An Optimized Photoanode Structure for High Efficient CdSe Quantum Dots Sensitized Solar Cells

摘要

An effective photoanode with high light-harvesting ability is necessary for obtaining high efficient quantum dot sensitized solar cells (QDSSCs). In this work, a functionalized gradient structured photoanode was developed and deposited on a transparent conductive glass substrate from bottom to top by a screen-printing process with TiO2 nanoparticles (NPs) and nanorod-microspheres (NMs). A CdSe QDSSC was assembled based on the functionalized gradient film. The QDSSC exhibits an enhanced photoelectric conversion efficiency (PCE) of 4.11%, exceeding that of the cells based on the pure TiO2 NPs, pure NMs and the NPs/NMs homogeneous mixture with equal mass ratios under the same film photoanode thickness by a percentage of 15%, 27% and 14%, respectively. The enhanced photovoltaic performance of the functionalized gradient film-based QDSSC is attributed to the superior light scattering ability of TiO2 NMs in the gradient structure, which is beneficial for light harvesting. Moreover, the incorporation of TiO2 NPs into the voids of the NMs of the gradient photoanode structure will further increase the specific surface area of the photoanode, which also leads to a greater load of quantum dots. Electrochemical impedance spectroscopy analysis further confirmed the differences of electron transport between QDSSCs based on the NPs/NMs gradient film and the cells based on pure NPs, pure NMs and NPs/NMs homogeneous mixture with the same film thickness.