【作者】 付亚楠；

【导师】 靳正国；

【作者基本信息】 天津大学 ， 材料学， 2009， 博士

【摘要】 纳米晶TiO₂多孔薄膜作为重要的半导体材料,其光电化学性质研究已得到人们的广泛关注,在太阳能转换、光电子器件及光催化等方面具有重要的应用。本文采用浸渍-提拉和原位蒸发两种方法进行了PS胶晶阵列的自组装制备。通过提拉法制备PS微球胶晶时,发现升高乳液温度可以促进动态提拉下阵列的有序生长。而且适当温度时,提高乳液中PS球的体积分数可使阵列层数和有序度得到提高并抑制阵列中断裂线的产生。原位蒸发的胶晶组装是多核过程,经历了四方排列到密堆积的转变。当通过降低压强加速蒸发时,自组装更加稳定,可以在较宽压强范围内得到有序胶晶。以Ti（OBu）4为原料,P123为模板剂,HCl为水解抑制剂制备了前驱体溶胶,通过浸渍-提拉制膜后,450℃热处理3h得到介孔结构的锐钛矿相纳米晶TiO₂薄膜,晶粒尺寸¹0nm。样品的BET比表面积和总孔体积分别为89.6m2/g和0.18cm3/g,平均孔径5.7nm。通过改变水解抑制剂,研究了介孔TiO₂的微结构特征。结果表明,在HCl或AcAc-HCl双抑制剂的作用下,样品的比表面积和孔隙率较大,分别为176.3m2/g,139.2m2/g和60%,57%,证实HCl对钛源具有较强的水解抑制作用,可形成钛低聚物小团簇,从而有利于其和PEO基团的键合,形成较有序的介孔结构TiO₂。采用PS胶晶/P123双模板,通过浸渍-提拉/溶胶-凝胶法成膜,450℃热处理后制备了有序大孔-介孔锐钛矿TiO₂薄膜,晶粒尺寸7.4nm,光学带隙3.00eV。浸渍-提拉法灌注PS模板时,有序大孔结构的形成明显依赖于溶胶浓度。较低浓度的溶胶对PS润湿性差,导致灌注孔壁不完整。当浓度为0.13-0.15M时,大的表面张力和较小的润湿角有利于溶胶灌注,大孔结构有序度高。当浓度继续升高时,溶胶流动性变差,不利于其在PS上的铺展而导致结构有序度降低。对介孔TiO₂进行金属元素Nb、Sb、Ge、Zn和Sn的掺杂,并考察其作为染料敏化太阳电池（DSSCs）n-电极的光伏性能。结果表明,与未掺杂介孔TiO₂相比,Ge掺杂阳极的电池开路电压升高;Nb和Sb的施主掺杂有利于TiO₂阳极中的电子传输,使短路电流增大;Sb掺杂薄膜具有较大的比表面积,有利于提高光吸收率。Ge掺杂TiO₂的DSSC光电转换效率最大,为2.95%。更多还原

【Abstract】 Porous nanocrystalline TiO₂ （nc-TiO₂） film is an important semiconductor material. Recently, its photoelectrochemical properties have attracted much attention for research works, which are desired for many applications, such as solar energy converters, optoelectronic devices and photocatalysts.In this paper, two methods （dip-drawing and in-situ solvent evaporation） were employed for preparing PS colloidal crystal array. In self-assembly of PS colloidal crystal by dip-drawing method, the elevated emulsion temperature could promote ordered arrangement of PS spheres during the dynamic drawing process. At proper temperature, the array thickness and orderliness can be enhanced by increasing the PS volume fraction of emulsion, meanwhile which obviously reduced the fracture lines in array. In in-situ evaporation process for preparing PS colloidal crystal, self-assembly behaves a multi-nucleus site evolution, and undergoes the transformation from square to close packing arrangement. Technique of decreasing atmospheric pressure was adopted for accelerating evaporation so as for a more stable arrangement and wider range of pressure for ordered colloidal crystal.The mesoporous TiO₂ precusor sol was prepared using tetrabutyl orthotitanate （Ti（OBu）4） as titanium source, P123 as template and HCl as hydrolysis inhibitor. With film fabrication by dip-drawing and then calcining at 450℃for 3h, mesoporous anatase nc-TiO₂ film was obtained with grain size of ¹0nm. The Brunauer-Emmett-Teller surface area （SBET）, total pore volume and average mesoporous size is 89.6m2/g, 0.18cm3/g and 5.7nm, respectively. Through using different hydrolysis inhibitors, the microstructure of mesoporous TiO₂ was researched. Results show that under effect of inhibitor HCl or acetylacetone-HCl, higher SBET and porosity of 176.3m2/g, 139.2m2/g and 60%, 57% respectively, were obtained. Because the additive HCl possesses strong inhibiting effect for hydrolysis, which results in small size of Ti oligomers that favors connection with PEO moieties for formation of more ordered mesoporous structure of TiO₂ film.Using PS colloidal crystal/P123 as bitemplate through dip-drawing/sol-gel for film fabrication, ordered macro-mesoporous anatase TiO₂ film was prepared after calcining at 450℃, with grain size of 7.4 nm and band gap of 3.00eV. The perfection of inverse opal structure mainly depends on the precursor sol concentration. Under low sol concentrations, worse wetting ability of sol to PS spheres led to incomplete TiO₂ inorganic wall. In concentration range of 0.13-0.15M, more ordered macroprous structure were fabricated, resulting from big surface tension and small contact angle that both favor the permeation of sol into PS template. Along with increase of sol concentration, fluidity of sol could not match the spread in gaps among PS spheres well, leading to worse orderliness of macroporous structure.Mesoporous nc-TiO₂ films were doped by metal element of Nb、Sb、Ge、Zn and Sn, and its photovoltaic performance was studied as n-electrode of dye-sensitized solar cells （DSSCs）. The results show that when using Ge doped TiO₂ film as anode, open-circuit photovoltage of DSSC increases comparing with pure TiO₂. The short-circuit photocurrent of DSSCs based on Nb or Sb doped anode rise, since Nb and Sb are both donor for Ti that favors transfer of electron received from dye in the TiO₂ electrode. Larger SBET of Sb doped TiO₂ film raises the light absorptivity. And Ge doped DSSC possesses the highest conversion efficiency of 2.95%.更多还原