Robb Alex J, Miles Dalton, Salpage Sahan R, Watson Noelle, He Qingquan, Wu Qiang, Hanson Kenneth
Department of Chemistry & Biochemistry, Florida State University, Tallahassee, Florida 32306, United States.
Department of Electrical and Computer Engineering, Florida A&M University-Florida State University College of Engineering, Tallahassee, Florida 32310, United States.
ACS Appl Mater Interfaces. 2020 Aug 26;12(34):38003-38011. doi: 10.1021/acsami.0c07968. Epub 2020 Aug 17.
Metal ion-linked multilayers offer an easily prepared and modular architecture for controlling energy and electron transfer events on nanoparticle, metal oxide films. However, unlike with planar electrodes, the mesoporous nature of the films inherently limits both the thickness of the multilayer and subsequent diffusion through the pores. Here, we systematically investigated the role of TiO nanoparticle film porosity and metal ion-linked multilayer thickness in surface loading, through-pore diffusion, and overall device performance. The TiO porosity was controlled by varying TiO sintering times. Molecular multilayer thickness was controlled through assembling Zn-linked bridging molecules ( = -terphenyl diphosphonic acid) between the metal oxide and the Ru(bpy)((4,4'-POH)bpy)]Cl dye (), thus producing TiO-()- films. Using attenuated total reflectance infrared absorption and UV-vis spectroscopy, we observed that at least two molecular layers (i.e., TiO- or TiO--) could be formed on all films but subsequent loading was dependent on the porosity of the TiO. Rough estimates indicate that in a film with 34 nm average pore diameter, the maximum multilayer film thickness is on the order of 4.6-6 nm, which decreases with decreasing pore size. These films were then incorporated as the photoanodes in dye-sensitized solar cells with cobalt(II/III)tris(4,4'-di--butyl-2,2'-bipyridine) as a redox mediator. In agreement with the surface-loading studies, electrochemical impedance spectroscopy measurements indicate that mediator diffusion is significantly hindered in films with thicker multilayers and less porous TiO. Collectively, these results show that care must be taken to balance multilayer thickness, substrate porosity, and size of the mediator in designing and maximizing the performance of new multilayer energy and electron management architectures.
金属离子连接的多层膜为控制纳米颗粒、金属氧化物薄膜上的能量和电子转移事件提供了一种易于制备且模块化的结构。然而，与平面电极不同，薄膜的介孔性质固有地限制了多层膜的厚度以及随后通过孔隙的扩散。在此，我们系统地研究了TiO纳米颗粒薄膜孔隙率和金属离子连接的多层膜厚度在表面负载、孔内扩散及整体器件性能方面的作用。通过改变TiO烧结时间来控制TiO的孔隙率。通过在金属氧化物与Ru(bpy)₂((4,4'-POH)bpy)]Cl染料（）之间组装锌连接的桥连分子（ = -三联苯二膦酸）来控制分子多层膜的厚度，从而制备出TiO-()-薄膜。利用衰减全反射红外吸收光谱和紫外-可见光谱，我们观察到在所有薄膜上至少可以形成两层分子层（即TiO-或TiO--），但后续负载情况取决于TiO的孔隙率。粗略估计表明，在平均孔径为34 nm的薄膜中，最大多层膜厚度约为4.6 - 6 nm，且随着孔径减小而减小。然后将这些薄膜作为光阳极并入以钴(II/III)三(4,4'-二-丁基-2,2'-联吡啶)作为氧化还原介质的染料敏化太阳能电池中。与表面负载研究结果一致，电化学阻抗谱测量表明，在多层膜较厚且TiO孔隙率较小的薄膜中，介质扩散受到显著阻碍。总体而言，这些结果表明，在设计和最大化新型多层能量和电子管理结构的性能时，必须谨慎平衡多层膜厚度、基底孔隙率和介质大小。
