Shen Heping, Lin Hong, Zhao Lin, Liu Yizhu, Oron Dan
Department of Material Science and Engineering, Tsinghua University, Beijing 100084, China.
J Nanosci Nanotechnol. 2013 Feb;13(2):1095-100. doi: 10.1166/jnn.2013.5974.
While holding great potential as sunlight absorbers, quantum dots (QDs), which are generally much larger than dye molecule in size, which makes it more difficult to deposit them on the surface of TiO2. As a result, relatively low QD loading is now one of the most challenging issues for improving the photovoltaic performance of QD-sensitized solar cells (QDSSC). In this study, TiO2 photoanodes with different pore sizes and porosities were constructed by systematically varying the solid content of the TiO2 paste. It was confirmed that reducing the solid content resulted in both larger pore sizes and higher porosities. CdS quantum dots were then deposited on these different electrodes by the successive ionic layer adsorption and reaction (SILAR) method, with either 4 or 7 repetitive cycles. By correlating the photovoltaic performances of QDSSCs with different solid contents of TiO2 paste and number of SILAR cycles of CdS QD deposition, it was found that the combination of 7 SILAR cycles with 10% electrode solid content yielded the highest overall energy conversion efficiency. In particular this cell exhibited an outstanding open-circuit photovoltage up to 640 mV using a polysulfide electrolyte, which currently ranks the highest among reported literature. This outcome is due to the fact that a 10%-solid-content provided the largest pore sizes and the highest porosity for the QDs deposition, while the 7 SILAR cycles guaranteed the sufficient CdS QD loading which is favorable for light harvesting.
量子点（QDs）作为太阳光吸收剂具有巨大潜力，但其尺寸通常比染料分子大得多，这使得将它们沉积在TiO2表面更加困难。因此，相对较低的量子点负载量是目前提高量子点敏化太阳能电池（QDSSC）光伏性能最具挑战性的问题之一。在本研究中，通过系统地改变TiO2浆料的固含量，构建了具有不同孔径和孔隙率的TiO2光阳极。证实降低固含量会导致更大的孔径和更高的孔隙率。然后通过连续离子层吸附和反应（SILAR）方法，以4次或7次重复循环将CdS量子点沉积在这些不同的电极上。通过将不同TiO2浆料固含量和CdS量子点沉积SILAR循环次数的QDSSC的光伏性能相关联，发现7次SILAR循环与10%电极固含量的组合产生了最高的总能量转换效率。特别是，使用多硫化物电解质时，这种电池表现出高达640 mV的出色开路光电压，这在目前报道的文献中排名最高。这一结果是由于10%的固含量为量子点沉积提供了最大的孔径和最高的孔隙率，而7次SILAR循环保证了足够的CdS量子点负载量，有利于光捕获。
