Abstract
CdCl2 activation near 400°C is known to be critically important for obtaining high efficiency CdS/CdTe solar cells. However, this treatment step behaves differently on high-temperature-grown CdTe than on lower-temperature-grown CdTe layers such as those grown by sputtering. On sputtered films, the post-deposition activation produces grain-boundary passivation, sulfur diffusion into CdTe, and substantial grain growth. Nevertheless, we find the CdCl2 process for sputtered films to be characterized by a single activation energy that we interpret as applying to S diffusion into CdTe. We find this activation energy to hold for CdCl2 treatments from 370 to 440°C. The completed CdS/CdTe solar-cell structures showed somewhat poorer initial performance with activation above 420°C, but, in this case, the cell efficiency increased after accelerated life testing at 85°C, open-circuit biasing and one-sun illumination. With an optimized CdCl2 activation process, the use of oxygenated sputtered CdS, and low-iron soda-lime glass, cell efficiencies of 14.5% were achieved.
Original language | American English |
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Article number | 064502 |
Number of pages | 7 |
Journal | Journal of Applied Physics |
Volume | 115 |
Issue number | 6 |
DOIs | |
State | Published - 14 Feb 2014 |
NREL Publication Number
- NREL/JA-5200-61948