Page 173 - Mirjam-Theelen-Degradation-of-CIGS-solar-cells
P. 173
Degradation mechanisms of the molybdenum back contact
the formation of Na MoO ‘molybdenum bronze’ following this redox reaction:
3
x
+
-
xNa + MoO + xe → Na MoO 3
x
3
+
Intercalation of Na can explain both the high mobility of sodium in the grain
boundaries and the important role this element play in the degradation process. It is
thus proposed that both the grain boundaries as well as the degraded Mo contains
+
+
MoO which is intercalated with Na. Finally the intercalation of Na in MoO is a key
3
3
point in the understanding of the evolution of cell performance under damp heat
exposure in presence of Na. While the MoO is an insulator, NaMoO molybdenum
3
x
3
bronze exhibits occupied states near the Fermi level, making this material conductive.
Therefore, intercalation of Na in the MoO can greatly influence the band alignment
+
3
in CIGS cells, while the formation of non-conductive MoO can completely destroy the
3
solar cell.
5.6 Acknowledgements
We would like to thank Harmen Rooms, Emile van Veldhoven and Arthur Eijk (TNO),
Bertil Okkerse (Philips Innovation Services), Klaas Bakker (ECN) for their assistance with
deposition, measurements or analysis or the fruitful discussions.
5.7 References
[1] T. Wada, N. Kohara, S. Nishiwaki, T. Negami, Thin PVSC (2000) 309-312
Solid Films 387 (1-2) (2001) 118-122. [7] M. Theelen, M. Tomassini, N. Barreau, H. Stei-
[2] D. Fisher, I. Repins, J. Schaefer, M. Beck, W. Batch - jvers, A. Branca, S. Harel S, Z. Vroon, M. Zeman,
th
elor, M. Young, S. Asher, Proc. 31 IEEE PVSC Proc. 38 IEEE PVSC 2 (2012) 1-6
st
(2005) 371-374 [8] M. Theelen, K. Polman, M. Tomassini, N. Barreau,
[3] P. Bommersbach, L. Arzel, M. Tomassini, E. H. Steijvers, J. van Berkum, Z. Vroon, M. Zeman,
Gautron, C. Leyder, M. Urien, D. Dupuy, N. Bar- Surface & Coatings Technology 252 (2014) 157–
reau, Progress in Photovoltaics: Research and 167
Applications 21 (2013) 332-343 [9] M. Theelen, S. Harel, M. Verschuren, M. Tomas-
[4] P. Salomé, V. Fjallstrom, A. Hultqvist, P. Szani- sini, A. Hovestad, N. Barreau, J. van Berkum, Z.
awski, U. Zimmermann, M. Edoff, Progress in Vroon, M.Zeman, submitted toSurface and
Photovoltaics: Research and Applications 22(1) Coatings Technology
(2014) 83-89 [10] J. Scofield, A. Duda, D. Albin, B. Ballard, P. Pre-
[5] M. Powalla, B. Dimmler, Thin Solid Films 387 decki, Thin Solid Films 260 (1995) 26-31
(2001) 251-256 [11] F. Couzinie-Devy, N. Barreau, J. Kessler, Progress
th
[6] J. Wennerberg, J. Kessler, L. Stolt, Proc. 16 EU- in Photovoltaics: Research and Applications 19
171
the formation of Na MoO ‘molybdenum bronze’ following this redox reaction:
3
x
+
-
xNa + MoO + xe → Na MoO 3
x
3
+
Intercalation of Na can explain both the high mobility of sodium in the grain
boundaries and the important role this element play in the degradation process. It is
thus proposed that both the grain boundaries as well as the degraded Mo contains
+
+
MoO which is intercalated with Na. Finally the intercalation of Na in MoO is a key
3
3
point in the understanding of the evolution of cell performance under damp heat
exposure in presence of Na. While the MoO is an insulator, NaMoO molybdenum
3
x
3
bronze exhibits occupied states near the Fermi level, making this material conductive.
Therefore, intercalation of Na in the MoO can greatly influence the band alignment
+
3
in CIGS cells, while the formation of non-conductive MoO can completely destroy the
3
solar cell.
5.6 Acknowledgements
We would like to thank Harmen Rooms, Emile van Veldhoven and Arthur Eijk (TNO),
Bertil Okkerse (Philips Innovation Services), Klaas Bakker (ECN) for their assistance with
deposition, measurements or analysis or the fruitful discussions.
5.7 References
[1] T. Wada, N. Kohara, S. Nishiwaki, T. Negami, Thin PVSC (2000) 309-312
Solid Films 387 (1-2) (2001) 118-122. [7] M. Theelen, M. Tomassini, N. Barreau, H. Stei-
[2] D. Fisher, I. Repins, J. Schaefer, M. Beck, W. Batch - jvers, A. Branca, S. Harel S, Z. Vroon, M. Zeman,
th
elor, M. Young, S. Asher, Proc. 31 IEEE PVSC Proc. 38 IEEE PVSC 2 (2012) 1-6
st
(2005) 371-374 [8] M. Theelen, K. Polman, M. Tomassini, N. Barreau,
[3] P. Bommersbach, L. Arzel, M. Tomassini, E. H. Steijvers, J. van Berkum, Z. Vroon, M. Zeman,
Gautron, C. Leyder, M. Urien, D. Dupuy, N. Bar- Surface & Coatings Technology 252 (2014) 157–
reau, Progress in Photovoltaics: Research and 167
Applications 21 (2013) 332-343 [9] M. Theelen, S. Harel, M. Verschuren, M. Tomas-
[4] P. Salomé, V. Fjallstrom, A. Hultqvist, P. Szani- sini, A. Hovestad, N. Barreau, J. van Berkum, Z.
awski, U. Zimmermann, M. Edoff, Progress in Vroon, M.Zeman, submitted toSurface and
Photovoltaics: Research and Applications 22(1) Coatings Technology
(2014) 83-89 [10] J. Scofield, A. Duda, D. Albin, B. Ballard, P. Pre-
[5] M. Powalla, B. Dimmler, Thin Solid Films 387 decki, Thin Solid Films 260 (1995) 26-31
(2001) 251-256 [11] F. Couzinie-Devy, N. Barreau, J. Kessler, Progress
th
[6] J. Wennerberg, J. Kessler, L. Stolt, Proc. 16 EU- in Photovoltaics: Research and Applications 19
171
