Preparation Of CZTS Solar Cell’s Buffer And Functional Layer Material

In this thesis, we researched the function and buffer layer of CZTS thin film solar cell. We prepared the CZTS nanoparticle by hot-inject method, made the nanoparticle ink and used this ink to prepare the CZTS nanocrystalline thin films by coating and spin coating. They are annealled in a nitrogen atmosphere at380℃before the vulcanization and selenization. Through the XRD, SEM and other testing test methods, we come to the following conclusions:From TEM, SEM and XRD, nanoparticles’diameter is about7nm-15nm with a high degree of dispersion. Analyzed by EPMA, Zn element suffered a loss during synthesis. From the XRD and Raman spectra,230℃is the best synthesis temperature of the nanoparticles. Annealing can improve the crystallinity, while vulcanization not only increases the crystallinity, but also eliminates Cu4SnS4impurity phase. Selenization can greatly promote the crystallization and impurity phase into CZTS crystal. From SEM, coating and annealing films may crack and spin coating and hot-dried films may be porous after annealing. While spin coating and air-dried films show good quality.At the same time, this thesis also studied the preparation of CdS nanocrystalline thin film by chemical bath deposition (CBD), and the influence of the synthesis temperature, synthesis time and double-layer process on the films. Through the AFM, SEM, XRD test method, we explored surface morphology, crystal structure, transmittance and thickness property of the films. The formation mechanism and the effects of the above variables are explained in the homogeneous and heterogeneous reaction principle. To obtain the best quality of the film, deposition temperature should be80℃and deposition time10min. If the deposition temperature is too low or the deposition time is insufficient, the coverage of the film is not good; while if the reaction time is too long, there will be clusters of particles causing rough surface by attaching to the film. A second short-time deposition can significantly increase the film thickness and crystallinity and reduce the roughness, which has potential applicable value on controlling the thickness and surface uniformity of widely-used CdS.Finally, this thesis studied the preparation of zinc sulfide (ZnS) thin films by chemical bath method. We researched the effect of synthesis time, sodium citrate and doping process, crystalline base and annealing on the thin film. SEM, XRD, UV-Vis and step profiler are used to explore the surface morphology, the crystal structure of the films, transmittance and thickness. And we explain the mechanism of film formation and phenomenon of the experiment. Before50min, deposition is in the induction period and reaction is slow. But when after70min, the reaction is in the mature period. So the choice of60min as the deposition time is the best. Sodium citrate has a little effect on ZnS thin films, only slightly reduce transmittance, increase crystallinity and surface roughness. Boric acid doping can generate its own crystal, also fill in ZnS film’s hole; and the aluminum ions can behydrolyzed in the solution and be heated. They play an important role in delayed release and promote ion attachment to the base. Crystalline base can slightly promote the crystallization of ZnS thin films, and give large particles with a certain orientation. If the films are annealed in500℃for1h, ZnS film can transfer into ZnO and improve the surface flatness.