The design and analysis of the mechanism of multi-layered back-contact buffer for CdTe solar cells

Abstract

Back buffer materials play a significant role in improving both open-circuit voltage and fill factor, and developing new materials and structures can be essential for further improvement. In this paper, we have compared the different cases with only one buffer and concluded that single buffer layer always has some innate defects because of the actual constraints. And on the foundation of detailed energy band analysis, we propose that a double- or multi- back buffer structure has the potential to fully mitigate the disadvantage of a single layer and combine the strengths of different materials. The simulation based on this theory demonstrates that the combination of different layers behaves as what we expected and outputs much better performance. It is shown that two layers with reasonable alignment and suitable carrier density are nearly enough for most cases while for extreme cases, more layers are required. Our further simulation provides real designs based on different kinds of back buffer materials, and this work might be instructional for designing new back buffer structures.