| Dye-sensitized solar cell(DSSC) has aroused intensive interest owing to its low cost, great potential and high efficiency. The DSSC consists of photoanode sensitized dye, electrolyte and counter electrode. Photoanode, as a core component, is very important for the photoelectric conversion efficiency. The photoanode modification has also become a hot topic in recent years.In this study, SrAl2O4:Eu downconversion(DC) powders were doped in TiO2 photoanode thin film to improve the photoelectric performance of the DSSC. Three cotents were included: Firstly, TiO2 nanotubes were prepared by anodization method with different anodization time and used as flexible photoanodes in DSSC. The effects of anodization time on photoelectric properties of flexible DSSC were studied. Secondly, SrAl2O4:Eu2+ DC powders were synthesized by citric acid gel method under a reducing atmosphere, and combined with TiO2 nanoparticles(NPs) to prepare the SrAl2O4:Eu2+/TiO2 composite pastes. Then the composite pastes were coated on TiO2 NT photoanode by a screen printing method. Subsequently, unsealed flexible DSSCs were assembled with the sensitized photoanode and the counter electrode. The effects of SrAl2O4:Eu2+ doping content on the photovoltaic performance of the DSSCs were investigated. Thirdly, SrAl2O4:Eu3+ DC powders were synthesized by citric acid gel method under a air atmosphere, and combined with TiO2 NPs to prepare the SrAl2O4:Eu3+/Ti O2 composite pastes. Then the composite pastes were coated on FTO conductive glass by a screen printing method. Subsequently, unsealed rigid DSSCs were assembled with the sensitized photoanode and the counter electrode. Then the effects of DC powders in rigid DSSCs were investigated.The structure and morphology of TiO2 NT were characterized by X-ray diffraction(XRD) and SEM. The structural properties and optical properties of SrAl2O4:Eu2+ phosphors were discussed in terms of XRD and photoluminescence(PL). Differential thermal analysis(DTA), fourier transform infrared spectroscopy(FT-IR), XRD, PL and Brunner-Emmet-Teller(BET) measurements were employed to identify the formation, vibrational stretching frequencies, structural phases, optical properties and BET surface area of SrAl2O4:Eu3+ powders, respectively. The light adsorption properties of the Sr Al2O4:Eu3+/TiO2 composite porous nano-film were examined by ultraviolet-visible(UV-Vis) absorbance spectrometer. The impacts of doping amount on the photovoltaic performance of DSSCs were analyzed by testing battery’s photoelectric properties using sunlight simulator(SS50) and Keithley Source-Meter(Keithley2400). IPCE of SrAl2O4:Eu/TiO2 composite porous nano-film batteries were tested by the SM-25 spectrometer.The experimental results showed that anatase TiO2 was formed after anodizating for 9 h at 500℃.The as-prepared TiO2 nanotube took on compact array and vertical-alignment with internal diameter of 40 nm, external diameter of 80 nm and length of 6.6 μm. The best photoelectric conversion efficiency of the DSSCs was obtained with anodization time of 9h. SrAl2O4:Eu(Eu2+ and Eu3+) powders with perfect crystallization, small grain size and uniform particle size were obtained. The XRD implied that the doped Eu2+ and Eu3+ ions have almost no effect on the SrAl2O4 phase composition. SrAl2O4:Eu2+ and SrAl2O4:Eu3+ powders could be excited by ultraviolet light and effectively convert ultraviolet light to visible light which matched the strong absorbing region of the N719 dye. The IPCE provided more evidence of the DC powders effect. When the ratio of SrAl2O4:Eu2+ in the doping layer was optimized as 1wt%, the photoelectric conversion efficiency of the flexible DSSC reached 3.09%, which was increased by 38.57%, compared with that of the DSSC based TiO2 nanotube photoanode, and increased by 12.36% compared with that of the DSSC with 0% of SrAl2O4:Eu2+. The rigid DSSC based on 3wt% SrAl2O4:Eu3+-doping exhibited the highest photoelectric conversion efficiency of 4.64%, which was 20% higher than that of the DSSC based pure TiO2 photoanode. |
