TiO 2 nanocrystalline porous anodic film synthesis and optical properties of the photoelectric conversion
|School||Central South University|
|Keywords||Dye-sensitized solar cells(DSSCs) TiO2 hydrothermal sol-gel compact layer poly(ethylene glycol)|
Dye-sensitized solar cells（DSSCs） are a kind of new type solar cells. Because of its low cost, simple fabrication technology, high photoelectric conversion efficiency, DSSCs have become a hot research spot in the world.In this paper, TiO2 nanocrystallines were prepared by hydrothermal method and the TiO2 compact layers were synthesized by sol-gel method, then the TiO2 nanoporous anodes were fabricated using the synthesized TiO2 nanocrystallines. The preparation anodes were used to assemble dye-sensitized solar cells. The crystal structure of the TiO2 nanocrystalline was detected by X-ray diffraction（XRD）, while the surface morphology, thickness and optical absorption performance of the film were characterized by scanning electron microscopy （SEM）, profile measuring system and UV-vis spectrophotometer （UV-vis） respectively. The photoelectric properties of the solar cells were also studied by simulated sunlight and voltammetric curve scanning method. The influence of crystal structure, surface morphology, thickness and the compact layer on the photoelectric efficiency were studied.TiO2 nanocrystallines were prepared by hydrothermal reaction using tetrabutly titanate as the raw material and PEG（MW=600,2000） as the additive. It was found that the growth of anatase nanocrystallines was inhibited and the growth of rutile nanocrystallines was facilitated by adding PEG. When the amount of PEG2000 is about 5%, the best photo-to-electric energy conversion efficiency of 2.86%is reached using liquid state electrolyte without 4-tert-pyridine. But when the amount of PEG600 is about 10%, it began appearing rutile phase, the best photovoltaic performance is 1%, and photo-to-electric energy conversion efficiency is 1.85%. The photoelectric properties were improved by adding moderate PEG.The influence of film thickness on the photoelectric efficiency was studied. The optical absorption rate increased rapidly first then changed slowly with the increasing of TiO2 film thickness. When the thickness of film increased, the open-circuit voltage and short-circuit current density first increased, then decreased; the fill factor declined continuously. The photo-to-electric efficiency also first increased, then decreased. The best film thickness is 10.12μm in the experiments. Thus, for the anode with particular nanocrystalline structure, there exists an optical film thickness.Add compact layer between nanocrystalline porous film and conductive glass substrate using sol-gel method. The adding of compact layer can rise open-circuit voltage and fill factor of DSSCs, but the fill factor decreased with the increasing of the thickness of dense film. The photovoltaic performance is best when using 0.15mol/L sol as the compact layer, and we obtained the best photoelectric energy conversion efficiency 3.21%at AM 1.5（100 mW/cm2） illumination when the thickness of the film is 3 layers.