Research On Non-vacuum Methods To Prepare CZTS Absorption Layer For Solar Cell

Copper zinc tin sulfide(Cu2ZnSnS4, CZTS) is a kesterite structural quaternary compound which belongs to I2-II-IV-VI4 type semiconductor material. CZTS is a P-type direct band gap semiconductor material. It has a high absorption efficiency(up to 104cm-1) and its bandgap(1.5eV) has a good match with sunlight, which makes it suitable absorber layer. Its constituent elements are abundant in the Earth and not harm to natural environment. Therefore, CZTS is the best preference candidate of solar cell absorber materials. Now vacuum methods for preparing CZTS are common synthesis methods to prepare CZTS. But the expensive equipment and complex processes enhance the production costs. While the evaporation rate and sputtering rate of each elemental are different, which makes the process has a poor reproducibility. Thus, non-vacuum methods to prepare CZTS draw more and more attention. If there is a simple, efficient and low-cost mass production way to prepare CZTS film by non-vacuum methods, which is undoubtedly of significant value for solar energy industry and large-scale application. It is the direction of our research that how can we prepared CZTS film by using simple and efficient non-vacuum. According to existing laboratory equipment, we study ways to prepare CZTS by high-energy shock ball milling, screen printing, electrophoresis, and the electrostatic spinning process.(1) High-energy shock ball milling is a way to directly synthesize CZTS nanopowder particles mechanical alloying(MA) by Cu, Zn, Sn, S elemental powders. The particles exhibit a structure of CZTS’s kesterite structure. CZTS nanopowder particles, synthesized by high-energy shock ball milling, provide the material basis of the implementation of the following screen printing process and electrophoresis process.(2) Preparation of CZTS film screen printing is simple, reliable and less affected by parameters. The transparent portion is prepared printed the material onto the substrate. Repeated printing is to get a certain thickness of film. The unwanted organic components of paste are removed by annealing, while allowing the film material has a better crystal growth. Different temperatures make film characteristics different. Slurry-doped antimony(Sb) may be changed to characterize properties of the films.(3) Preparation of a film by electrophoretic has a higher density and deposition rate. But electrophoretic is more sensitive to the parameter. Preparing stable and dense film at a voltage of 18 V after repeated inquiry is excellent. Characterization detected a honeycomb surface rendering. The tabular grains arranged closely. The band gap is 1.5 eV. Phase structure detected many peaks corresponding CZTS’s kesterite structure.(4) Spinning numerous small fibers arranged in a random on the surface of the substrate to form a film by electrostatic spinning. Spinning fiber diameter is about one hundred nanometers. There is less impurity phase. The elemental ratio is more accurate. However, there are many factors affecting spinning. Significantly higher environmental requirements and more operating factors are need than screen printing and electrophoresis,In summary, this paper studys the high energy ball milling, screen printing, electrophoresis, and other non-vacuum technology to prepare CZTS thin-film and successful prepares CZTS film by non-vacuum ways, which provides a feasible technical route to synthesize CZTS.