Solar Cells Based On Silicon And Tin Oxide Nanomaterials

With the increasing urgency on the energy crisis and environmental pollution, the new energy development and utilization are gradually becoming imminent. Among all kinds of new energy, solar energy is undoubtedly the most dazzling star. With its low cost, simple fabrication, cleanliness and better stability, the soalr energy has been attacting more and more attention. In this paper, the material, the structure and the principle of different kinds of solar cells were investigated. Based on the recent progress of solar cells, the fabrication, microstructure, and performance of the solar cells based on the PtRu nanoparticle decorated silicon nanowires, CdS quantum dot sensitized SnO2, and TiO2/SnO2double layers, were systematically studied. The main results of this dissertation are listed as following:1. SiNW was fabricated by wet etching method using HF and AgNO3etching solution. We studied the influence of the concentration of HF acid and AgNO3, etching temperature and time on the morphology of SiNW by changing the experimental parameters.The influence of the different experimental parameters on the morphology of SiNW was tested by using FESEM. The best experimental parameters were obtained for synthesizing the SiNW products with controllable structures:HF concentration4.8M,AgNO3concentration0.02M, etching time60min, temperature50℃. The XRD analysis shows that the silicon crystal structure did not change after etching. The SiNW formation mechanism was analysed in particularly. The study showed that the array is formed mainly due to the oxidation-reduction reaction between the Ag ions and the atoms of Si substrate.2. PtRu nanoparticle decorated SINW was fabricated by one step wet etching method. The PtRu/SiNW sample was prepared by adding H2PtCl6·6H2O and RuCl3·xH2O solution simultaneously to the SiNW wafer pieces in ethylene glycol followed by heating under160℃for1h. The solar cells were composed of PtRu/SiNW, surly film, electrolyte and counter electrode. The solar cells were illustrated with a solar simulator, and photoelectrochemical measurements were conducted using an electrochemical work station. The results show that the PtRuNP-decorated SiNW electrode generates the highest current density and the power conversion efficiency up to7.25%, which is improved to be20.0%higher than that of the PtNP-decorated SiNW electrode, and the efficiency is3times that of the bare SiNW electrode. The main reason for the improved performance is the contact of the metal and the semiconductor that enhances the electronic transmission at the interface as well as reduces the recombination of electrons and holes.3. The hollow structured SnO2nanospheres were synthesized using hydrothermal method. The influence of the concentration of sulphuric acid on the morphology of SnO2was studied. The results show that the SnO2turned into a very uniform hemisphere structure after annealing. The work electrode was fabricated by spin technology. On that basis, CdS quantum dot sensitized SnO2photoelectrode was prepapred by using the successive ionic-layer adsorption and reaction (SILAR) method, then the sensitized SnO2photoelectrode was characterized by FESEM, XRD and TEM. Photovoltaic performance of the sensitized solar cells based on CdS/SnO2electrodes was studied. A maximum5.92mA/cm2short circuit density,0.70V open circuit voltage and3.01%conversion efficiency under one sun illumination was obtanied. Photoelectric conversion efficiency mainly results from the band matching of the CdS quantum dots with SnO2nano-composite materials, which in turn leads to width of light absorption range of the working electrode from the ultraviolet region to the visible light, improving the utilization of sunlight.4. TiO2thin films were first fabricated by using spin coating technology. Then, SnO2film was prepared by using the same method after TiO2thin films annealing. Because the band gap of SnO2and TiO2matches well, and the TiO2layer acts as a butter layer. The J-V curve shows the performance of SnO2TiO2working electrode increased by50%compared to that of the SnO2DSSCs.