Page 99 - Mirjam-Theelen-Degradation-of-CIGS-solar-cells
P. 99
Experimental information
of the intensity of the light as a function of time and position were both below two
percent, which corresponds to the A qualifications.
The solar cells as described in the previous section are placed in samples holders to
allow electrical contact with the measurement system. Contacting between the cells
and the sample holder is obtained by gold plated contact pens connected on a Printed
Circuit Board (PCB). Figure 3.2c and d show the standard sample holder, as is used for
the reported measurements and the new, improved sample holder respectively. These
contacts allow measurements in a four point probe configuration. This approach was
chosen to minimise the effect of increasing contact resistance on the measurement
due to degradation. Up to twelve holders are then placed on a sample grid, which is
positioned in front of the light source. On the sample grid, twelve thermocouples and
three photodiodes are also present. Figure 3.4 shows this grid with twelve soda lime
glass samples.
A data collection system is positioned outside of the degradation setup to measure
and log IV curves. The system is schematically depicted in Figure 3.1b. The IV curves are
measured by a Keithley 2440 5A source meter. From these data, many characteristics
of the cells or modules can be determined. Since up to twelve cells or modules can
be placed in the chamber simultaneously, a National Instruments PXI-1011 chassis
with multiplexers is connected, allowing all the samples to be measured in turn.
Labview software allows automated logging of the temperature, relative humidity
and light intensity based on three photodiodes, as well as calculation of the electrical
B
C
A
D
Figure 3.4
The sample grid facing the illumination from the solar simulator: A. Photodiode for monitoring of the light intensity
B. Twelve cell holders to measure twelve solar cells simultaneously C. CIGS solar cells with thermocouple D. Wires for connec-
tion with the measurement system
97
of the intensity of the light as a function of time and position were both below two
percent, which corresponds to the A qualifications.
The solar cells as described in the previous section are placed in samples holders to
allow electrical contact with the measurement system. Contacting between the cells
and the sample holder is obtained by gold plated contact pens connected on a Printed
Circuit Board (PCB). Figure 3.2c and d show the standard sample holder, as is used for
the reported measurements and the new, improved sample holder respectively. These
contacts allow measurements in a four point probe configuration. This approach was
chosen to minimise the effect of increasing contact resistance on the measurement
due to degradation. Up to twelve holders are then placed on a sample grid, which is
positioned in front of the light source. On the sample grid, twelve thermocouples and
three photodiodes are also present. Figure 3.4 shows this grid with twelve soda lime
glass samples.
A data collection system is positioned outside of the degradation setup to measure
and log IV curves. The system is schematically depicted in Figure 3.1b. The IV curves are
measured by a Keithley 2440 5A source meter. From these data, many characteristics
of the cells or modules can be determined. Since up to twelve cells or modules can
be placed in the chamber simultaneously, a National Instruments PXI-1011 chassis
with multiplexers is connected, allowing all the samples to be measured in turn.
Labview software allows automated logging of the temperature, relative humidity
and light intensity based on three photodiodes, as well as calculation of the electrical
B
C
A
D
Figure 3.4
The sample grid facing the illumination from the solar simulator: A. Photodiode for monitoring of the light intensity
B. Twelve cell holders to measure twelve solar cells simultaneously C. CIGS solar cells with thermocouple D. Wires for connec-
tion with the measurement system
97
