Characterization and modeling of Cu(In, Ga)(S, Se)₂‐based photovoltaic devices: A laboratory and industrial perspective

This contribution is a summary of a workshop convened to discuss the characterization and modeling of thin‐film CuInSe₂(CIS)‐based solar cells, 17‐19 October 1993, in Estes Park, Colorado. the participants of the workshop are the authors of this paper. the subject matter was examined along four lines: device modeling, characterization, processing, and manufacturing issues. Fundamental numerical modeling has successfully guided device design efforts, including the design of variable band‐gap absorbers. Quantitative analysis, however, has been compromised by incomplete data on fundamental material properties. Phenomenological modeling and device characterization have sucessfully contributed to the understanding of the device physics. Although classified as a heterojunction device, the forward‐current recombination of the ZnO/CdS/CIS occurs almost exclusively in the space‐charge with diode quality factors ranging from 1.2 to 1.7 for good devices. the next generation of device modeling must incorporate two‐ and three‐dimensional effects. Recent fabrication work has focused on improving the CIS absorber and adding Ga and S to the matrix to increase its band‐gap. A better understanding of the ternary's fundamental properties is required to support the modeling efforts. Control of Ga and S introduction and the resulting absorber band‐gap profiles will facilitate the realization of optimized device designs. Inadequate understanding of fundamental device operation and process control at the laboratory level are amplified in the manufacturing environment. Modeling and characterization can identifv areas where corrective actions will result in improved performance and yield at the module level.