Reduction of point defects and Cu surface composition in Cu(In,Ga)Se 2 film by Se annealing with a NaF overlayer at intermediate temperatures
In: Current Applied Physics, Jg. 17 (2017-05-01), S. 820-828
Online
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Zugriff:
Donor-type point defects such as a Se vacancy or cation antisite in Cu(In,Ga)Se2 (CIGS) films were controlled by Se annealing of CIGS film. The photoluminescence intensities originating from such defects were reduced by Se annealing at 300 °C. The short-circuit current of the CIGS solar cell with the Se annealing increased but the fill factor and open-circuit voltage were degraded due to the out-diffusion of Cu from the bulk to the CIGS surface. With a NaF overlayer on the CIGS film the Cu concentration at the CIGS surface was decreased by Se annealing at 300 °C. The literature has demonstrated that the Cu concentration is reduced by applying both NaF and KF together on the CIGS film. However, we found that the application of a NaF overlayer also greatly reduced the Cu concentration at the CIGS surface. In addition, the Na concentration increased greatly at the CIGS surface, forming a desirable surface layer with a lower valence band maximum. As a result, in addition to the increase of short-circuit current, the fill factor and open-circuit voltage increased significantly. The origin of the improvement in cell performance is described by analyzing the point defects from low-temperature photoluminescence, the valence band maximum from x-ray photoelectron spectroscopy, the reverse saturation current from diode curves, and the carrier lifetimes from time-resolved photoluminescence.
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Reduction of point defects and Cu surface composition in Cu(In,Ga)Se 2 film by Se annealing with a NaF overlayer at intermediate temperatures
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Autor/in / Beteiligte Person: | Joong Keun Park ; Kim, Suncheul ; Young Min Ko ; Yong Woo Choi ; Seung Tae Kim ; Byung Tae Ahn |
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Zeitschrift: | Current Applied Physics, Jg. 17 (2017-05-01), S. 820-828 |
Veröffentlichung: | Elsevier BV, 2017 |
Medientyp: | unknown |
ISSN: | 1567-1739 (print) |
DOI: | 10.1016/j.cap.2017.03.009 |
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