ECN publication
Title:
Manipulating reverse current in 21% n-MWT cells
 
Author(s):
 
Published by: Publication date:
ECN Solar Energy 14-9-2015
 
ECN report number: Document type:
ECN-M--15-042 Conference Paper
 
Number of pages: Full text:
6 Download PDF  

Abstract:
Metal wrap through (MWT) cells and modules offer technology that combines a front junction cell with an all back contact module interconnection offering potential for higher efficiency, improved cost to power ratio, lower electrical cell to module losses, and improved module aesthetics. For the best conversion efficiency, isolation of the vias for the emitter contacts is key to reduce shunting pathways. However, in reverse bias conditions, the vias are also a controlled current pathway for homogenous dissipation of heat, offering new design opportunities for diode free, shade tolerant modules. We have developed a process for via isolation in high efficiency n-MWT cells where the behavior under reverse bias can be tuned with little impact on illuminated I-V curve and efficiency. We find that after the first exposure to reverse bias, the efficiency of these cells stabilizes and further reverse bias soaking or testing has little impact on performance. Further, these cells were processed into single cell laminates for simulated hot spot testing. The laminates with the highest reverse current performed best under all shading conditions (20%-100%) and were in fact the only laminates that survived all shading conditions without breakage, hot spot development, or significant conversion efficiency reduction.


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