98npe22c09-Development of Advanced Process for the Fabrication of High-Efficiency Cd-Free(II)(III)

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. The Cu(In, Ga)Se2 (CIGS) research teams in Chang Gung University propose a project including seven subprojects to promote the efficiency of CIGS solar cells. This project will cooperate with Nanya Plastic Corporation in developing vacuum and non-vacuum process to fabricate high-efficiency and large-area CIGS solar cells. It is known that a very high efficiency can be achieved by vacuum process with co-evaporation techniques. However, it suffers high cost and large-area uniformity problems. A non-vacuum process with chemical coating has the advantages of low cost and large area capability. In addition, Nanya Plastic Corporation has a very good technique on coating process. Based on Nanya’s expert experiences, this project will focus on chemical coating process to fabricate CIGS solar cells. However, a vacuum process with sputtering techniques is also studied for intermediate phase processing evaluation. To successfully fabricating high efficiency CIGS solar cells, many processing parameters should be taken carefully. The goal would be not attainable if they do not carefully process. We plan seven sub-projects to accomplish the mission goal. The first subject focuses on the study of process parameters for flexible CIGS substrates. The second and third sub-projects investigate how to prepare a very good CIGS absorber layer. A vacuum process with sputtering and selenization are used to fabricate a CIGS absorber layer in the second sub-project. The third sub-project prepares a CIGS absorber layer by non-vacuum process with a chemical solution coating technology. The CdS buffer layer has a pollution problem. A Cd-free buffer for CIGS solar cells is developed in the forth sub-project. The ZnO(i) and ZnO:Al transparent conductive films are investigated by vacuum process in the fifth sub-project and non-vacuum process in the sixth subject. The seventh sub-project is to study the fabrication of ZnO nanotip arrays as antireflection layer to replace traditional MgF2 antireflection layer. In main project work, the integrated 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. In the first year, although the efficiency of our fabricated CIGS solar cells is only 0.8% by sputtering and selenization and 2.3% by chemical solution coating, respectively, the solar efficiency is still increasing toward the first year of 3.5%. The solar efficiency of 11.2% as fabricated by sputtering and selenization with chemical solution coating has been achieved in the second year. To be higher than 15% of sputtering and selenization and 8% of chemical solution coating will be implemented in the third year.

Project ID:PB10103-0042
External Project ID:NSC101-3113-E182-001-CC2