纳米晶二氧化钛光声与表面光伏特性

Photoacoustic and Surface Photovoltaic Characters of Nanocrystalline TiO_2

利用溶胶-凝胶法制备二氧化钛纳米晶粉末.结合光声和表面光伏技术对样品表面态性质和光诱导电荷输运特性进行研究.结果表明,纳米晶TiO_2样品在波长为380nm处出现的表面光伏响应与锐钛矿型TiO_2的表面电子结构有关,属于带-带电荷转移跃迁;随着样品粒径的减小,在2.38eV能级处形成一个具有明显受体特征的表面电子态;依据样品光声效应和表面光伏效应之间的能量互补关系发现,尽管随着样品平均粒径的减小无辐射跃迁产生的光声信号增强,但是适当提高样品中金红石的相对含量,可以显著减少样品表面无辐射跃迁的成分,提高光量子效率.

Nanocrystalline TiO2 was synthesized by sol-gel method. The surface state properties and transport characters of photogenic free charge carders were probed by the combination of photoacoustic and surface photovoltaic techniques. The results showed that the surface photovoltage （SPV） response appearing at 380 nm of the samples was closely related to the surface electron structure of anatase-type TiO2 nanoparticles, which belonged to a band-band transition; and that the shoulder peak appearing at 470 nm was related to the surface states of TiO2 nanoparticles, which was a sub-band-gap charge transfer （CT） transition, and had an obvious donor character. By the energy complementarity between photoacoustic and surface photovoltaic effects of the samples, it was experimentally proved that the nonradiative transitions were responsible for the increasing intensity of photoacoustic signals with decreasing average particle size of the sample; but the number of the nonradiative transitions could be dramatically decreased by a little increase of anatase content in the sample, resulting in increasing quantum-optical efficiency.