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P. 220
Chapter 7
7.2.1 Sample analysis
The samples were analysed before and after damp heat-illumination exposure with
optical microscopy, current-voltage (IV) measurements, current voltage measure-
ments as a function of temperature, spectral response (SR) measurements and Sec-
ondary Ion Mass Spectroscopy (SIMS).
Optical microscopy was carried out using a Leica Wild M400 microscope, primarily used at
8x and 64x magnification, coupled with a Leica DFC 320 camera and Leica Application Suite
software, version 4.3.0.
Ex-situ (IV) measurements were obtained using an OAI TriSol Solar Simulator attached
to a KeithleySourceMeter 2400 and controlled using IV runner software, version 1.4.0.6.
The series and shunt resistances are obtained by the determination of the steepness
at the end of the current voltage curves. The SR and therefore also of the external
quantum efficiency (EQE) spectra, were taken using a SR setup. No bias illumination is
used during EQE measurements.
Current voltage measurements as a function of temperature were taken in a Cryostat
Janis VPF-100 with sample holder controlled by a Lake shore 332 temperature
controller. Current voltage curves are obtained with a Keithley Source Meter 2600A
using software in LabView 7.1.
Cross-section scanning electron micrographs were recorded with the FEI XL40 FEG
microscope using backscatter electrons. SEM-EDX measurements in top view were
performed using a JEOL JSM-6010LA IntouchScope.
SIMS depth profiles were performed using a magnetic sector Cameca IMS 7F instrument
in the positive mode, the primary beam intensity was 57nA with 5keV acceleration and
2
it was rastered by 200x200 μm . As a guide for the eye, several SIMS spectra of sodium,
potassium and hydroxide before and after degradation have been multiplied with a
factor close to one along the x-axis to provide better comparison of the spectra.
7.3 Results
7.3.1 Visual changes
Photography and optical microscopy were used in order to study the visual changes
of the surface of the samples. Before degradation, the top surface of all samples
exhibited a homogeneous blue area, as is shown for an alkali-poor sample in Figure
7. 3. Due to damp heat and illumination exposure, small grayish spots occurred on the
top surface of all alkali-rich samples already after 165 hours, while later also white spots
were observed. The spots were ranging in size from about 10 to 150 micrometres. The
top surface of these samples is shown in Figure 7.3.
218
7.2.1 Sample analysis
The samples were analysed before and after damp heat-illumination exposure with
optical microscopy, current-voltage (IV) measurements, current voltage measure-
ments as a function of temperature, spectral response (SR) measurements and Sec-
ondary Ion Mass Spectroscopy (SIMS).
Optical microscopy was carried out using a Leica Wild M400 microscope, primarily used at
8x and 64x magnification, coupled with a Leica DFC 320 camera and Leica Application Suite
software, version 4.3.0.
Ex-situ (IV) measurements were obtained using an OAI TriSol Solar Simulator attached
to a KeithleySourceMeter 2400 and controlled using IV runner software, version 1.4.0.6.
The series and shunt resistances are obtained by the determination of the steepness
at the end of the current voltage curves. The SR and therefore also of the external
quantum efficiency (EQE) spectra, were taken using a SR setup. No bias illumination is
used during EQE measurements.
Current voltage measurements as a function of temperature were taken in a Cryostat
Janis VPF-100 with sample holder controlled by a Lake shore 332 temperature
controller. Current voltage curves are obtained with a Keithley Source Meter 2600A
using software in LabView 7.1.
Cross-section scanning electron micrographs were recorded with the FEI XL40 FEG
microscope using backscatter electrons. SEM-EDX measurements in top view were
performed using a JEOL JSM-6010LA IntouchScope.
SIMS depth profiles were performed using a magnetic sector Cameca IMS 7F instrument
in the positive mode, the primary beam intensity was 57nA with 5keV acceleration and
2
it was rastered by 200x200 μm . As a guide for the eye, several SIMS spectra of sodium,
potassium and hydroxide before and after degradation have been multiplied with a
factor close to one along the x-axis to provide better comparison of the spectra.
7.3 Results
7.3.1 Visual changes
Photography and optical microscopy were used in order to study the visual changes
of the surface of the samples. Before degradation, the top surface of all samples
exhibited a homogeneous blue area, as is shown for an alkali-poor sample in Figure
7. 3. Due to damp heat and illumination exposure, small grayish spots occurred on the
top surface of all alkali-rich samples already after 165 hours, while later also white spots
were observed. The spots were ranging in size from about 10 to 150 micrometres. The
top surface of these samples is shown in Figure 7.3.
218
