OPTICAL AND ELECTRICAL PROPERTIES OF ZnO/ZnO
Al BILAYERS FOR FRONTAL ELECTRODES IN FLEXIBLE THIN FILM SOLAR CELLS
DOI:
https://doi.org/10.59627/cbens.2016.1438Keywords:
ZnO/ZnO:Al bilayers, flexible substrates, photovoltaic cellsAbstract
Bilayers of ZnO/ZnO:Al thin films were deposited by rf sputtering on polyimide substrates in order to obtain electrical and optical properties suitable for front contacts in flexible CdTe photovoltaic cells. Two polyimide substrates were investigated: Kapton®PV and Kapton®HN. For comparison, films were also grown on glass substrates. The influence of both deposition power and thickness on the film properties was investigated. It was shown that the Kapton®PV is better than the Kapton®HN for superstrate photovoltaic cells, because it is transparent in the whole range of the visible spectrum. The lowest resistance of the ZnO:Al thin films (16-18 Ω/sq) was achieved when the 750nm thick films were deposited at 95W. The average transmittance of the ZnO:Al(750nm)/Kapton®PV configuration was 75%, and was limited by the Kapton®PV substrate. The transmittance was reduced to 68% when a 100nm thick ZnO layer was inserted: ZnO(100nm)/ZnO:Al(750nm)/Kapton®PV. However, the low resistance value of this bilayer configuration - 13 Ω/sq - makes it suitable for use as front electrode in flexible thin film solar cells.
Downloads
References
Fahrenbruch, A.L.; Bube R.H. Fundamentals of solar cells. (1st ed.) Academic Press, New York 1983.
Jäger, S.; Szyszka, B.; Szczyrbowski, J.; Bräuer, G. Comparison of transparent conductive oxide thin films prepared by a.c. and d.c. reactive magnetron sputtering. Surface and Coatings Technology, v. 98, n. 1-3, p. 1304–1314, 1998.
Pearton, S. J.; Norton, D. P.; IP, K.; Heo, Y. W.; Steiner, T. Recent progress in processing and properties of ZnO. Progress in Materials Science, v. 50, n. 3, p. 293–340, 2005.
Perrenoud, J.; Kranz, L.; Buecheler, S.; Pianezzi, F.; Tiwari, A. N. The use of aluminium doped ZnO as transparent conductive oxide for CdS/CdTe solar cells. Thin Solid Films, v. 519, n. 21, p. 7444–7448, 2011.
Sim, K. U.; Shin, S. W.; Moholkar, a. V.; Yun, J. H.; Moon, J. H.; Kim, J. H. Effects of dopant (Al, Ga, and In) on the characteristics of ZnO thin films prepared by RF magnetron sputtering system. Current Applied Physics, v. 10, n. SUPPL. 3, p. S463–S467, 2010.
Szyszka, B.; Loebmann, P.; Georg, A.; May, C.; Elsaesser, C. Development of new transparent conductors and device applications utilizing a multidisciplinary approach. Thin Solid Films, v. 518, n. 11, p. 3109–3114, 2010.
Tiwari, A. N.; Romeo, A.; Baetzner, D.; Zogg, H. Flexible CdTe solar cells on polymer films. Progress in Photovoltaics: Research and Applications, v. 9, n. 3, p. 211–215, 2001.
Wuerz, R.; Eicke, A.; Frankenfeld, M.; Kessler, F.; Powalla, M.; Rogin, P.; Yazdani-assl, O. CIGS thin-film solar cells on steel substrates. Thin Solid Films, v. 517, n. 7, p. 2415–2418, 2009.
