Research On Morphology Control Of Electrodeposited ZnO And Its Heterojunction Assembly With CZTS

With the ever-decreasing fossil energy sources,copper zinc tin sulfur(CZTS)solar cell has received extensive attention as an energy conversion device.Multilayer structure of CZTS solar cell currently is soda lime glass/molybdenum/CZTS/cadmium sulfide/intrinsic zinc oxide/aluminum doped zinc oxide/aluminum,which is complicated,and most functional layers need to be prepared by vacuum.The method not only has high cost but also needs complicated equipment and processes.Therefore,the use of low-cost methods for the assembly of solar cell is of great significance.In this thesis,ZnO nanoarrays with seed layer and without seed layer,ZnO nanotubes,and ZnO thin film were prepared by electrodeposition.The morphologies of ZnO are controlled by adjusting the deposition potential,composition and pH of the deposition solution,temperature and deposition time.The results showed that negative shift in the deposition potential increases the diameter of the zinc oxide nanoarrays.Decreasing the pH of the deposition solution can destroy the zinc oxide seed layer,so that the diameter of the zinc oxide nanoarrays was rapidly increased and the edge of the zinc oxide nanorods were partically dissolved.Promoting the temperature of the deposition solution facilitated the conversion of the zinc oxide from the thin film to the arrays and improves its crystallinity.Changing the deposition time effectively adjusted the thickness and diameter of the zinc oxide nanoarrays.The optimum deposition conditions for the zinc oxide nanoarrays are determined:the deposition solution is 2 mM zinc nitrate and 0.1 M potassium chloride,deposition potential is-1.0 V(vs.SCE),deposition solution pH value is 6.5,and deposition temperature is 70?.In this thesis,ZnO nanoarrays without seed layer,ZnO film and ZnO nanotubes were prepared by electrodeposition method,and the morphologies of ZnO thin film were controlled under different electrodeposition conditions.Pure phase CZTS absorber layer was prepared by electrodeposition and sol-gel method.CZTS/ZnO heterojunction with different morphologies were successfully prepared on CZTS substrate by electrodeposition The zinc oxide film can cover the surface of the CZTS uniformly and continuously,forming a good contact.Clusters of zinc oxide nanoarrays distributed on the surface of CZTS thin film.ZnO nanoarrays/CZTS heterojunction were prepared by electrodeposition of CZTS thin film on electrodeposited ZnO nanoarrays by adding CdS buffer layer to overcome the difficulty of ZnO corrosion caused by the deposition solution.ZnO nanoarrays/CZTS heterojunction were formed on CZTS thin film by sol-gel method on electrodeposited ZnO nanoarrays.Through the adjustment of the CZTS assembly process,the coarse structure of the initial ZnO nanoarrays is preserved,and ZnO nanoarrays/CZTS heterojunction structure was obtained.This structure effectively increased the contact area between the window layer and the absorber layer,which was beneficial to the carrier transport and provided a new way of solar cell assembly.The assembly of ZnO with different morphologies and CZTS is realized by the use of electrodeposition and sol-gel methods with low-cost and simple equipment,providing a variety of assembly method choices for improving the performance of ZnO/CZTS solar cell.