Design and characterization of alkoxy-wrapped push-pull porphyrins for dye-sensitized solar cells

Three alkoxy-wrapped push-pull porphyrins were designed and synthesized for dye-sensitized solar cell (DSSC) applications. Spectral, electrochemical, photovoltaic and electrochemical impedance spectroscopy properties of these porphyrin sensitizers were well investigated to provide evidence for the molecular design

Raman and Mössbauer spectroscopic studies of tungsten doped Ni–Zn nano ferrite

In this study, tungsten substituted Ni-Zn nano ferrites of the composition Ni0.5Zn0.5WxFe2−xO4 with x = 0.0, 0.2, 0.4 have been synthesized by a co-precipitation method. The prepared samples were pre-sintered at 850 °C and then annealed at 1000 °C for 3 h each. The structural, morphological, optical and magnetic properties of these samples were studied by using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy (RS) and Mössbauer spectroscopy (MS). XRD revealed the formation of spinel single-phase structure with an average crystallite size of 53–60 nm. Fourier transform infrared spectroscopy show two prominent peaks primarily due to the tetrahedral and octahedral stretching vibrations in the range of 400–600 cm−1. Raman spectra indicate first order three Raman active modes; (A1 g + Eg + T2 g) at around 688, 475 and 326 cm−1. Mössbauer spectroscopy reveals that substitution of W3+ for Fe3+ cation results in reduction of total magnetic moment and consequently the net magnetization

Porphyrin Dyes with High Injection and Low Recombination for Highly Efficient Mesoscopic Dye-Sensitized Solar Cells

The photovoltaic performance and charge recombination characteristics of porphyrin-based dye-sensitized solar cell (DSC) devices have been investigated using the impedance spectroscopy (IS) technique. The IS results provide key information related to the device performance for a highly efficient porphyrin dye (YD2), a reference porphyrin dye (YD0), and a commercial ruthenium dye (N719). The DSC devices constructed using YD2 and N719 dyes reach similar internal power conversion efficiencies (7.41% vs 7.54%) due to the higher injection of the YD2 dye that is compromised by a lower photovoltage. In addition, both YD2 and N719 dyes exhibit the same charge-transfer resistance, indicating that the recombination rates of both dyes are very similar. The diarylamino group plays a key role to repel the triiodide ions from the titania surface so that the charge recombination of YD2 is less significant compared with that of YD0

Functions of Self-Assembled Ultrafine TiO2Nanocrystals for High Efficient Dye-Sensitized Solar Cells

In this paper, we demonstrate a simple approach of self-assembled process to form a very smooth and compacted TiO2 underlayer film from ultrafine titanium oxide (TiO2) nanocrystals with dimension of 4 nm for improving the electrical properties and device performances of dye-sensitized solar cells (DSSCs). Because the TiO2 film self-assembles by simply casting the TiO2 on fluorine-doped tin oxide (FTO) substrate, it can save a lot of materials in the process. As compared with control DSSC without the self-assembled TiO2 (SA-TiO2) layer, short-circuit current density (Jsc) improves from 14.9 mA/cm(2) for control DSSC to 17.3 mA/cm(2) for masked DSSC with the SA-TiO2 layer. With the very smooth SA-TiO2 layer, the power conversion efficiency is enhanced from 8.22% (control) to 9.35% for the DSSCs with mask and from 9.79% (control) to 11.87% for the DSSCs without mask. To explain the improvement, we have studied the optical properties, morphology, and workfunction of the SA-TiO2 layer on FTO substrate as well as the impedance spectrum of DSSCs. Importantly, we find that the SA-TiO2 layers have better morphology, uniformity, and contact with FTO electrode, increased workfunction and optical transmission, as well as reduced charge recombination at the contact of FTO substrate contributing to the improved device performances. Consequently, our results show that the simple self-assembly of TiO2 ultrafine nanocrystals forms a very good electron extraction layer with both improved optical and electrical properties for enhancing performances of DSSCs