【作者】 孙盼盼；

【导师】 张昕彤；

【作者基本信息】 东北师范大学 ， 材料物理与化学， 2013， 博士

【摘要】 一维TiO₂纳米结构因其优异的光生电荷分离与输运性质和卓越的化学稳定性在太阳能转换与利用领域受到广泛关注。特别是TiO₂单晶纳米线阵列的制备与光电转换应用是近年来国内外研究的热点。本文以染料/半导体敏化TiO₂纳米线太阳能电池为研究对象，从TiO₂纳米线的可控制备、纳米线-纳米粒子复合结构增强光吸收和电荷分离、无序空腔散射层增强光利用、和构造半导体敏化固态电池等方面开展研究，探索利用TiO₂纳米线阵列实现高效率太阳能光电转换的途径。具体研究概述如下：以钛酸纳米片作为晶种层，在SnO₂:F （FTO）导电玻璃等多种衬底表面实现TiO₂纳米线阵列的水热法制备，解决了TiO₂纳米线的生长对衬底的依赖性问题。研究表明，钛酸纳米片晶种层的引入能够抑制纳米线在FTO上生长过程中的簇集，显著增大纳米线阵列的粗糙度；另一方面纳米片层还能够覆盖裸露的FTO电极，作为阻挡层抑制I3-电解质在FTO表面的还原。以N719染料敏化纳米线阵列制备敏化太阳能电池，在AM1.5模拟太阳光下，采用纳米片晶种层的TiO₂纳米线阵列相比直接生长在FTO表面的纳米线阵列制备的电池在短路电流、开路电压和填充因子等方面均有提高，总体太阳能光电转换效率提高约3.4倍。为提高纳米线电极的光捕获效率，进一步制备了TiO₂金红石纳米线和锐钛矿纳米粒子复合结构。以1.4微米厚度的纳米线/纳米粒子复合结构作为光阳极，制备染料敏化太阳能电池器件。在AM1.5G模拟太阳光激发下，器件的光电转换效率达到3.8%，分别是纳米线器件的2.2倍，和纳米粒子器件的1.5倍。稳态/瞬态吸收光谱和开路光电压衰减动力学研究表明，金红石纳米线和锐钛矿纳米粒子在光电转换过程中发挥着协同促进作用：一方面纳米粒子的引入提高了复合结构的光捕获效率，另一方面金红石-锐钛矿异质结能够抑制TiO₂/电解液界面和TiO₂/N719界面的电荷复合，从而提高光生电子的收集效率。为提高TiO₂金红石纳米线和锐钛矿纳米粒子复合结构的光捕获效率，进一步在纳米线复合结构上构造具有无序空腔（空腔尺寸为200nm或450nm）结构的TiO₂纳米粒子散射层。在AM1.5G模拟太阳光激发下，染料敏化太阳能电池光电转换效率从2.62%提高到3.47%（200nm空腔）和4.07%（450nm空腔）。透过/反射光谱表征以及光电流活性谱研究表明，多孔薄膜中的空腔结构是有效的光散射中心，特别是在580-700nm波长范围内散射效果明显，从而提高了染料分子对入射光的利用效率，显著提高器件的短路光电流和光电转换效率。为克服染料单分子层光吸收能力不足和使用液体电解质带来的器件不稳定性问题，以Sb2S3直接带隙半导体为敏化层，p-型CuI为空穴导体，制备了TiO₂纳米线/Sb2S3/CuI/Au全固态半导体敏化太阳能电池。在AM1.5G模拟太阳光激发下，器件光电转换效率达到1.2%。IPCE测试表明器件响应阈值波长为750nm，与Sb2S3带隙一致，峰值效率达到64%，优于染料敏化体系。但是由于固态器件内部严重的界面复合，其暗态电流大大高于染料敏化电池，导致器件的开路电压和填充因子偏低，仅为0.3V和42%，限制其光电转换效率。进一步采用合理的界面工程手段抑制界面复合是提高半导体敏化固态太阳能电池性能的关键。更多还原

【Abstract】 1D TiO₂nanostructures have been extensively studied in solar energy conversionfield, for the excellent photogenerated charge separation and transport properties andgood chemical stability of TiO₂nanostructures. Especially,1D single-crystalline TiO₂nanowire arrays as one of the most potential photoanode materials have attractedimmense scientific research interests, focusing on the preparation and solar energyconversion application of TiO₂nanowire arrays. In this thesis, concentrated on theTiO₂nanowire array based dye/semiconductor-sensitized solar cells, we carried outour research on the controllable synthesis of TiO₂nanowires, facilitatinglight-harvesting and charge separation employing nanowire-nanoparticle compositestructure, enhancing light-harvesting via disordered hollow scattering layer and theall-solid-state semiconductor-sensitized solar cells, searching for approaches inachieving highly efficient TiO₂nanowire based solar cells. Details are listed asfollows:By using titanate nanosheet （TN） film as a seed layer,1D single-crystalline rutileTiO₂nanowire array has been successfully prepared on SnO₂:F （FTO） conductiveglass and other solid substrates via a facile hydrothermal process, solving the problemconcerning the growth dependence of rutile nanowires on the FTO substrate. Detailedstudy revealed that the TN film can suppress the aggragation of nanowires duringgrowth period, thus increasing the dye-loading amount of nanowire arrays; In addition,the TN film can also form a blocking layer which covers the bare FTO surfaceunoccupied by rutile nanowires, suppressing the charge recombination atFTO/electrolyte interface. Under AM1.5G simulated solar irradiation, rutilenanowires grown on a TN film performed better in DSSCs than those on bare FTOconductive glass in terms of all cell parameters including short-circuit current,open-circuit voltage and fill factor, thus giving an improvement of energy conversionefficiency of about3.4times compared with the one without the TN film.In order to enhance the light harvesting efficiency, rutile TiO₂nanowires （NWs）array-anatase nanoparticles （NPs） photoanode system is chosen and fabricated via asimple two-step synthesis process. As an example, a dye-sensitized TiO₂NW-NPcomposite photoanode, only1.4μm thick, exhibits a solar energy conversionefficiency of3.8%under AM1.5G simulated solar irradiation, which is2.2times and 1.5times higher than that of the NW array and NP photoanodes, respectively.Kinetics study in terms of stationary/transient obsorption and open-circuit decaytechnique, demonstrated the synergistic effect of rutile NWs and anatase NPs forphotoelectrochemical solar energy conversion. On one hand, the introduce of anatasenanoparticles improved the light harvesting efficiency of composite structure; On theother hand, the presence of a rutile-anatase heterojunction at the interface reducedcharge recombination at both the NP/electrolyte and NP/dye interfaces, thusimproving the charge collecting efficiency of composite structure.On the purpose of further increasing the light harvesting property of TiO₂NW-NP photoanode, disordered hollow structure （pore size²00nm,450nm） isintroduced as TiO₂nanoparticle scattering layer. Under AM1.5G simulated solarirradiation, energy conversion efficiency of3.47%（pore size²00nm） and4.07%（pore size⁴50nm） are achieved, compared with2.62%of DSSC without the hollowstructure. Optical transmittance and reflectance spectrum and incidentphoton-to-current conversion efficiency study revealed the effective light-scatteringproperties of hollow structures in TiO₂nanoparticle scattering layer, especially overthe wavelength range of580-700nm, thus improved the light harvesting efficiency ofTiO₂NW-NP photoanode. Hence, the photocurrent and overall energy conversionefficiency for the DSSC based on the light-scattering layer is remarkably improved.In order to overcome the inefficient light harvesting problem of monolayereddye-sensitized solar cells, and simultaneously avoiding the solvent leakage andvolatility of liquid electrolyte, all solid-state solar cell device of TiO₂NWs/Sb2S3/CuI/Au was prepared based on the as-synthesized TiO₂NWs, employingdirect bandgap semiconductor Sb2S3as sensitizer, and p-type CuI as hole-transportingmaterial. The device exhibits a solar energy conversion efficiency of1.2%under AM1.5G simulated solar irradiation. The IPCE measurement indicates that thephotocurrent onset is at750nm, which is consistant with the bandgap of Sb2S3, andthe peak efficiency reached64%, which is superior to dye-sensitized cells. But due tothe serious interfacial charge recombination process in solid-statesemiconductor-sensitized solar cells, the dark current of the device is obviously higherthan dye-sensitized solar cells, which lead to lower device open-circuit voltage （0.3V）and fill factor （42%） and finally poor device performance. Therefore, suppressinginterfacial recombination by interfacial engineering is the keypoint for improving theperformance of solid-state semiconductor-sensitized solar cells.更多还原