficiency of 4.52% under a light intensity of 100mWcm−2. The addition of N-methylimidazole (NMBI) to the electrolytes increased the conversion efficiency as compared to DSSCs based on NMBI-free electrolytes. The addition of both 1-allyl-3-methylimidazolium iodide (AMII) and NMBI enabled DSSCs to reach their highest solar energy conversion efficiency of 6.14% under a light intensity of 100mWcm−2. The ionic conductivity and diffusion coefficient of the triiodide were found to be augmented dramatically after adding NMBI, which leads to an increase in the photocurrent density. The enhancement mechanism of NMBI in the electrolyte was investigated by Raman spectroscopy and differential scanning calorimetry, and it was mainly due to the enhancement of electron exchange in electrolytes. [Copyright &y& Elsevier]

Abstract: Poly(vinylpyridine-co-ethylene glycol methyl ether methacrylate) (P(VP-co-MEOMA)) and α,ω-diiodo poly(ethylene oxide-co-propylene oxide) (I[(EO)0.8-co-(PO)0.2] y I) were synthesized and used as chemically cross-linked precursors of the electrolyte for dye-sensitized solar cells. Meanwhile, α-iodo poly(ethylene oxide-co-propylene oxide) methyl ether (CH3O[(EO)0.8-co-(PO)0.2] x I) was synthesized and added into the electrolyte as an internal plasticizer. Novel polymer electrolyte resulting from chemically cross-linked precursors was obtained by the quaterisation at 90°C for 30min. The characteristics for this kind of electrolyte were investigated by means of ionic conductivity, thermogravimetric and photocurrent–voltage. The ambient ionic conductivity was significantly enhanced to 2.3×10−4 Scm−1 after introducing plasticizer, modified-ionic liquid. The weight loss of the solid state electrolyte at 200°C was 1.8%, and its decomposition temperature was 287°C. Solid state dye-sensitized solar cell based on chemically cross-linked electrolyte presented an overall conversion efficiency of 2.35% under AM1.5 irradiation (100mWcm−2). The as-fabricated device maintained 88% of its initial performance at room temperature even without sealing for 30 days, showing a good stability. [Copyright &y& Elsevier]

Abstract: A poly(ether urethane) (PEUR)/poly(ethylene oxide) (PEO)/SiO2 based nanocomposite polymer is prepared and employed in the construction of high efficiency all-solid-state dye-sensitized nanocrystalline solar cells. The introduction of low-molecular weight PEUR prepolymer into PEO electrolyte has greatly enhance the electrolyte performance by both improving the interfacial contact properties of electrode/electrolyte and decreasing the PEO crystallization, which were confirmed by XRD and SEM characteristics. The effects of polymer composition, nano SiO2 content on the ionic conductivity and I3 − ions diffusion of polymer-blend electrolyte are investigated. The optimized composition yields an energy conversion efficiency of 3.71% under irradiation by white light (100mWcm−2). [Copyright &y& Elsevier]

Abstract: Nanocrystalline TiO2 films were prepared on flexible Ti-metal sheets by electrophoretic deposition followed by chemical treatment with tetra-n-butyl titanate (TBT) and sintering at 450°C. X-ray diffraction (XRD) analysis indicates that TBT treatment led to the formation of additional anatase TiO2, which plays an important role in improving the interconnection between TiO2 particles, as well as the adherence of the film to the substrate, and in modifying the surface properties of the nanocrystalline particles. The effect of TBT treatment on the electron transport in the nanocrystalline films was studied by intensity-modulated photocurrent spectroscopy (IMPS). An increase in the conversion efficiency was obtained for the dye-sensitized solar cells with TBT-treated nanocrystalline TiO2 films. The cell performance was further optimized by designing nanocrystalline TiO2 films with a double-layer structure composed of a light-scattering layer and a transparent layer. The light-scattering effect of the double-layer nanocrystalline films was evaluated by diffuse reflectance spectra. Employing the double-layer nanocrystalline films as the photoelectrodes resulted in a significant improvement in the incident photo-to-current conversion efficiency of the corresponding cells due to enhanced solar absorption by light scattering. A high conversion efficiency of 6.33% was measured under illumination with 100mWcm−2 (AM 1.5) simulated sunlight. [Copyright &y& Elsevier]

A new kind of polythiophene derivative, Poly(3-(2-[4-(2-ethylhexyloxy)-phenyl]-vinyl)-2,2'-bithiophene) (PTh), was applied in dye-sensitized solar cell to extend the light response of nanocrystalline TiO2 electrode. UV-vis absorption and fluorescence spectra were employed to investigate the interaction of PTh with nanocrystalline TiO2. The absorption coefficient of the PTh was high in visible part of spec- trum, and the fluorescence emission of the PTh can be efficiently quenched by TiO2 nanoparticles owing to charge injection from the excited singlet state of PTh to the conduction band of the TiO2 particles. Cyclic voltammetry measurements were performed to study the dye regeneration reaction at the nanocrystalline TiO2/electrolyte interface. The solar cell sensitized with PTh exhibited a short-circuit photocurrent (Isc) of 3.08 mA/cm², an open circuit voltage (Voc) of 511 mV and an overall efficiency of 0.9% under the illumination of 100 mW/cm² (AM 1.5). [ABSTRACT FROM AUTHOR]

Quaternary Cu 2 ZnSnS 4 (CZTS) nanocrystalline thin films were in situ grown on FTO coated conductive glass by a low cost solvothermal method. The effect of the reaction time and the concentration of precursor solution on the purity and morphologies of the deposited thin films was studied. The morphology, crystal structure and composition of the deposited thin films were characterized by scanning electron microscope, high resolution transmission electron microscope, X-ray diffraction, Raman spectroscopy and energy-dispersive X-ray spectroscopy. The pure wurtzite CZTS nanoparticles can be formed as the reaction time is 20 h. The film prepared at the optimized precursor solution concentration has uniform thickness, smooth surface and tight binding between the nanoparticles. The performance of the deposited CZTS thin films used as the counter electrode for dye-sensitized solar cells (DSSCs) was evaluated by measuring photocurrent density-voltage curves of DSSCs, electrochemical impedance spectroscopies and Tafel polarization curves of the symmetric cells. Photoelectric conversion efficiency of DSSC based on the optimized CZTS counter electrode reached 6.19%. The excellent photoelectric performance is attributed to the better surface morphology and conductive skeleton of the prepared CZTS thin film. The in situ solvothermal preparation method of the CZTS thin films for counter electrode of DSSCs is green, low cost and simple. Cu 2 ZnSnS 4 thin film in situ deposited on FTO substrate by a low cost solvothermal method has good microstructure and catalytic activity to the iodide reduction to be used as a high efficient counter electrode of dye-sensitized solar cells. Image 1 • Cu 2 ZnSnS 4 thin film is in situ deposited on FTO substrate by a low cost solvothermal method. • Cu 2 ZnSnS 4 film is well adhered to the substrate to greatly reduce the inactivation interface. • As CE of dye-sensitized solar cells, Cu 2 ZnSnS 4 film has equivalent catalytic activity to Pt. [ABSTRACT FROM AUTHOR]

BaTiO 3 is used to fabricate the electron transport layer of perovskite solar cells due to its spontaneous polarization. Li+ ions were doped into BaTiO 3 by the hydrothermal synthesis to increase the spontaneous polarization. The particle size of the as-prepared BaTiO 3 nanoparticles becomes smaller and more uniform for doping of Li+ ions with a molar ratio of 1.0 during the synthesis processes. The absorption edge shifts towards the short wavelength with the increase in the doping amount. Further, TiO 2 nanocrystalline thin film was deposited on the Li-doped BaTiO 3 thin film, the double layer was used as an electron transport layer of perovskite solar cell to indirectly demonstrate the effect of doping on the spontaneous polarization of BaTiO 3. The perovskite solar cell based on BaTiO 3 with 1.0 doping molar ratio of Li+ ions shows the highest light-to-electric conversion efficiency of 14.3% accompanying with the highest short-circuit photocurrent density. The measurements of impedance spectra and intensity modulating photocurrent spectra indicate that the photocurrent enhancement of perovskite solar cells is attributed to the spontaneous polarization enhancement of Li-doped BaTiO 3 thin films. The enhanced internal electric field in the BaTiO 3 thin layer accelerates the photogenerated electron transport in the electron transport layer of perovskite solar cell. Image 1 • The Li+ doping affects spontaneous polarization on BaTiO 3. • The spontaneous polarization in Li-doped BaTiO 3 promotes the electron transport. • Li-doped BaTiO 3 in electron transport layer improves performance of perovskite solar cell. [ABSTRACT FROM AUTHOR]

Nanocomposite polymer electrolytes containing poly(ether urethane) (PEUR)/poly(ethylene oxide) (PEO)/modified SiO2were prepared for all-solid-state dye-sensitized solar cells with a high efficiency of 4.86% and an active area of 0.25 cm2under AM1.5 conditions at 100 mW cm−2irradiation. [ABSTRACT FROM AUTHOR]