TY - JOUR
T1 - Positron Annihilation Studies on the Damp Heat Degradation of ZnO
T2 - Al Transparent Conductive Oxide Layers for CIGS Solar Cells
AU - Shi, Wenqin
AU - Theelen, Mirjam
AU - Illiberi, Andrea
AU - Butterling, Maik
AU - Schut, Henk
AU - Hugenschmidt, Christoph
AU - Zeman, Miro
AU - Bruck, Ekkes
AU - Eijt, Stephan W.H.
AU - More Authors, null
PY - 2018
Y1 - 2018
N2 - Positron annihilation depth-profiling is used as an innovative tool to monitor the evolution of vacancy defects in two series of ZnO:Al transparent conductive oxide (TCO) layers for Cu(In,Ga)Se2 (CIGS) solar cells under accelerated degradation at 85 °C/85% relative humidity. The first series of ZnO:Al layers are deposited directly on flat glass substrates, leading to low densities of (extended) grain boundaries in the ZnO:Al. These ZnO:Al layers only show an increase in open volume upon degradation in the near-surface range. The second series of ZnO:Al layers are deposited on the more corrugated surface of CdS/CIGS/Mo solar cells, and show, on the other hand, a pronounced formation of open volume throughout the layer. Its depth-dependence is consistent with in-diffusion of molecules such as H2O and CO2 into the ZnO:Al layer via the grain boundaries, as primary driver for the degradation. The detected time-dependence of the growth of open volume at the grain boundaries in the ZnO:Al TCO layer matches the time scale of the observed reduction in solar cell efficiency and series resistance, suggesting that the generated open volume induces a significant barrier against charge carrier transport.
AB - Positron annihilation depth-profiling is used as an innovative tool to monitor the evolution of vacancy defects in two series of ZnO:Al transparent conductive oxide (TCO) layers for Cu(In,Ga)Se2 (CIGS) solar cells under accelerated degradation at 85 °C/85% relative humidity. The first series of ZnO:Al layers are deposited directly on flat glass substrates, leading to low densities of (extended) grain boundaries in the ZnO:Al. These ZnO:Al layers only show an increase in open volume upon degradation in the near-surface range. The second series of ZnO:Al layers are deposited on the more corrugated surface of CdS/CIGS/Mo solar cells, and show, on the other hand, a pronounced formation of open volume throughout the layer. Its depth-dependence is consistent with in-diffusion of molecules such as H2O and CO2 into the ZnO:Al layer via the grain boundaries, as primary driver for the degradation. The detected time-dependence of the growth of open volume at the grain boundaries in the ZnO:Al TCO layer matches the time scale of the observed reduction in solar cell efficiency and series resistance, suggesting that the generated open volume induces a significant barrier against charge carrier transport.
KW - Buffer layers, and back contacts
KW - CIGS and CdTe thin film solar cells
KW - degradation
KW - grain boundaries
KW - positrons
KW - transparent conductors
KW - ZnO:Al
UR - http://www.scopus.com/inward/record.url?scp=85051681645&partnerID=8YFLogxK
U2 - 10.1109/JPHOTOV.2018.2863788
DO - 10.1109/JPHOTOV.2018.2863788
M3 - Article
AN - SCOPUS:85051681645
SN - 2156-3381
VL - 8
SP - 1847
EP - 1851
JO - IEEE Journal of Photovoltaics
JF - IEEE Journal of Photovoltaics
IS - 6
ER -