Mg2+离子掺杂增强TiO2:Yb3+/Tm3+纳米晶上转换发光性能

Enhancing the up-conversion luminescence properties of TiO2：Yb3+/Tm3+ compositions by Mg2+ ion doping

摘要:

染料敏化太阳能电池因其大规模生产、低成本、环保和潜在的灵活性而受到广泛的研究兴趣，作为光阳极的TiO2半导体纳米材料在吸收有机染料分子方面起着关键作用．然而，有机染料（如N3和N719）只能吸收可见太阳光，这限制了太阳能电池的光谱响应范围，降低了电池的光电效率．为了解决这一问题，利用稀土离子上转换技术将近红外光转换为可以被有机染料吸收的可见光．采用水热法制备金属Mg2+离子掺杂TiO2:Yb3+/Tm3+纳米晶，对Mg2+离子掺杂增强TiO2:Yb3+/Tm3+纳米晶上转换发光性能及机理进行了研究．研究结果表明：Mg2+离子的掺杂不改变TiO2:Yb3+/Tm3+锐钛矿晶体结构，其形貌仍保持薄片状；Mg2+离子通过修饰Tm3+离子周围局部环境，增强了上转换蓝光和红光发光强度，从而扩大了太阳光谱响应对近红外波段的吸收和利用．功率曲线和上转换布局机制研究结果表明，上转换蓝光是通过双光子布局，而Mg2+离子掺杂则使上转换红光由双光子转变为单光子布局．

Abstract:

Dye-sensitized solar cells （DSSCs） have received extensive research interest due to their mass production， low cost， environmentally friendly and potential flexibility. TiO2 semiconductor nanomaterials used as photoanodes play a key role in absorbing organic dye molecules. However， organic dyes， such as N3 and N719， can only absorb visible sunlight， which limits the spectral response range of solar cells and reduces the photoelectric conversion efficiency. To solve this problem， rare-earth ions upconversion technology is used to convert near-infrared light into visible light that can be absorbed by organic dyes. In this work， TiO2：Yb3+/Tm3+ nanocrystals doped with Mg2+ ions were synthesized by hydrothermal method， and the optical characteristics and upconversion mechanism of TiO2：Yb3+/Tm3+/Mg2+ were studied. The experimental results show that doping Mg2+ ions remained the crystal structure of anatase TiO2：Yb3+/Tm3+ with the similar morphology of thin sheet. By modifying the local environment around Tm3+ ion， Mg2+ ions enhanced the intensities of blue and red luminescence， leading to an increased absorption and utilization of solar spectral response. Power curve and upconversion mechanism indicated that blue upconversion emission was populated by a two-photon process， while the red upconversion one was populated by one-photon process due to doping Mg2+ ions.