Utilization of Anatase Nanocrystalline Titania from Titania Nanotubes as An Electrode Material in Dye-sensitized Solar Cells

【摘要】：正An efficient dye-sensitized solar cells(DSSCs),involving the use of anatase nanocrystalline TiO_2 on transparent conductive oxide(TCO) layers as photoanode,a platinized TCO as counter electrode,and the electrolyte,has been extensively considered to be a promising method to convert sunlight into electricity.The preparation method of TiO_2 significantly affects the photocurrent-voltage characteristics due to the change in surface area,crystallinity and grain size of TiO_2.In this study,mesoporous TiO_2 with pure anatase phase (AMP-TiO_2) was obtained as following described:TiO_2 powders(Degussa P25) were immersed in concentrated NaOH_((aq)) in an autoclave at 130℃for 24 hr,followed by further treatment with dipping in 0.05 mol/L HNO_3 at 80℃for 24 hr.The resulting material was mesoporous anatase TiO_2 with small crystal size (d_A) of 7.7 nm and 186 m~2/g of surface area as evidenced by XRD and N_2 adsorption isotherm at 77 K.The photoelectrodes with different film thickness were prepared by coating AMP-TiO_2 onto the fluorine-doped tin oxides(FTO) with doctor-blade method followed by sintering at 450℃for 0.5 h.The photoelectrodes were placed in 0.3 mmol/L N-719/EtOH solution for 24 h.Pt-coated FTO was used for the counter electrode.The electrolyte solution was 0.5 mol/L lithium iodide,0.05 mol/L iodine.Dye sensitization of AMP-TiO_2 has been investigated by measuring photocurrent in an electrochemical cell under 1.5 AM illumination(100 raW/cm~2). Dependence of short-circuit photocurrent density(I_(sc)) on the thickness of AMP-TiO_2,P25 and sol-gel TiO_2(d_A = 10.4 nm and S_(BET)=118 m~2/g) were investigated.I_(sc) of the cells made from AMP-TiO_2 was higher than that of P25 by 130%and that of sol-gel TiO_2 by 60%at the optimal film thickness.Moreover,they also exhibit higher conversion efficiency(η) with improved I_(sc) and open-circuit voltage(V_(oc)).The enhancement is believed to be attributed to the higher surface area and smaller crystal size.Highestηof 8.01%with I_(sc) of 17.4 mA/cm~2, V_(oc) of 0.76 V and fill factor of 0.61 is observed when the film thickness is ca.13μm.