Dye-sensitized solar cells with PVA–KI–EC–PC gel electrolytes

Gel polymer electrolytes consisting of PVA–EC–PC–KI have been studied in this work. The highest room temperature (298 K) conductivity of 12.92 mS cm −1 is obtained for PVA-based gel polymer electrolyte (GPE) with composition 14.5 PVA-21.7 EC-28.7 PC-30.4 KI-4.7  I 2 (in wt%). The high conductivity is due to the highest number density of mobile ions in the electrolyte. The conductivity–temperature dependence follows the Vogel–Tamman–Fulcher (VTF) relationship. The trend of pseudoactivation energy (Ea) with salt concentration is contrary to that of conductivity. PVA-based GPEs with 5 to 35 wt% KI were used as a medium in ruthenium 535 (N719) dye-sensitized solar cells. The efficiency ( η ) of the solar cells increased as the composition of KI salt in the electrolyte increased. The highest power conversion efficiency of 2.74 % is obtained for solar cells fabricated with electrolyte containing 35 wt% KI. The variation of efficiency follows the same trend as short circuit current density (Jsc) . The increase in Jsc is influenced by the increase in iodide ion concentration in the electrolyte that assists the redox process and helps electron to shuttle between ionized dye and counter electrode

Gel polymer electrolyte based on LiBOB and PAN for the application in dye-sensitized solar cells

Dye-sensitized solar cells (DSSCs) have been fabricated using metal complex N3 dye coupled with LiBOB and PAN-based gel polymer electrolyte (GPE). Conductivity of the GPE at room temperature was 1.2 x 10(-2) S cm(-1). The deconvoluted vibration spectra at different temperatures between 1000 and 970 cm(-1) show the existence of ion pairs and free ions. Overall efficiency and fill factor of the DSSC with LiBOB-BMII-PAN-I-2 GPE system is 0.65% and 48% respectively. The cell with LiBOB-BMII-PAN-I-2 GPE system appears to be stable under varied light intensity attributed to the presence of redox couple mediator in the GPE. Impedance measurements show that the DSSC with LiBOB-BMII-PAN-I-2 GPE has longer electron lifetime which suggests a lower electron recombination rate

Computational studies on linear, second and third-order nonlinear optical properties of novel styrylquinolinium dyes

The electric dipole moments (μ), static dipole polarizabilities (α) and first hyperpolarizabilities (β) of styrylquinolinium dyes, D8 and D21, have been computed by density functional theory (DFT). The one-photon absorption (OPA) characterizations have been investigated using UV–vis spectroscopy and further interpreted using computational chemistry. The time-dependent Hartree–Fock (TDHF) method has been used to describe the dynamic dipole polarizabilities, dynamic second-order and also static and dynamic third-order nonlinear optical (NLO) properties. D8–D21 have rather high β and second hyperpolarizabilities (γ). The highest occupied molecular orbitals (HOMO), the lowest unoccupied molecular orbitals (LUMO) and the HOMO–LUMO band gaps for D8–D21 have been evaluated by DFT

Impact of annealing process on stacking orientations and second order nonlinear optical properties of metallophthalocyanine thin films and nanostructures

Abstract The paper presents the second order nonlinear optical properties of Cu, Co, Mg and Zn metallophtalocyanines thin films. The films were fabricated by physical vapor deposition in high vacuum onto fused silica glass substrates. In order to investigate both optical and structural properties an annealing process in an ambient atmosphere for 12 h at temperatures equal to either 150 °C or 250 °C applied after the fabrication process. Atomic force microscopy images were obtained for an observation of the structural property changes. The thickness of the thin films was in the range from 80 nm to 120 nm. The size and shape of the forming nanostructures were different for different metallophthalocyanines and depended on the phase of the material. As-deposited sample of copper phthalocyanine formed the smallest nanostructures – standing columns with 100 nm of the height and 40 nm of the diameter. Annealed sample formed the largest nanostructures – lying cuboids with dimensions: 10 × 1000 × 40 nm. The second harmonic generation measurements have been carried out in order to investigate the second order nonlinear optical properties and their dependence on the structure of the thin films after the annealing process. Moreover the fittings based on the two models have been carried out in order to understand deeper the origin of the experimental findings. It was found that the annealing process can significantly modify both the structural and the second order nonlinear optical properties of the metallophthalocyanine thin films

Second-order Nonlinearities of Anionic 3-dicyanomethylen-5,5-dimethyle-1-[2-(4-hydroxyphenyl)ethenyl)]-cyclohexene

Due to the connecting one π-conjugated group with the two backside donor and acceptor groups, anionic 3-dicyanomethylen-5,5-dimethyle-1-[2-(4-hydroxyphenyl)ethenyl)]-cyclohexene (1) might possess nonlinear optical (NLO) properties. To estimate the potential for second-order NLO behaviour; the electric dipole moments and dispersion-free dipole polarizabilities and first hyperpolarizabilities have been determined by density functional theory (DFT) at B3LYP/6-31++G(d, p) level. Quantum mechanical calculations using time-dependent Hartree-Fock (TDHF) procedure have been utilized to evaluate frequency-dependent second-order nonlinearities of 1. The one-photon absorption (OPA) characterization of 1 has been theoretically obtained by means of configuration interaction (CI) with 6-31G basis set. Our theoretical results on the maximum OPA wavelength, second-order susceptibilities and corresponding microscopic NLO responses are accorded with the previous experimental observations of the investigated compound. The highest occupied molecular orbitals, the lowest unoccupied molecular orbitals and the HOMO-LUMO band gaps for 1 have been also examined by DFT/B3LYP method