CdS/CdSe/TiO_2多级空心微球光阳极中量子点覆盖度的提高

Abstract

TiO_2多级空心微球(THHSs)具有高的比表面积、强的光散射效应以及良好的电子传输性质,以此作为光阳极材料,可以显著提升CdS/CdSe敏化太阳能电池(QDSSCs)的性能。但基于化学浴沉积方法获得的这一类电池中量子点在光阳极表面的覆盖度通常不高(50%左右),本文发展了一种基于表面选择性吸附原理的多步沉积方法,选取特定分子(正十二硫醇)限制已有量子点的生长,通过二次沉积成功提高了CdS/CdSe在TiO_2多级空壳微球表面的覆盖度。使用此方法最终得到高达85.4%的覆盖度。结果表明,量子点覆盖度的增加有效提高了电池对太阳光的利用率,使得光电流获得了明显的增加。同时,二氧化钛空白表面积的减小还可以抑制电子和空穴的复合。优化后的电池光电流密度为15.69 mA?cm~(-2),填充因子为0.583,电压为0.605 V,最高光电转换效率为5.30%。

TiO2 hierarchical hollow spheres (THHSs) are considered an ideal material for photoanodes of CdS/CdSe quantum dot-sensitized solar cells (QDSSCs) because of their high specific surface area, strong light scattering effect, and excellent charge transfer capability. However, in a typical CdS/CdSe quantum dot deposition process, chemical bath deposition, the coverage of the CdS/CdSe quantum dots is relatively low (-50%). According to the different surface properties of CdS/CdSe quantum dots and TiO2, we have developed a novel route to increase the quantum dot coverage while preventing their aggregation. In our method, 1dodecanethiol was used as a surface protection molecule on the quantum dots. Then, in the secondary chemical bath deposition process, the newly emerged quantum dots grew' only on the TiO2 surface and thus the coverage notably increased. Eventually, the quantum dot coverage reached 85.4%. This method effectively enhanced light utilization and led to an increase in the photocurrent of the QDSSCs. The reduced blank surface of TiO2 also efficiently suppressed electron-hole recombination. Thus, the photocurrent density was 15.69 mA" cm-2, the fill factor was 0.583, and the voltage was 0.605 V. As a result, a power conversion efficiency of 5.30% was obtained.