Programm Photovoltaik Ausgabe 2008 ... - Bundesamt für Energie BFE

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PBDVA
temp
[°C]
100
200
250
Buffer
thickness
[nm]
�
[%]
FF
[%]
Voc
[mV]
Jsc
30 11.7 67.9 623 27.7
CdS-ref. 13.9 72 633 30.5
60 10.1 58.7 633 27.4
CdS-ref. 13.5 73.4 655 27.9
30 11.3 65.4 587 29.5
CdS-ref. 12.4 68.5 618 29.4
60 8.3 55.3 504 29.7
CdS-ref. 13.9 74.1 657 28.6
30 1.4 26.6 247 20.1
CdS-ref. 14.2 74.4 688 28.5
60 4.1 33.5 487 25.4
CdS-ref. 14.2 72.7 685 28.5
[mA/cm 2 ]
Table II: The PV parameters of cells with PBDVA treatment for 10 min at different temperature and
their respective CDB-CdS reference cells.
The buffer layers of ~30 nm and ~60 nm thicknesses were grown on a common absorber obtained
from the same run and no PBDVA treatment was applied. The as-grown cells, with ~30 nm thin buffer
layer yielded an efficiency of 12.1% and with ~60 nm thin buffer produced an efficiency of 12.3%. The
cells were air annealed for 20 min at 200°C resulting in a drop in efficiencies from 12.1% to 10.4% and
from 12.3% to 8.5% for cells with ~30 nm and ~60 nm thin buffer layers, respectively (Table III). But
occasionally efficiency improvement was also measured, which suggests some inconsistencies.
Currently, we are investigating the reasons behind these inconstancies.
A highly efficient cell of 14.1% was realized by depositing ~60 nm thick buffer layer without any
PBDVA treatment. Figure 8 shows the J-V characteristic of such a solar cell. This superior
performance of the cell is attributed to the formation of a high quality buffer layer having lower
stoichiometric disorder and good interface between CIGS-InxSy by diffusion due to chemical potential
difference. However, the efficiency dropped to 13.2% as cell was air annealed at 200°C for 5 min.
Cell
Buffer
thickness
[nm]
�
[%]
FF
[%]
Voc
[mV]
Jsc
As-grown
Air annealed
~30
12.1
10.4
65.9
59.4
631
575
29.1
30.4
As-grown
Air annealed
~60
12.3
8.5
64.9
53.7
666
531
28.3
28.7
CdS-ref. 14.7 75.6 688 28.3
[mA/cm 2 ]
Table III: The PV properties of the cells with ~30 nm and ~60 nm thin InxSy buffer layers grown on a
common absorber. The completed cells were annealed in air for 20 min at 200°C. No PBDVA
treatment was applied.
ATHLET, D. Brémaud, ETH Zurich Seite 101 von 288