Study Of Cu₂ZnSn (S_xSe_1-x)₄ Thin Film Solar Cells Prepared By Nanoparticles Method And Their Extended Application

With the rapid development of society, the global energy demands are increasing in high speed. However, the main sources of global energy are fossil fuels so far, which belong to non-renewable energy resource, and the usage of fossil fuels will release toxic gases and greenhouse gases. And hence it is very necessary to exploit the new energy resources, in which the solar energy is enormous and environment-friendly and can be utilized by photovoltaic power generation system. The traditional photovoltaic power generation industry depends on crystalline silicon solar cells, but the relatively expensive cost restricts the application of solar cells. The research of low-cost photovoltaic materials can reduce the production cost of solar cells to facilitate the development of solar cell industry. Cu2ZnSn(SxSe1-x)4(CZTSSe) is a kind of Ⅰ2-Ⅱ-Ⅳ-Ⅵ4 P type semiconductor materials with direct bandgap of 0.9-1.5 eV that can be adjust by controlling the ratio of S/Se, high absorption coefficient of 104-105 cm-1 and abundant resources, which can be a kind of promising candidate for the low-cost thin film solar cells. Cu2ZnSnS4(CZTS) nano-particles are fabricated by hot-injection method in this study and the effect of annealing condition on Cu2ZnSn(SxSe1-x)4 solar cell performance has been researched systematically. And, some exploratory work based on nano-particle method has also been carried out. The specific content of this dissertation is as follows:Firstly, the Cu2ZnSnS4 nano-particles, with uniform size distribution, high purity and good crystallinity and dispersion, were obtained by using hot-injection method with the reaction time of 30min after the investigation of different conditions. The synthesized Cu2ZnSnS4 nanocrystals have the average grain size of 20nm and the bandgap of 1.5eV. Then, the Cu2ZnSnS4 nano-particles were dissolved into 1-Hexylmercaptan with the concentration of 200mg/ml to form ink as the precursor for subsequent spin. The synthesized precursor film were annealed under different conditions systemically to research the properties of synthesized Cu2ZnSn(SxSe1-x)4 film and the performance of solar cells correspondingly. The results show that the Cu2ZnSn(SxSe1-x)4 films obtained by direct selenization appear stratification phenomenon damaging the final device performance. While the Cu2ZnSn(SxSe1-x)4 films obtained by sulfidation-selenization process have little stratification phenomenon. Finally, the solar device with selenization process has the best efficiency of 3.5% with the annealing condition of Se550℃-30min and the solar cell with the optimized sulfidation-selenization process has the best efficiency of 4.5% with the anneal condition of S600℃-20min and then Se550℃-60min.In the second part, the exploratory research based on nano-particles method has been conducted. Cu2ZnSnS4 nano-particles synthesized by hot-injection method were applied in the perovskite solar cells as a kind of new and low-cost hole transport materials. The perovskite solar cell obtained the best device efficiency of 12.75% that is similar with the result of using spiro-OMeTAD as hole transport material on the condition of using the Cu2ZnSnS4 nanoparticles with 30 min reaction time, spinning speed of 4000 rpm and annealing at 100℃ for 10 min.In addition, one of difficulties in the field of solar cell research is fabrication of the battery device having large area. In order to solve the problem of uneven thickness using spin coating method in the preparation of large area precursor film, the fabrication of Cu2ZnSn(SxSe1-x)4 thin film solar cells using doctor blade process was studied and the final device with the efficiency of 2.95% was obtained.