The Fabrication of CIGS Solar Cells Prepared by Sol-Gel Method

Thin film solar cells will consume a little of material and have potentials in low cost, mass production and flexible substrate applications. The most interesting substrates are steel foils, since they can be coated in a roll-to-roll process at high temperatures of up to 600°C in a Se atmosphere. In the last few years, thin film solar cells draw people’s attention due to their great potential application in the future. However, to successfully fabricating high efficiency Cu(In, Ga)Se2 (CIGS) solar cells many processing parameters should be taken carefully. The goal would be not attainable if they do not carefully process. The first challenge is that how the sputtering parameters for depositing the metal molybdenum (Mo) on soda-lime glass should be taken to obtain good adhesion and low sheet resistance. The second is how to prevent the peeling problem in CIGS films by high temperature selenization due to Na-outdiffusion and how to optimize the barrier layer processing. The third is how to adjust the formation composition of CIGS and the selenization process accurately. It will significantly affect solar cell performance. The fourth is how to obtain a very low resistivity film of ZnO by sputtering. Finally, the fifth is how to design contact metal pattern and anti-reflective layer. In our recent work, a good adhesion and low sheet resistance of sputtered Mo film can be achieved by two-stage sputtering with different pressures and r.f. power. In addition, a very low resistivity film of ZnO is also attainable. In this project, we will integrate these process parameters and prepare CIGS absorber by sol-gel process to obtain a high efficiency CIGS solar cell. The important work is how suitably to select sol-solution and gel-solution. In addition, the dispenser is also an important issue. It will affect the rheology of the precursor. The annealing temperature profile is also investigated to obtain a high quality film of CIGO composites. In the reduction processes, it will remove oxygen from the oxide precursor film using H2 gas and expel it as H2O vapors convert the oxide film into a Cu–In–Ga alloy film. The selenization process parameters will be extensively examined by comparing the temperature profiles of two-stage and multi-stage selenization. The optimization of these processes is studied. It is believed that a high efficiency CIGS solar cell can be achieved by integrating and optimizing these process parameters.

Project ID:PB9907-12659
External Project ID:NSC99-2221-E182-052