Research On Quantum Dots Modified Mesoporous Perovskite Solar Cells

As an important renewable energy, solar photovoltaic generation is being more and more popular and researchable. There has been such a perovskite solar cell whose efficiency development is extremely fast. Its photoelectric conversion efficiency is a key parameter to measure the battery's performance. In this paper, the structure of the cell is: FTO conductive glass/compact TiO2/mesoporous TiO2/perovskite layer/hole transport layer/Au. Product TiO2 and ZnO quantum dots film on the mesoporous TiO2 layer, respectively. Make modification to the surface of mesoporous structure to improve the device's photovoltaic performance.In the paper, we synthesized TiO2 quantum dots with solvo-thermal, Zn O quantum dots with sol-gel. And the two kind of quantum dots all have a size of about 5 nm. In fabrication of the cell device, we adjusted concentration of the quantum dots' s solution to change the surface morphology of mesoporous layer, adjusted spin speed to change the thickness of mesoporous structure. All the work was to study their effects on the photoelectric conversion efficiency of the device.The main conclusions are as follows: the battery without quantum dots can reach a maximum efficiency of 9.693% when its mesoporous layer have a thickness of 661 nm. The battery modified by ZnO quantum dots can improve the photoelectric conversion efficiency significantly. When the density of ZnO quantum dots is 1 mg/mL, the efficiency reached to 11.440%. However, the highest efficiency of the battery modified by TiO2 quantum dots is only 7.714 percent. Even lower than the battery without quantum dots. The results of microstructure test show that, the modification quantum dots on the surface of mesoporous is obvious. What's more, lower concentrations did not change the mesoporous layer's thickness. When add a suitable concentration of quantum dots to the battery, the surface area of the mesoporous structure will increase. And this will make contribution to the separation and injection of electron-hole pairs. At the same time, by testing the energy band of quantum dots, we found that the conduction band of ZnO quantum dots and the TiO2 dense layer were very close. It's beneficial to transport electrons. So, the addition of ZnO quantum dots can improve the photoelectric conversion efficiency of the battery. But to TiO2 quantum dots, its conduction band is lower than both the photovoltaic layer and the TiO2 dense layer. It will lead to the formation of a potential well which can hinder the transport of electrons. Therefore, although the TiO2 quantum dots modified the mesoporous to an increased specific surface area, it still caused a decrease in photoelectric conversion efficiency.