The TiO2 thin film layers were introduced with the spin-coating method between FTO electrode and TiO2 photoanode in dye sensitized solar cell (DSSC) to prevent electron back migration from the FTO electrode to electrolyte. The DSSC containg different thickness of TiO2 thin film (10-30, 40-60 and 120-150 nm) were prepared and photovoltaic performances were analysed with /-Vcurves and electrochemical impedance spectroscopy. The maximum cell performance was observed in DSSC with 10-30 nm of TiO2 thin film thickness (11.92 mA/cm2, 0.74 V, 64%, and 5.62%) to compare with that of pristine DSSC (11.09 mA/cm2, 0.65 V, 62%, and 4.43%). The variation of photoelectric conversion efficiency of the DSSCs with different TiO2 thin film thickness was discussed with the analysis of crystallographic and microstructural properties of TiO2 thin films.
The performance of the quasi-solid state DSSC composed of long wavelength absorbing squaraine dye was investigated and compared with that of ruthenium-complex (N3) sensitized DSSC. In spite of the narrow sensitizing region of SQ dye from 500 nm to 750 nm, the quasi-solid state DSSCs gave a moderate solar energy-to-electricity conversion efficiency under AM 1.5 G irradiation (100 mW/cm2) of 2.34%, a short-circuit current density of 5.56 mA/cm2, with an open-circuit voltage of 650 mV.
Abstract DSSCs based on quasi-solid type of electrolytes were prepared to investigate the influence of ionic mobility and recombination kinetics in electrolytes on DSSC performances. The improved ionic mobility of electrolyte in PMMA system resulted in the enhancement of Jsc value in DSSC which was well confirmed with the incident photon-to-current spectra and the impedance analysis. Furthermore, the retarded recombination rate from TiO2 electrode to electrolyte in PMMA system enhanced the electron life time of DSSC in the photoanode. DSSCs based on quasi-solid type of electrolytes composed of PMMA showed a power conversion efficiency of 3.36% underAM 1.5 illumination (100 mWcm−2) in an photo active area of 0.24 cm2, short circuit current density of 7.69 mAcm−2, open circuit photo voltage of 0.69 Vandafill-factor of 64%. Keywords: Dye-sensitized solar cellsionic mobility of electrolytephotovoltaic performancesPMMA and PEO electrolytequasi-solid type of DSSC Acknowledgment This research was financially supported by the Ministry of Education, Science Technology (MEST) and Korea Industrial Technology Foundation (KOTEF) through the Human Resource Training Project for Regional Innovation. Notes a R1 is FTO Interface resistance. b R2 is due to the resistance at the interface between the counter electrode and the electrolyte. c R3 is possibly originated from the backward charge transfer from TiO2 to the electrolyte and the electron conduction in porous TiO2 film. d τis life time of an electron in DSSC. J. H. Kim and K.-S. Ahn contributed equally to this work as the corresponding authors.
Nitrogen-doped TiO2 crystallites were prepared via the hydrolysis of TiCl4 using an ammonia medium in an aqueous solution for DSSC photoelectrodes. The optimized photoelectrode for the DSSC was prepared with 9.4 nm sized N-doped TiO2 crystal (BET; 200 m2/g), which provides a relatively high short circuit current and energy conversion efficiency in the DSSC. The photovoltaic performance of the N-doped TiO2 electrode was confirmed using incident photon-to-current efficient spectra, impedance analyses, and Bode-phase plots which proved that the N-doped TiO2 electrode has a significantly enhanced electron lifetime compared with that of the P25 electrode.
The demonstrated Först-type resonance energy transfer (FRET) is demonstrated in quasi-solid type dye-sensitized solar cells between organic fluorescence materials as an energy donor doped in polymeric gel electrolyte and a ruthenium complex as an energy acceptor on the surface of TiO2. Strong spectral overlap of emission/absorption of the energy donor and acceptor is required to obtain high FRET efficiency. The judicious choice of the energy donor allows the enhancement of the light harvesting characters of the energy acceptor (N3) in quasi-solid dye sensitized solar cells which increases the power conversion efficiency by 25% compare to that of a pristine cell. The optimized cell architecture fabricated with the quasi-solid type electrolyte containing fluorescence materials shows a maximum efficiency of 5.08% with a short-circuit current density (J(sc)) of 12.63 mA/cm2, and an open-circuit voltage (V(oc)) of 0.70 V under illumination of simulated solar light (AM 1.5, 100 mW/cm2).
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