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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]

Three unsymmetrical squaraines, where the electron-rich thiophene or bithiophene conjugated fragment was used to link unconventionally the squaraine core and carbazole (or methyl) group, were prepared. JYL-SQ1 with thiophene as a donor and indoline-carboxylic acid as an acceptor has λmax of 568 nm which is much longer than the general metal-free organic dyes. Adding a carbazole unit in JYL-SQ1 (forms JYL-SQ2) can red-shift the λmax to 603 nm. However, cabazole is not a strong donor (and indoline-carboxylic acid is a weak acceptor) the LUMO of all three dyes are delocalized majorly on squaraine unit: the excited electrons of dye molecules injecting into TiO2 are not so efficiency, resulting in low short-circuit current and conversion efficiency. The corresponding DSSC devices have the conversion efficiency of 0.71%, 2.59% and 2.22% for JYL-SQ1, JYL-SQ2 and THL-SQ3, respectively. [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]

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]

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]

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]

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]

Abstract: A nanocomposite thin film, consisting of graphene (GN) and polyaniline (PANI) (designated as GN/PANI) is coated as a catalytic layer on an FTO glass by electro-polymerization from a solution containing aniline (ANI) monomers and GNs; the thus coated electrode is used as a counter electrode (CE) for a dye-sensitized solar cell (DSSC). Modification of the surface of GNs by the ANI monomers is confirmed by thermo-gravimetric analysis (TGA). Fourier transform spectroscopy (FTIR) and UV/Vis absorption spectra are used to demonstrate the non-covalent interactions between ANI and GN in the GN/ANI particles. The effect of the refluxing process on the dispersibility of GN/ANI particles in an aqueous solution is studied. The high electro-catalytic ability of GN/PANI-CE is established through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The short-circuit current density (J SC) and power-conversion efficiency (η) of the DSSC with the GN/PANI-CE are measured to be 16.28 mA cm−2 and 7.17%, respectively, while the corresponding values are 15.01 mA cm−2 and 7.24% for a DSSC with a CE having Pt as the catalytic material (Pt-CE). The composite film of GN/PANI is thus established to be a potential catalyst for replacing the expensive, conventional Pt in a DSSC. [Copyright &y& Elsevier]

Abstract: A novel, heteroleptic ruthenium dye comprising a vinyl group between the carboxylate and bipyridine segments as well as extended π-conjugation of the ancillary ligand, employing alkyl-bithiophene, was synthesized. The dye displayed a remarkably high absorption coefficient of 2.51 × 104 M−1 cm−1 (at 562 nm) for its metal-to-ligand charge transfer band. The photo-to-current conversion efficiency of the corresponding dye-sensitized solar cell was 9.12% under AM 1.5 (100 mW/cm2) irradiation. Furthermore, owing to both the very strong metal-to-ligand charge transfer band and the large number of dye molecules adsorbed on the TiO2 electrode, the conversion efficiency of the dye-sensitized cell was >7.5% at a light intensity ≤198 mW cm−2. [Copyright &y& Elsevier]