表面In掺杂TiO2的N719/TiO2-Inx%/FTO薄膜电极的光电转换效率

采用溶胶-凝胶法制备出In 表面修饰的TiO₂ (TiO₂-Inx%)纳米粒子, x%代表在In 掺杂的TiO₂样品中In³⁺与In³⁺和Ti⁴⁺离子摩尔百分含量. 利用二(四丁基铵)顺式-双(异硫氰基)双(2,2''-联吡啶-4,4''-二羧酸)钌(II)(N719)作为敏化剂, 制备出N719/TiO₂/FTO (氟掺杂锡氧化物)和N719/TiO₂-Inx%/FTO染料敏化薄膜电极. 光电转换效率实验表明, 在薄膜电极+0.5 mol·L^-1 LiI+0.05 mol·L^-1 I₂的三甲氧基丙腈(MPN)溶液+Pt 光电池体系中,N719/TiO₂-Inx%/FTO薄膜电极的光电转换效率均高于N719/TiO₂/FTO, 其中N719/TiO₂-In0.1%/FTO的光电转换效率比N719/TiO₂/FTO提高了20%. 利用X 射线衍射(XRD)、X 射线光电子能谱(XPS)、漫反射吸收光谱(DRS)、荧光(PL)光谱和表面光电流作用谱确定了TiO₂-Inx%样品中In3+离子的存在方式和能带结构; 利用表面光电流作用谱研究了N719/TiO₂-Inx%/FTO薄膜电极的光致界面电荷转移过程. 结果表明, In3+离子在TiO₂表面形成O-In-Cl_n (n=1, 2)物种, 该物种的表面态能级位于导带下0.3 eV处; 在光电流产生过程中, O-In-Cl_n (n=1, 2)表面态能级有效地抑制了光生载流子在TiO₂-Inx%层的复合, 促进了阳极光电流的增加, 从而导致N719/TiO₂-Inx%/FTO薄膜电极的光电转化效率高于N719/TiO₂/FTO, 并进一步讨论了光致界面电荷转移的机理.

Photoelectric Conversion Efficiency of N719/TiO2-Inx%/FTO Film Electrodes Incorporating In Doped at the TiO2 Surface

Nanoparticles of TiO₂ with surface modification by In doping were prepared using a sol-gel technique. These materials had the general formula TiO₂-Inx%, where x represents the mole percent of In3+ ions in the combined In³⁺ and Ti⁴⁺ metal ion content. N719/TiO₂/FTO (fluorine doped tin oxide) and N719/ TiO₂-Inx%/FTO film electrodes were prepared, using N719 dye as a sensitizing agent. These thin film electrodes were incorporated into solar cells composed of 0.5 mol·L^-1 LiI, 0.05 mol·L^-1 I₂, methoxypropionitrile (MPN) and Pt. It was determined that the photoelectric conversion efficiencies of the N719/TiO₂-Inx%/FTO film electrodes were higher than that of N719/TiO₂/FTO. In particular, the conversion efficiency of N719/TiO₂-In0.1%/FTO was 20% greater than that of N719/TiO₂/FTO. The band structure and In³⁺ ion content of TiO₂-Inx% samples were analyzed using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and optical diffuse-reflection spectroscopy (DRS), as well as by examination of photoluminescence (PL) and surface photocurrent action spectra. The photo-induced charge transfer processes of the N719/TiO₂-Inx%/FTO film electrodes were also elucidated using surface photocurrent action spectra. The results showed that O-In-Cl_n (where n=1 or 2) species were formed at the TiO₂ surface, with surface state energy levels 0.3 eV below the conduction band of TiO₂. The surface state energy levels of these species effectively inhibit the recombination of photo-generated carriers during the photocurrent generation process, and also serve to increase the anodic photocurrent and significantly improve the photoelectric conversion efficiency of N719/TiO₂-Inx%/FTO thin film electrodes. This work also discusses the interfacial light-induced charge transfer mechanisms in these materials.