Page 242 - Mirjam-Theelen-Degradation-of-CIGS-solar-cells
P. 242
Chapter 8
Abstract
CIGS solar cells were exposed to liquid water purged with the atmospheric gases carbon
dioxide (CO ), oxygen (O), nitrogen (N) and air in order to investigate their degradation
2
2
2
behaviour. The samples were analysed by electrical, compositional and optical
measurements before, during and after exposure in order to follow the degradation
behaviour of these solar cells in time.
The solar cells showed a rapid decrease in conversion efficiency when exposed to water
purged with a combination of CO and N as well as to water purged with air which contains
2
2
O , N ánd CO, while their efficiency was slowly reduced in unpurged water and water
2
2
2
purged with N or O . Cross-section SEM showed that the exposure of samples to H O with
2
2
2
large concentrations of CO led to the dissolution of the ZnO:Al layer, likely starting from the
2
grain boundaries. This resulted in an increased series resistance, which is likely related to an
increase in resistivity of the ZnO:Al layer. It also led to a very rapid decrease of the short circuit
current of these samples. Therefore, the conversion efficiency was rapidly lost.
240
Abstract
CIGS solar cells were exposed to liquid water purged with the atmospheric gases carbon
dioxide (CO ), oxygen (O), nitrogen (N) and air in order to investigate their degradation
2
2
2
behaviour. The samples were analysed by electrical, compositional and optical
measurements before, during and after exposure in order to follow the degradation
behaviour of these solar cells in time.
The solar cells showed a rapid decrease in conversion efficiency when exposed to water
purged with a combination of CO and N as well as to water purged with air which contains
2
2
O , N ánd CO, while their efficiency was slowly reduced in unpurged water and water
2
2
2
purged with N or O . Cross-section SEM showed that the exposure of samples to H O with
2
2
2
large concentrations of CO led to the dissolution of the ZnO:Al layer, likely starting from the
2
grain boundaries. This resulted in an increased series resistance, which is likely related to an
increase in resistivity of the ZnO:Al layer. It also led to a very rapid decrease of the short circuit
current of these samples. Therefore, the conversion efficiency was rapidly lost.
240
